Home

context/2 - bei IF Computer

1. Short Execute up to exit of the subgoal Execute up to exit of a subsequent subgoal Execute up to next monitored port Continue to next breakpoint Accelerate execution to exit of the subsequent subgoal Accelerate execution to exit of a subsequent subgoal Continue without stopping Execute up to exit of the subgoal Execute up to exit of a subsequent subgoal Execute up to next monitored port Functionality Display help information Store or append field in previous used file Store field in file Store or append field in file Logging passes through ports Display the goal box in the window Display the clause box in the window Display the goal or clause box in the history list Display the trace field in the window Show dynamic call chain Show dynamic call chain Display default values Display constraints Display list of predicates in module Display list of predicates in module Display listing of a predicate Display listing of a predicate Display explicit breakpoints Display variable constraints Display variable constraints Display help information Store or append field in previous used file Store field in file Reference Manual 626 IF Prolog V5 3 Debugger commands Overview by functionality snapshot File Mode trace view_and_box view_or_box view_history view_trace view_ancestors view_ancestors Number view_configuration view_constraints view_modul
2. The predicate peek_char 1 peeks at the next character from the current input stream cur rent_input and unifies Character with the character read in The predicate peek_char 2 acts in the same way for the specified input stream Stream If the end of the input stream has been reached Character is unified with the atom end_ of_file The predicates can be applied only for text streams see open 3 4 Arguments Stream Stream system defined term or alias atom Character Character or end_of_file Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error input stream The argument Stream is not a stream which has been opened for input open mode read permission_error input binary_stream The current input stream or the argument Stream must be a text stream but is associated with a binary stream permission_error past_end_of_stream The open option eof_action error was set for the input stream Stream and the end of the stream has already been reached system_error read IF Prolog V5 3 397 Reference Manual Elemen
3. BOOLEAN TermIsVar TERM Term The function TermIsVar tests whether the term Term is a Prolog variable If it is the function returns TRUE Otherwise it sets the error context and returns FALSE Arguments Term Term variable Exceptions type_error variable The argument Term must be a variable but is a term of another type See also Term MakeVar IF Prolog V5 3 763 Reference Manual Active C interface C Function TermMakeAtom Generate a Prolog atom include cpred h TERM TermMakeAtom STRING Name The function TermMakeAtom returns a Prolog atom with the name Name Arguments Name Name of the atom Exceptions The following error causes IF Prolog to be exited implementation_error TermMakeAtom out of memory The function TermMakeAtom could not be executed successfully due to a lack of memory See also TermlsAtom Reference Manual 764 IF Prolog V5 3 TermMakeCompound C Function Active C interface Generate a Prolog structure include cpred h TERM TermMakeCompound STRING Functor ARITY Arity The function TermMakeCompound generates a Prolog structure with the name Functor the arity Arity and the arguments and returns it as the result If one of the term variables in is NULL a Prolog variable is generated instead and is used as the structure argument Arguments Functor Character string name of the
4. These commands are used to make the field involved the current field The commands have the following meanings Command Short form Meaning view_and_box amp Display the goal box in the window view_or_box AF Display the clause box in the window view_history vh Display the goal or clause box in the history list view_trace vt Display the trace field in the window Exceptions domain_error arity The command One of the commands was called with an incorrect number of pa rameters Hints These commands are only available in the alpha interface of the debugger Some commands of the alpha interface also effect a change of the display field See also set_history 1 forward backward fast forward fast_backward 0 0 0 0 set_trace length 1 IF Prolog V5 3 671 Reference Manual Command interface Debugger command view_ancestors 0 1 Show dynamic call chain view _ancestors a view_ancestors Number a Number The view_ancestors 0 1 command enables the user to show the current dynamic call chain The output can be restricted to the last Number ancestor s with the Number argument Arguments Number Integer or integer expression Number gt 0 Exceptions instantiation_error The argument Number or a subterm must not be a variable but a variable was specified type_error integer The argument Number must be an integer or an integer expression but is a term of another type
5. 2 698 ErrorContextGet Query error context 0 2 2204 700 ErrorContextIsSet Status of the error context 701 ErrorContextSet Sel error context ca ee be whe wae OS 703 fprintt Formatted output of Prolog terms and C data objects 706 InitProlog Initialize IF Prolog and define the standard media 707 MCPRED Add a complex C function toa module 708 MCPRIM Add a simple C function toa module 709 outputlen Determine length of formatted output 710 ParseError Assignment of syntax error number to syntax error message 711 ParseProlog Parse a goal string and store the information 713 printt Formatted output of Prolog terms and C data objects 715 PrologArg Access predicate arguments ooo a a a 716 PrologClose Deactivate the current Prolog goal 718 PrologEnableEpilog Enable epilog 4 719 PrologError Query enor sors oe ed 6 he bk eh we bE eae Oa e 721 Prologretch Find solutions for a 208 e oe sses edo Siso a krany a aia a 722 PrologG al Prolog goal astern s e s ro oso aak RE owe a YS 723 PrologIsFloat Get floating point number from variable 724 PrologIsInteger Get integer from variable 725 PrologIsString Get character string from variable 726 PrologIsTerm Get Prolog t
6. 587 unix_kill 2 Send signal to a process 6 ee ek ee ee ee es 588 xii unix_make_pipe 1 Create a pipe sik eae ye eee Pe a 590 unix_wait 1 2 Wait for termination of a child process 592 unload 1 Remove module from the database 594 unset_global 1 Delete a global variable 595 user_parameters 1 Query user parameters from IF Prolog call 596 yar 1 Test for yariaDle b e ba ee a e e we oe ee eR ew Re we G 598 windows_chdrive 1 Change drive 020020200 599 windows getdrive 1 Query drive 2 sb ee a es 600 erties 1 2 OUP A teri ee ee eRe Se Re Se Rhee Sw hae ey 601 write_atom 2 Convert aterm into an atom 603 write canonical i gt Output a term os sa cs sasse wee oe es 605 write_formatted 2 3 Formatted output of terms 607 write_formatted_atom 3 Formatted output of terms 611 write term 2 3 Output a fe ok eee eG ee ES 613 writeq 1 2 Output a term in readable form 618 writeq_atom 2 Convert a term into an atom 620 5 Overview by functionality of debugger commands 623 6 Reference section on debugger commands 629 0 0 0 0 Scrolling a ooo a a 630 abort 0 Terminate interactive debugger oaoa a 631 activate_stop 0 1 Reactivate breakpoint 632 back_clause 0 Branch back to clause head oaoa a
7. System statistics statistics statistics Type ResultList The predicate statistics 0 writes system statistics on the output stream current_output The predicate statistics 2 unifies Type and ResultList by backtracking with all the de fined classes of system information and their associated values Type is the system informa tion class and ResultList is a list of the associated values with the format Name Value The following lists are generated depending on Type time cputime Value CPU time used by the IF Prolog process up to now time Value memory System time in seconds system Value database Value Stack Value Size of the memory areas used by IF Prolog system provides information on the total memory usage of IF Prolog database on the usage for the Prolog database and Stack the usage for the individual Prolog stacks Value is unified with a list with the format Total Used where Total is the allocated memory and Used the used memory in bytes Stack is unified with the name of a Prolog stack global constraints local trail extension garbage_collection database Value Stack Value Information on garbage collection database provides information on the garbage collection in the Prolog database Stack provides information on the garbage collection in the individual Prolog stacks global local trail extension Value is unified with a list with the format N
8. Decimal Octal Hexadec Meaning Control 0 00 00 NUL Null no operation 1 01 01 SOH Start of Heading A 2 02 02 STX Start of Text B 3 03 03 ETX End of Text C 4 04 04 EOT End of Transmission END key D 5 05 05 ENQ Enquiry E 6 06 06 ACK Acknowledge F 7 07 07 BEL Bell G 8 10 08 BS Backspace H 9 11 09 HT Horizontal Tabulation I 10 12 0A LF Line Feed J 11 13 0B VT Vertical Tabulation K 12 14 0C FF Form Feed L 13 15 OD CR Carriage Return M 14 16 OE SO Shift Out N 15 17 OF SI Shift In O 16 20 10 DLE Data Link Escape P 17 PA 11 DC1 Device Control 1 Continue output Q 18 22 12 DC2 Device Control 2 R 19 23 13 DC3 Device Control 3 Stop output S 20 24 14 DC4 Device Control 4 T 21 25 15 NAK Negative Acknowledge U 22 26 16 SYN Synchronous Idle V 23 27 17 ETB End of Transmission Block W 24 30 18 CAN Cancel X 25 31 19 EM End of Medium Y 26 32 1A SUB Substitute Character Z 27 33 1B ESC Escape 28 34 1C FS File Separator 29 35 1D GS Group Separator 30 36 1E RS Record Separator 31 37 1F US Unit Separator 827 ASCII table Appendix B Decimal Octal Hexadec Meaning 32 40 20 SP SPACE 33 41 21 34 42 22 R 35 43 23 Number symbol 36 44 24 or national currency symbol 37 45 25 38 46 26 amp 39 47 2T 40 50 28 41 51 29 42 52 2A x Asterisk multiplication sign 43 53 2B 44 54 2C 45 55 2D 46 56 2E 47 57 2F Division sign 48 60 30 0 49 61 31 1 50 62 32 2 51 63 33 3 52 64 34 4 53 65 35 5 54 66 36 6 55
9. Reference Manual 226 IF Prolog V5 3 ensure_loaded 1 Directive Database Insert a Prolog file in the source text once ensure_loaded Filename ensure_loaded Filename The effect of the directive ensure_loaded 1 can be interpreted as the textual replacement of the directive with the Prolog text in the file Filename The directive will be ignored if the same directive with exactly the same Filename as an argument has already been processed The directive ensure_loaded 1 can thus be used to load program text only once Arguments Filename Atom name of a file Exceptions Errors in directives are detected with consult 1 reconsult 1 or compile 1 No exceptions are generated Instead only error messages are output on the current error output stream This directive can produce the following error messages instantiation_error The argument Filename must not be a variable but a variable was specified type_error atom The argument Filename must be an atom but is a term of another type domain_error file_name The value of the argument Filename is not a valid name for a file permission_error open source_sink The argument Filename specifies a file or a different I O medium that cannot be opened system_error read system_error interrupted The error indicated was reported by the operating system when reading the input stream Filename Hints The atom ensure_loaded is defined as a prefix operat
10. Reference Manual 470 IF Prolog V5 3 see 1 Predicate Stream processing Set current input stream see Stream The predicate see 1 makes Stream the current input stream If the argument Stream is not an input output stream and not a defined alias it must be an atom A file of this name is then opened for reading If this succeeds the name is simultaneously registered as an alias for the opened input stream and the stream becomes the current input stream Arguments Stream Stream system defined term alias atom or filename atom Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream domain_error file_name The value of the argument Stream is not a valid name for a file permission_error input stream The argument Stream is not a stream which has been opened for input open mode read permission_error open source_sink The argument Stream specifies a file or a different I O medium that cannot be opened existence_error stream The argument Stream must be associated with an open input output stream Hints All input predicates that have no explicit stream argument refer to the current input stream This stream
11. 2 module 1 import 1 2 export 1 reexport 1 meta 1 Reference Manual 70 IF Prolog V5 3 1 Language construct Execution control Negation through failure Goal Goal The language construct 1 calls Goal and fails if Goal succeeds Otherwise 1 suc ceeds Arguments Goal Goal Exceptions instantiation_error The argument Goal must not be a variable but a variable was specified type_error callable The argument Goal must have the syntactical structure of a Prolog goal existence_error procedure In executing Goal a predicate was to be activated which is not defined and the Prolog flag unknown has the value error type_error atom The argument Goal or a subgoal has been qualified by means of 2 or 2 with a term that is not an atom existence_error module The argument Goal or a subgoal is qualified by means of 2 or 2 with an atom that does not name an existing module Hints The atom is defined as a prefix operator The language construct 1 is identical to not 1 The language construct 1 is not a predicate so it cannot be redefined The pred icates current_predicate 1 and current_visible 2 do not indicate language con structs Explicit module qualification with 2 or 2 is not permitted for language constructs with the exception of cal1 1 The predicates activated in the goal must be visible in the specified Module unless the 2 qualification is use
12. If Length is greater than the length of Atom Prefix is unified with Atom Arguments Atom Atom Length Integer or integer expression Prefix Atom Exceptions instantiation_error The argument Atom or Length must not be a variable but a variable was specified type_error atom The argument Atom must be an atom but is a term of another type type_error integer The argument Length must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer type_error atom The argument Prefix must be a variable or an atom but is a term of another type Furthermore if an arithmetic expression is specified for the argument Length all the exceptions for is 2 can occur Example user atom_prefix file pro 4 B lt ENTER gt B file lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso IF Prolog V5 3 111 Reference Manual String processing Predicate atom_prefix 3 See also atom_concat 3 atom_suffix 3 atom_part 4 getchar 3 index 3 sub_atom 5 atom_split 3 Reference Manual 112 IF Prolog V5 3 atom_split 3 Predicate String processing Decompose an atom atom_split Atom Delimiter Subatoms The predicate atom_split 3 splits Atom into a list of subatoms Subatoms Delimiter is the delim
13. If an expression contains only operators with different precedence the operator with the highest precedence is the main functor of the associated normal structure Expression Associated normal structure 1 2 3 7 01 2 3 7 Begone sd lll Se a Se eh eyed In the second example the comma acting as a functor of a normal structure must be specified in single quotes as the Prolog system will always interpret a comma on its own in this context as a delimiter between the arguments of a structure Associativity of arguments In order to ensure that the association between an expression and the corresponding normal structure is also unique in more general cases the precedence of the terms involved and the precedence for binding associativity of the arguments of an operator are also required The precedence of terms is governed by the following rules e atoms except for operators numbers variables normal structures and lists have the precedence 0 Reference Manual 814 IF Prolog V5 3 Operators Prolog Syntax e terms enclosed in parentheses term have the precedence 0 e expressions not enclosed in parentheses take the precedence of their associated opera tor Besides operator precedence the operator declaration also defines the associativity of the arguments The overview below shows which options Prolog offers f stands for the operator x indicates the position where only an arg
14. Reference Manual 668 IF Prolog V5 3 trace_port 2 Debugger command Command interface Exceptions instantiation_error The argument Ports or Switch or a subterm must not be a variable but a variable was specified type_error atom_or_list The argument Ports must be an atom or a list of atoms but is a term of another type domain_error port The argument Ports is not valid for a port of the box model type_error atom The argument Switch must be an atom but is a term of another type domain_error on_or_off The argument Switch must be one of the atoms on or off but is another atom domain_error arity The command trace_port 2 was called with an incorrect number of parameters See also port 2 IF Prolog V5 3 669 Reference Manual Command interface Debugger command unify 2 Unify variable unify Variable Value Variable Value The unify 2 command can be used to unify a variable in the current clause with a value Arguments Variable Variable Value Term Exceptions type_error variable The argument Variable must be a variable but is a term of another type domain_error arity The command unify 2 was called with an incorrect number of parameters Reference Manual 670 IF Prolog V5 3 view_ 0 Alpha interface Alpha interface Select display fields view_and_box amp view_or_box view_history vh view_trace vt
15. The predicate ground 1 succeeds if TestTerm is ground instantiated i e contains no vari ables otherwise it fails Arguments Test Term Term Example user ground X lt ENTER gt no user ground a b c lt ENTER gt yes user ground a b X d lt ENTER gt no Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also atom 1 atomic 1 compound 1 cyclic 1 float 1 ground 1 integer 1 nonvar 1 number 1 rational 1 var 1 IF Prolog V5 3 289 Reference Manual Execution control Predicate halt 0 1 Terminate Prolog halt halt ExitStatus The predicates halt 0 1 immediately terminate Prolog Any goal execution currently in progress is not completed ExitStatus in halt 1 can be used to send information from the terminated program to the operating system environment as with exit 2 in C Arguments ExitStatus Integer or integer expression Exceptions instantiation_error The argument ExitStatus or a subterm must not be a variable but a variable was specified type_error integer The argument ExitStatus must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer Furthermore if an arithmetic expression is specified for the argument ExitStatus all the exceptions for is 2
16. char_conversion 2 ensure_loaded 1 multifile 1 discontiguous 1 include 1 op 3 dynamic 1 initialization 1 set_prolog_flag 2 Following control constructs are part of the ISO Standard 1 0 call 1 true 0 2 2 catch 3 fail 0 gt 2 throw 1 825 ISO Appendix A Following predicates are part of the ISO Standard at_end_of_stream 0 1 atom_codes 2 atomic 1 bagof 3 clause 2 copy_term 2 current _op 3 current _prolog_flag 2 flush_output 0 1 get_char 1 2 integer 1 nonvar 1 number_codes 2 open 3 4 peek_code 1 2 put_code 1 2 repeat 0 set_output 1 setof 3 unify_with_occurs_check 2 writeq 1 2 D 2 2 gt 2 lt 2 abolish 1 atom 1 atom_concat 3 asserta 1 char_code 2 close 1 2 current_char_conversion 2 current_output 1 findall 3 functor 3 get_code 1 2 is 2 number 1 once 1 peek_byte 1 2 put_byte 1 2 read 1 2 retract 1 set_prolog_flag 2 stream_property 2 var 1 write_canonical 1 2 2 2 lt 2 gt 2 gt 2 arg 3 atom_chars 2 atom_length 2 assertz 1 char_conversion 2 compound 1 current_input 1 current_predicate 1 float 1 get_byte 1 2 halt 0 1 nl 0 1 number_chars 2 op 3 peek_char 1 2 put_char 1 2 read_term 2 3 set_input 1 set_stream_position 2 sub_atom 5 write 1 2 write_term 2 3 Reference Manual 826 IF Prolog V5 3 Appendix B ASCII table
17. gt 2 2 call 1 2 2 set_prolog flag 2 Reference Manual 54 IF Prolog V5 3 lt 2 gt 2 lt 2 gt 2 2 2 Predicate Arithmetic Compare arithmetic expressions Valuel lt Value2 lt Valuel Value2 Valuel gt Value2 gt Valuel Value 2 Valuel lt Value2 lt Valuel Value2 Valuel gt Value2 gt Valuel Value2 Valuel Value2 Valuel Value2 Valuel Value2 Valuel Value2 The comparison predicates are used to compare numeric values A numeric value is a number or an arithmetic expression Arithmetic expressions are evaluated before the comparison is performed The call succeeds if Valuel has the specified relationship to Value2 The names of these predicates are defined as operators with associativity xfx and precedence 700 The table below provides an overview of the function of the predicates Predicate Function succeeds if Valuel is less than Value2 succeeds if Valuel is greater than Value2 succeeds if Valuel is less than or equal to Value2 succeeds if Valuel is greater than or equal to Value2 succeeds if Valuel is equal to Value2 succeeds if Valuel is not equal to Value2 vil VA oA Il a oe I Arguments Valuel Number or arithmetic expression Value2 Number or arithmetic expression IF Prolog V5 3 55 Reference Manual
18. r file st file c file Specify pathname under which the files of the Prolog system are installed This option takes precedence over the pathname given during installation or the environment variable PROROOT If this parameter is not given the pathname defined by the environment vari able PROROOT is used If the environment variable PROROOT is not set the pathname given during installation is used Load system status from file see save_system 1 If file cannot be opened or if file does not have the suffix pst the suffix is appended and the name thus produced is used Independently of its position in the command line this parameter will be evaluated before the system parameters st c and 1 Specify which startup file if any should be loaded or consulted Startup files are loaded or consulted before other files are loaded 1 or consulted c but after a system state has been loaded r If a hyphen is specified for file then no start file is loaded or consulted If the filename file has the suffix pro the file is consulted If it has the suffix cmp it is loaded Otherwise the system tries to consult the file file If the file file does not exist the system tries to append the suffixes pro and cmp and uses the filenames thus produced If this system parameter is omitted and the environment variable PRORC is set the system acts as if st PRORC was given In all other cases the system acts as if st
19. repeat get_char _ at_end_of_line get_char _ yes user read T skip_comment read N lt ENTER gt word Comment lt ENTER gt new_line lt ENTER gt T word N new_line lt ENTER gt yes Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also skip_line 0 1 at_end_of_stream 0 1 Reference Manual 94 IF Prolog V5 3 at_end_of_stream 0 1 Predicate Elementary input output Query end of stream at_end_of_stream at_end_of_stream Stream The predicate at_end_of_stream 0 succeeds if the current input stream current_input is positioned at the end The predicate at_end_of_stream 1 succeeds if the specified input stream Stream is posi tioned at the end An input stream is positioned at the end if a subsequent character read operation would report the end of the input stream Arguments Stream Stream system defined term or alias atom Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream permission_error input stream The argument Stream is not a stream which has been o
20. statistics time S lt ENTER gt S cputime 1 53333 time 774191317 lt ENTER gt yes Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also set_memory_management 3 current memory management 3 is 2 IF Prolog V5 3 531 Reference Manual Stream processing Predicate stream_control 2 Control an input output stream stream_control Stream Command The predicate stream_control 2 enables device dependent control of an I O stream A device driver can provide a set of commands to execute specific operations on I O streams Many built in predicates of IF Prolog make use of these interfaces e g to control the ter minal New device drivers can be linked into IF Prolog using the C driver interface Built in predicates using the control interface of drivers can operate on I O streams for these new device drivers as well provided the required control commands are supported by the drivers The following control commands are implemented in the built in device drivers of the Prolog system Device Command Meaning file stream_type Arg see stream_type 2 stream_size N Unifies N with the size of the file isatty stream_control 2 succeeds if Stream is a terminal fileno N Unifies N with the operating system dependent file number of the file clear_eos see clear_eos 0 1 clear_eol see clear_eol 0 1
21. user listing lt ENTER gt h xxx user portray 2 portray Stream Number integer Number Floating point is float Number writeq Stream Floating point yes user print 3 nl lt ENTER gt 3 0 yes user print 1 2 nl lt ENTER gt 1 0 2 0 yes Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also portray 2 write 1 2 writeq 1 2 write_canonical 1 2 write term 2 3 Reference Manual 412 IF Prolog V5 3 private 1 Directive Module concept Declare predicates as private private PredicateList private PredicateList The directive private 1 is used to declare predicates that are to be defined in the current module This directive must be specified only if a predicate of the same name and same arity was imported by importing a module or if such a predicate is visible in the current module as a result of the implicit importing of system modules Since this directive is executed implicitly by the directives export 1 meta 1 and dynamic 1 it need not be specified again for the predicates declared with these directives The directive private 1 may appear only in the declaration part of a module body Arguments PredicateList List with the format Predicate or structure with the format Predicate Predicate Structure with the format Func
22. 115 atomic 1 Test for constant oee hx BEERS AREER a SEE EES 117 bagof 3 Find selected solutions of a goal oaa aa 118 begin_module 1 Define the body of a module 121 break 0 Generate a new input loop o eoo a a a a 123 byte_length 2 Count the bytes in an atom 124 cali L Qalla goal ga ows a a a oe ES a i ea Koeha a oe e 125 cali z Calla goal eci boo a be ee EDR wR a e a aon BY 127 calling_context 1 Query the module argument of metapredicates 129 cancel_alias 1 Cancel an alias for an input output stream 130 catch 3 Intercept a context JUMP e soes 645 548 moios 4S oe EM 131 char_code 2 Convert between a character and a character code 133 char_conversion 2 Define a character conversion 135 char_conversion 2 Define a character conversion directive 136 ch dir 1 Change current directory 2 kg ee d w bosu dox ee eR e 138 clause 2 Search the database for specific clauses 140 clause_with_names 3 Search the database for specific clauses 142 clear eo1 0 1 Clear to end of lite 4 2 eee ee RR ew DAES eS 144 clear_eos 0 1 Clear to end of screen 2 22000 146 clear_screen 0 1 Clear screen 0 0000 eee 148 close 1 2 Close an input output stream 150 compare 3 Compare terms 2 6 eb be eke ea eee eS 152 compile 1 Compile a Prolog text
23. 2 Predicate Term comparison See also 2 unify_with_occurs_check 2 1 not 1 IF Prolog V5 3 69 Reference Manual Module concept Language construct 2 Specify module context for predicate call Predicate Module Predicate Module This qualification specifies that Predicate is to be called in the context of the module Module i e with Module as the current module This is meaningful only for metapredicates The qualification is ignored for other predicates because it does not matter in which context they are called If a metapredicate is called without this qualification the call takes place in the context of the current module The specified predicate must be visible in the current module unless the defining module for Predicate is specified using as a qualification Predicate must not be a language construct other than cal1 1 2 Arguments Predicate Atom or structure Module Atom name of a module Exceptions The possible errors relating to this notation are detected and reported by IF Prolog during interpretation of a goal cal1 1 or on inclusion in the database asserta 1 2 etc Hints The atom is defined as an infix operator A predicate call cannot be qualified more than once with Standard This language construct is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also
24. IF Prolog V5 3 409 Reference Manual Database Predicate predicate_type 2 type_error integer The arity of the predicate Predicate must be an integer domain_error not_less_then_zero The arity of the predicate Predicate must be a positive integer but is negative representation_error max_arity The arity of the predicate Predicate must be an integer in the range 0 127 but is larger permission_error modify procedure The predicate indicator Predicate specifies a predicate which already exists and is not modifiable or which is the name of a language construct type_error atom The argument Type must be a variable or an atom but is a term of another type Hints Although language constructs such as gt 2 etc are not predicates the type control is returned for them in a type query so that they can be analyzed The predicate predicate_type 2 is a metapredicate and considers only predicate defi nitions which are visible in the calling module or in the specified Module Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also current_predicate 1 current_visible 2 Reference Manual 410 IF Prolog V5 3 print 1 2 Predicate Input output for terms Output a term print Term Module print Stream Term Module The predicates print 1 2 attempt to call the user
25. If Goal does not or does no longer succeed exception_handler 3 fails i e backtracking is initiated If an exception occurs while Goal is being executed and the exception has the information error Error Info which can be unified with Exception then the subgoal which triggered the exception is replaced by Handler and execution is continued Otherwise a search is performed for further active contexts which can handle this exception If no such context can be found exception handling of IF Prolog is carried out i e a context jump is executed see throw 1 Arguments Goal Goal Exception Variable or structure with the format error Term1 Term2 Handler Goal Exceptions instantiation_error The argument Goal or Handler must not be a variable but a variable was specified type_error callable The argument Goal or Handler must have the syntactical structure of a Prolog goal existence_error procedure In executing Goal or Handler a predicate was to be activated which is not defined and the Prolog flag unknown has the value error type_error atom The argument Goal or Handler or a subgoal has been qualified by means of 2 or 2 with a term that is not an atom existence_error module The argument Goal or Handler or a subgoal is qualified by means of 2 or 2 with an atom that does not name an existing module Reference Manual 236 IF Prolog V5 3 exception_handler 3 Predicate Contexts Exceptions domain_
26. If a term is read in successfully VarList is unified with a list of all named variables found in Term and their names in the form Name Variable i e anonymous variables are not included in the list varnames VarList If a term is read in successfully VarList is unified with a list of all variables found in Term and their names in the form Name Variable i e anonymous variables are also included singletons VarList If a term is read in successfully VarList is unified with a list of all variables that occur only once in Term and their names in the form Name Variable Anonymous variables are not included in this list Reference Manual 442 IF Prolog V5 3 read_term 2 3 Predicate Input output for terms Arguments Stream Stream system defined term or alias atom Options List of structures Term Term Flag Atom error quiet fail Vars List of variables VarList List in the form Name Variable Name Atom Variable Variable Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error input stre
27. Query machine identification Query operating system Query system parameters from IF Prolog call Query user parameters from IF Prolog call Change current directory Query and set the editor Edit a file Edit a file Start program execution IF Prolog V5 3 33 Reference Manual Overview by functionality Predicates file_test Pathname AccessMode get_file_info Pathname Attribute Value get_file_info Pathname Info getcwd Dir getenv Name Value localtime Time Year Month Day DoW DoY Hour Min Sec stream_copy Stream1 Stream2 system system Command system Command ExitStatus system Command Input Output system Command Input Output Error Pid timezone Time TimeZone AlternateZone DaylightSaving unix_fork Pid unix_getpid Pid unix_kill Pid Signal unix_make_pipe Pipename unix_wait Pid unix_wait Pid ExitStatus windows_chdrive Drivename windows_getdrive Drivename Processes exec Command exec Prog Args system system Command system Command ExitStatus system Command Input Output system Command Input Output Error Pid Check access permission for a file Get OS information for file Get OS information for file Query current working directory Query environment variable Determine the date and time Redefine streams Start the operating system command interpreter Execute an
28. Reverse a isl ck 2 ee ee Be ee ee wee Se we ee 463 save_module 1 Store current module ina file 465 save_runtime 1 Save system status for creating applications 467 save_system 1 Save current system status 0 469 see 1 Set current input stream 2 0 0 0002s 471 seeing 1 Query current input stream 2 02000 473 seen 0 Reset current input stream o oaoa a 02000 474 select 3 4 5 Synchronous input multiplexing 475 set_array 3 Set array element aoaaa a 477 set_default_module 1 Set current module 479 set_error 1 Set current error output stream o oo 480 set_global 2 Set value of a global variable 482 set_input 1 Set current input stream aoaaa 22 Bed 2 483 set_memory_management 3 Set memory management parameters 484 set_output 1 Set current output stream a oaoa aa a aa 487 set_prolog_flag 2 Set value of a Prolog flag 488 set_prolog_flag 2 Set value of a Prolog flag 493 set_socket_option 3 Set socket option 2 4 495 set_stream_position 2 Position within an input output stream 497 setof 3 Find selected solutions of a goal oaoa a a 499 signal_control 2 Control signal processing ooo a 502 signal_handler 3 Define local signal handling 505 skip line
29. TERM TermMakeVar void The function TermMakeVar generates a new Prolog variable and returns it as the result Exceptions The following error causes IF Prolog to be exited implementation_error TermMakeVar out of memory The function TermMakeVar could not be executed successfully due to a lack of memory See also TermlsVar Reference Manual 776 IF Prolog V5 3 TermOpenList C Function Active C interface Generate a Prolog list include cpred h TERM TermOpenList TERM Tail The function TermOpenList is used to prepare the construction of a Prolog list Technically the function TermOpenList generates a new Prolog variable and stores it in two term variables Tail is initialized with one of these term variables The other term variable is returned as the result Arguments Tail Pointer to a term variable Exceptions The following error causes IF Prolog to be exited implementation_error TermOpenList out of memory The function TermOpenList could not be executed successfully due to a lack of memory Example See example at TermAddList See also TermAddList TermCloseList IF Prolog V5 3 TTT Reference Manual Active C interface C Function TermType Classify term include cpred h TERMTYPE TermType TERM Term The function TermType returns the type of the term Term The function returns the following val
30. The conversion of expressions is governed by the following rules e First the highest precedence number HP of the operators in the expression is deter mined max Precedence fl Precedence fn e If the expression contains only one operator with Precedence f HP then this oper ator is the functor of the associated normal structure e If an expression contains two or more operators with Precedence f HP then the operator types defined for the arguments are used to determine which of these operators is the functor of the associated normal structure e Operands which themselves consist of expressions in parenthesis are evaluated sepa rately Depending on the type of operator involved this determines whether the associated normal structure has an arity of 1 or 2 no other arities are possible Arguments which are in turn expressions are converted into normal structures in analogous fashion 2 5 2 7 2 The following operator definitions apply op 500 yfx op 500 yfx op 400 yfx op 400 yfx The highest precedence number is 500 Since the expression contains two operators with precedence 500 the argument precedence definitions must also be taken into account in order to determine the main functor For the main functor the result would be f the argument in position y would be 2 precedence 0 the argument in position x would be the expression 5 2 7 2 This latter expression contains an
31. atom atom lt ENTER gt yes user atom X lt ENTER gt no user X atom atom X lt ENTER gt X atom lt ENTER gt yes user atom lt ENTER gt yes user atom f a B lt ENTER gt no user atom f a B lt ENTER gt yes Standard This predicate complies with the definition of the ISO standard for Prolog IF Prolog V5 3 97 Reference Manual Term classification Predicate atom 1 See also atomic 1 compound 1 cyclic 1 float 1 ground 1 integer 1 nonvar 1 number 1 rational 1 var 1 Reference Manual 98 IF Prolog V5 3 atom_chars 2 Predicate Term conversion Convert between an atom and individual characters atom_chars Atom List atom_chars Atom List The predicate atom_chars 2 establishes the relationship between an atom and the list com prising of the individual characters of the atom A distinction is made between two cases 1 Atom is instantiated List must be either a variable or a list of variables or characters The predicate atom_ chars 2 creates the list of characters of Atom and unifies the result with List 2 Atom is uninstantiated List must be a completely instantiated list of characters The predicate atom_chars 2 uses List to create an atom the characters of which correspond to the characters in List and unifies the result with Atom Arguments Atom Atom List List of characters Exceptions instantiation_error
32. call 1 current_signal 2 signal_control 2 context 2 set_prolog_flag 2 unix_kill 2 Reference Manual 506 IF Prolog V5 3 skip_line 0 1 Predicate Elementary input output Skip an input line skip_line skip_line Stream The predicate skip_line O reads characters from the current input stream current_input until and including the next end of line character or the end of the stream The predicate skip_line 1 has the same effect but on the specified input stream Stream Arguments Stream Stream system defined term or alias atom Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error input stream The argument Stream is not a stream which has been opened for input open mode read permission_error past_end_of_stream The open option eof_action error was set for the input stream Stream and the end of the stream has already been reached system_error read system_error interrupted The error indicated was reported by the operating system when reading the input stream Stream Example The
33. catch end_of_work gt true Reference Manual 168 IF Prolog V5 3 context 2 Language construct Contexts Exceptions signal user_1 gt work WorkGoal signal user_2 gt throw end_of_work sleep repeat fail work WorkGoal call WorkGoal signal_control user_1 on Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also call 1 catch 3 exception 2 throw 1 exception_handler 3 signal_handler 3 set_prolog_flag 2 IF Prolog V5 3 169 Reference Manual Term conversion Predicate copy_term 2 Create a term copy copy_term Term1 Term2 The predicate copy_term 2 unifies Term2 with a copy of Term in which all the variables have been replaced by new variables Arguments Term1 Term Term2 Term Example user Orig sni Prolog lt ENTER gt write Orig nl lt ENTER gt copy_term Orig Copy lt ENTER gt write Copy nl lt ENTER gt Orig Copy lt ENTER gt sni _69 sni _226 no Identical variables in the term remain identical in the copy user copy_term f A A X lt ENTER gt X Y Z lt ENTER gt Y Z lt ENTER gt A _68 X _76 _76 Y _76 Z _76 lt ENTER gt yes Standard This predicate complies with the definition of the ISO standard for Prolog See also 2 2 Reference Manual 170 I
34. user atom_length X lt ENTER gt X 0 lt ENTER gt IF Prolog V5 3 105 Reference Manual String processing Predicate atom_length 2 yes user atom_length X lt ENTER gt X 2 lt ENTER gt yes Standard This predicate complies with the definition of the ISO standard for Prolog See also atom_concat 3 atom_part 4 atom_suffix 3 atom_prefix 3 getchar 3 index 3 sub_atom 5 byte_length 2 Reference Manual 106 IF Prolog V5 3 atom_number 2 Predicate Term conversion Convert between an atom and a number atom_number Atom Number atom_number Atom Number The predicate atom_number 2 establishes the relationship between an atom and a number A distinction is made between two cases 1 Atom is instantiated Number must be either a variable or a number The predicate atom_number 2 converts Atom to a number and unifies the result with Number 2 Atom is uninstantiated Number must be a number or an arithmetic expression The predicate atom_number 2 converts Number to an atom and unifies the result with Atom Arguments Atom Atom Number Number Exceptions type_error atom The argument Atom must be an atom but is a term of another type representation_error number The argument Atom must be an atom that is representable as a number instantiation_error The argument Number or a subterm must not be a variable but a variable was specified Furthermor
35. write_formatted_atom Atom Format ArgListe open string dummy write S write_formatted S Format ArgListe stream_control S string Atom close S Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1A The predicate write_formatted_atom 3 is new IF Prolog V5 3 611 Reference Manual Formatted input output for terms Predicate write_formatted_atom 3 See also writeq_atom 1 2 write_atom 2 write_formatted 2 3 Reference Manual 612 IF Prolog V5 3 write_term 2 3 Predicate Input output for terms Output a term write_term Term Options Module write_term Stream Term Options Module The predicate write_term 2 outputs Term to the current output stream in a format deter mined by the specified Options The predicate write_term 3 acts in the same way as write_term 2 but writes Term to the specified output stream Stream The following terms can occur as elements of the Options list maxdepth N Limits the structure depth for output to N Any subterms in a structure at a structure depth greater than N are represented by the atom Structure levels are counted starting with 0 Lists are also structures i e N limits the length of lists as well In the case of lists all elements that follow element N in the list counting begins wi
36. Example user yes user yes user no user no user yes user yes user yes adam lt zeppelin lt ENTER gt 3 77 lt 1 lt ENTER gt 13 gt hello lt ENTER gt a x gt b c lt ENTER gt f x lt f y lt ENTER gt g z lt g x y lt ENTER gt f x lt a x y lt ENTER gt Reference Manual 66 IF Prolog V5 3 lt 2 G lt 2 gt 2 gt 2 Predicate Term comparison Standard The predicates lt gt lt and gt comply with the definition of the ISO standard for Prolog See also compare 3 2 2 IF Prolog V5 3 67 Reference Manual Term comparison Predicate 2 Test for non unifiability Term1l Term 2 The predicate 2 succeeds if Term1 and Term2 are not unifiable otherwise it fails Arguments Term1 Term Term2 Term Hints The atom is built in as an infix operator The predicate is semantically identical to Terml Term2 but is not necessarily so defined There is no instantiation of variables Term1 or Term2 Example user X 47 11 lt ENTER gt Y is 47 11 lt ENTER gt X Y lt ENTER gt X 47 11 Y 517 lt ENTER gt yes user a x y a z Y lt ENTER gt Y _71 lt ENTER gt yes user a b X lt ENTER gt no Standard This predicate complies with the definition of the ISO standard for Prolog Reference Manual 68 IF Prolog V5 3
37. Get character string from variable include cpro h BOOLEAN PrologIsString t_cursor ActGoal STRING VarName STRING Name The function PrologIsString checks if the current Prolog goal ActGoal contains a Prolog variable with the name VarName and if this variable is bound to a Prolog atom If such a variable is found the function stores a pointer to the name of the atom in Name and returns TRUE Otherwise the function returns FALSE Arguments ActGoal Structure information on the current Prolog goal VarName Character string name of a Prolog variable Name Pointer to pointer to character See also PrologIsInteger PrologIsFloat ProloglsTerm Reference Manual 726 IF Prolog V5 3 PrologIsTerm C Function Passive C interface Get Prolog term from variable include cpro h BOOLEAN PrologIsTerm t_cursor ActGoal STRING VarName TERM Term The function PrologIsTerm checks if the current Prolog goal ActGoal contains a Prolog variable with the name VarName If such a variable is found the function stores the term bound to this variable in Term and returns TRUE Otherwise the function returns FALSE Arguments ActGoal Structure information on the current Prolog goal VarName Character string name of a Prolog variable Term Pointer to term variable See also PrologIsInteger PrologIsFloat PrologIsString IF Prolog V5 3 727 Reference Manual Passiv
38. If After is set to on no exception will be generated if Predicate is called and is not or no longer defined The call simply fails off the exception existence_error procedure will be generated if Predicate is called and not or no longer defined The Predicate need not yet be defined This attribute is retained beyond abolish 1 Arguments Predicate Structure of the form Functor Arity Functor Atom Arity Integer 0 lt Arity lt 127 Before Atom on off After Atom on off Exceptions instantiation_error The argument Predicate or After or a subterm must not be a variable but a variable was specified type_error predicate_indicator The argument Predicate must be a predicate indicator i e a structure with the format Functor Arity but is a term of another type type_error atom The name of the predicate Predicate must be an atom type_error integer The arity of the predicate Predicate must be an integer Reference Manual 406 IF Prolog V5 3 predicate_mode 3 Predicate Database domain_error not_less_then_zero The arity of the predicate Predicate must be a positive integer but is negative representation_error max_arity The arity of the predicate Predicate must be an integer in the range 0 127 but is larger permission_error modify procedure The predicate indicator Predicate specifies a predicate which already exists and is not modifiable or which is the name of a language construct typ
39. Import predicates import Module import Module import PredicateList from Module import Module PredicateList The directives import 1 2 are used to import predicates from a module The directive import 1 makes all the predicates declared with export 1 in the module interface of Module visible The directive import 2 makes visible only the predicates specified in PredicateList from Module The directive import 1 2 may only occur in the declaration part of a module body and must precede all predicate definitions in the body If the specified Module does not exist yet IF Prolog attempts to read in the module in terface from the file Module mod The file is searched in current search path see set_ prolog_ flag 2 flag search_path If the same predicates are imported from different modules a warning is output In this case an import with import 2 overlays any earlier import whereas a reimport with import 1 is ignored Arguments Module Atom name of a module PredicateList List with the format Predicate or structure with the format Predicate Predicate Structure with the format Functor Arity Functor Atom Arity Integer 0 lt Arity lt 127 Exceptions Errors in directives are detected with consult 1 reconsult 1 or compile 1 No exceptions are generated Instead only error messages are output on the current error output stream This directive can produce the following error message
40. Information on operators Query and set floating point format Define and delete operators Define and delete operators directive User defined output predicate Output a term Output a term Input a term Input a term Query position of a syntax error Reference Manual 26 IF Prolog V5 3 Predicates Overview by functionality read_error Line Column Number read_term Term Options read_term Stream Term Options syntax_error Number Message write Term write Stream Term write_canonical Term write_canonical Stream Term write_formatted Format TermList write_formatted Stream Format TermList write_term Term Options write_term Stream Term Options writeq Term writeq Stream Term Screen control clear_eol clear _eol Stream clear_eos clear_eos Stream clear_screen clear_screen Stream get_last Line Column get_last Stream Line Column move_cursor Line Column move_cursor Stream Line Column tty_size Lines Columns tty_size Q Stream Lines Columns Directives begin_module Module char_conversion CharacterIn CharacterOut Query position of a syntax error Input a term Input a term Assignment of syntax error number to error message Output a term Output a term Output a term Output a term Formatted output of terms Formatted output of terms Output a term Output a term Output a term in read
41. StreamType The predicate stream_type 2 unifies StreamType with the device specific type of the spec ified input output stream Stream The following types are possible for the built in device drivers Device Type file regular block_special character_special directory fifo_special symbolic_link unknown standard regular block_special character_special directory fifo_special symbolic_link unknown pipe pipe string string socket socket null null Arguments Stream StreamType Atom Exceptions instantiation_error Description Regular file Special file Special file Directory Named pipe Symbolic link Unknown type Regular file Special file Special file Directory Named pipe Symbolic link Unknown type Pipe String atom Socket Null device UNIX dev nu11 Stream system defined term or alias atom The argument Stream must not be a variable but a variable was specified IF Prolog V5 3 543 Reference Manual Stream processing Predicate stream_type 2 domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream domain_error stream_control The argument Stream is an input output stream for which the required control co
42. The predicates can be applied only for text streams see open 3 4 Arguments Stream Stream system defined term or alias atom CharCode Integer or integer expression Exceptions instantiation_error The argument Stream or CharCode must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error output stream The argument Stream is not a stream which has been opened for output open mode write or append permission_error output binary_stream The current output stream or the argument Stream must be a text stream but is associated with a binary stream type_error integer The argument CharCode must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer representation_error character_code The argument CharCode must be an integer representing a character code system_error write system_error close Reference Manual 432 IF Prolog V5 3 put_code 1 2 Predicate Elementary input output system_error flush_output system_error interrupted The indicated error was reported by the operating system w
43. The value of the argument Parameter must be a configuration parameter of the Prolog memory management The specified atom is not a valid identifier domain_error on_or_off The argument Value must be one of the atoms on or off but is another atom type_error integer The argument Value must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer domain_error not_less_than_zero The argument Value must be a positive integer but is negative Furthermore if an arithmetic expression is specified for the argument Value all the exceptions for is 2 can occur Hints The values actually set by IF Prolog can deviate from the values specified as arguments due to alignment performed to improve memory usage Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso IF Prolog V5 3 485 Reference Manual Memory management Predicate set_memory_management 3 See also current_memory_management 3 garbage_collection 1 Reference Manual 486 IF Prolog V5 3 set_output 1 Predicate Stream processing Set current output stream set_output Stream The predicate set_output 1 makes Stream the current output stream This stream is used by all output predicates which are specified without an explicit stream argument and is accessible under
44. Value is not changed Arguments Term Term variable Value Pointer to a floating point number Exceptions instantiation_error The argument Term or a subterm must not be a variable but a variable was specified type_error number The argument Term must be a number or an arithmetic expression whose value can be converted implicitly into a floating point number but is a term of another type evaluation_error overflow The argument Term is a number for which an overflow occurred during its implicit conversion into a floating point number See also TermlIsFloat TermIsIntegerExpression TermMakeFloat IF Prolog V5 3 753 Reference Manual Active C interface C Function TermIsFunctor Test for structure include cpred h BOOLEAN TermIsFunctor TERM Term STRING Functor ARITY Arity The function TermIsFunctor tests whether the term Term is a structure with the functor Functor and the arity Arity If it is the function returns TRUE If Term is not a structure or its functor and arity do not match Functor and Arity respec tively the function sets the error context and returns FALSE Atoms are treated like structures with the arity 0 Arguments Term Term variable Functor Character string name of the structure Arity Integer 0 lt Arity lt 127 Exceptions instantiation_error The argument Term must not be a variable but a variable was specified type_error atom_or_compound
45. X C lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also digit 1 current_language 1 set_language 1 Reference Manual 316 IF Prolog V5 3 list_last 2 Predicate List processing Last element in list list_last Element List The predicate list_ast 2 succeeds if Element is unifiable with the last element of List otherwise it fails Arguments Element Term List List Exceptions instantiation_error The argument List or a subterm must not be a variable but a variable was specified type_error list The argument List must be a list but is a term of another type domain_error non_empty _list The argument List must be a non empty list but is empty Hints The predicate is semantically equivalent to the following definition list_last Element List append _ Element List but is implemented more efficiently Example Query the last element of list user list_last X c s c a lt ENTER gt X a lt ENTER gt yes Instantiate the last element of list IF Prolog V5 3 317 Reference Manual List processing Predicate list_last 2 user list_last a c b c X X a lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see
46. day holiday 2 usa 5 6 5 2 9 user likes jones tiger user user jones likes tiger user IF Prolog V5 3 809 Reference Manual Prolog Syntax Terms Expressions Expressions are structures which have an operator as a functor and are specified in operator notation Operator notation is used to specify terms in mathematical notation or to make predi cates clearer and easier to read For example jones likes tiger is easier to read than likes jones tiger and 1 2 more familiar than 1 2 In particular mathematical expressions need not be reformulated prior to input into the unfamiliar normal structure notation Depending on whether the operator is declared as an infix prefix or postfix operator an expression may have the following form argument infix_operator arguments prefix_operator argument argument postfix_operator argument argument are any terms infix_operator is an operator declared with xfx xfy or yfx prefix_operator is an operator declared with fx or fy postfix_operator is an operator declared with xf or yf A number of common operators are declared automatically by the Prolog system A list of these predefined operators can be found in the section 9 3 2 List of built in operators Using op 3 further operators can be declared and canceled again op 3 can also be used to cancel any built in operator declaration At least one delimiter must come between a
47. defined lt atom gt undef ined lt atom gt Reference Manual 14 IF Prolog V5 3 propp System command Prolog system Exceptions Prolog exceptions from file access open read write may occur existence error source_sink The input file does not exist permission error open source_sink The input file cannot be opened for reading The output file cannot be opened for writing domain_error preprocessor_flag Arg An illegal preprocessor flag Arg occurred on the command line domain_error preprocessor_expression Directive An illegal preprocessor directive Directive was encountered domain _error expression Expr The preprocessor expression Expr is malformed type_error atom Name Only atoms are allowed in preprocessor expressions Compatibility V5 1A The command propp is new IF Prolog V5 3 15 Reference Manual Prolog system System command protags Invoke the Prolog tag generator protags Flag Filename Filename The command protags generates a list of tags from Prolog source files and outputs the list on standard output The output can be used as a tags file A tags file gives the locations of specified objects in this case predicates in a group of files Each line of the tags file contains the object name the file in which it is defined and an address specification for the object definition A tags file can be used by some editors UNIX vi and ex to quickly find thes
48. err Error Info The error 2 command is used to raise an exception with the arguments Error and Info in the current subgoal This means that the debugger branches to the ERROR port in the current box Arguments Error Structure or atom Info List of elements like InfoName Wert InfoName Atom Wert Term Exceptions instantiation_error The argument Error or Info or a subterm must not be a variable but a variable was specified type_error list The argument Info must be a list but is a term of another type type_error assignment An element of Info is not an assignment with the format InfoName Wert domain_error arity The command error 2 was called with an incorrect number of parameters See also exit 0 fail 0 predicate exception 2 Reference Manual 642 IF Prolog V5 3 exit 0 Debugger command Command interface Force current subgoal to succeed exit X The exit 0 command is used to force the current subgoal to succeed This may however result in no internal processing of the subgoal being performed This in turn means that variable instantiations or side effects may not take place The debugger branches to the EXIT port in the current box and stops there Exceptions domain_error arity The command exit 0 was called with an incorrect number of parameters See also error 2 fail 0 IF Prolog V5 3 643 Reference Manual Command interface Debugger command fail 0
49. off For consult 1 etc no warnings are output IF Prolog V5 3 191 Reference Manual System information Predicate current _prolog_flag 2 unknown error If a predicate is to be activated which is not defined an exception is raised This does not apply to pred icates for which the exception mode has been set to on see predicate_mode 3 fail If a predicate is to be activated which is not defined backtracking is initiated i e the predicate is evalu ated with fail warning If a predicate is to be activated which is not defined a warning is output and backtracking is initiated i e this predicate is evaluated with fail The warning is not output for predicates for which the exception mode has been set to on see predicate_mode 3 debug on For consult 1 and reconsult 1 all predicates are implicitly declared as dynamic see dynamic 1 to support program testing off For consult 1 and reconsult 1 all the predicates which were not explicitly declared with dynamic 1 are declared as static These cannot then be modi fied tested or displayed prompt on Output of the prompt in the Prolog input loop and interaction for backtracking for goals which have been successfully executed in the Prolog input loop and for which variables have been instantiated always take place i e even if the standard input and the standard output are not terminals off Output of the prompt in the Prolog input loop and interaction for backtracking
50. permission_error output stream The argument Stream is not a stream which has been opened for output open mode write or append Furthermore if an arithmetic expression is specified for the argument Line or Column all the exceptions for is 2 can occur Reference Manual 356 IF Prolog V5 3 move_cursor 2 3 Predicate Screen control Hints The terminal control predicates are implemented via the appropriate stream control functions of the device drivers see stream_control 2 The standard device drivers implement screen control via the terminfo termcap ser vice of the operating system They support only one terminal type for all output streams Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also get_last 2 3 tty_size 2 3 IF Prolog V5 3 357 Reference Manual Database Directive multifile 1 Declare predicates as being scattered over several files multifile PredicateList multifile PredicateList The clauses of predicates declared with the directive multifile 1 can be scattered over several files i e when files are loaded using consult 1 each predicate definition is extended To do this the directive multifile 1 behaves in exactly the same manner as the directive dynamic 1 The directive multifile 1 may only occur in the declaration part of a module body The first multifi
51. user float_format F F lt ENTER gt number_chars 1 2 L lt ENTER gt F g 0 6 L 1 1 9 9 9 9 9 9 9 9 9 9 9 79 9 9 9 lt ENTER gt yes user float_format _ e 0 1 lt ENTER gt float_format F F lt ENTER gt Reference Manual 372 IF Prolog V5 3 number _chars 2 Predicate Term conversion number_chars 1 2 L lt ENTER gt F e 0 1 L 1 7 71 79 9 9 9 9 79 9 9 9 79 9 79 79 9 9 lt ENTER gt yes Standard This predicate complies with the definition of the ISO standard for Prolog The use of arithmetic expressions in the argument Number is not allowed in the ISO standard for Prolog In the ISO compatibility mode see Prolog flag iso therefore no arithmetic expressions may be used as arguments for this predicate Instead an evaluation must be programmed explicitly with the help of is 2 if necessary See also atom_chars 2 number_codes 2 IF Prolog V5 3 373 Reference Manual Term conversion Predicate number _codes 2 Convert between a number and a list of character codes number_codes Number List number_codes Number List The predicate number_codes 2 establishes the relationship between a number and the list comprising of the individual character codes of the number A distincti
52. 3 no If Counter is instantiated it is checked to see whether it lies within the specified range user for 10 3 1 lt ENTER gt yes The predicate for 3 can also be used to create iterative loops by backtracking In the following example goals are read from a file and called Each of these goals must of course have a finite number of solutions otherwise the system will enter an endless loop The input file erample pro contains the following Prolog terms Y is 3 4 write Y nl true fail Calling for 3 will yield the following user open example pro read _ lalias infile lt ENTER gt yes user for 2 X 4 read infile Goal lt ENTER gt write Goal nl lt ENTER gt call Goal fail lt ENTER gt _186 is 3 4 write _186 nl 7 true fail no Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso IF Prolog V5 3 259 Reference Manual Arithmetic Predicate for 3 See also fail 0 repeat 0 is 2 Reference Manual 260 IF Prolog V5 3 functor 3 Predicate Term conversion Generate or analyze a structure functor Structure Functor Arity functor Structure Functor Arity The predicate functor 3 is used to generate a structure or determine the functor and arity of a structure There are two possible cases 1 Structure is not instant
53. 768 774 normal 809 syntax 808 test 157 750 754 761 unify 782 785 790 sublist remove from a list 454 subtraction 309 suffix atom 115 sused 309 Switch off trace mode 667 Switch on trace mode 667 syntax notational conventions 3 syntax analysis string 392 syntax error 440 system parameters query 561 system status load 330 save 467 469 system time 309 tags 16 tail of a list 812 tan 309 tangent 309 tanh 309 term comparison 63 65 convert into atom 603 620 copy 170 formatted output 607 611 input 437 442 last list element 317 list element 324 member of list 344 347 364 ordering 65 output 411 601 605 613 output in readable form 618 read 437 442 syntax 798 test non unifiability 68 IF Prolog V5 3 843 Reference Manual Index type 746 778 unification 58 583 780 792 term context determine 745 release term variables 742 term manipulation add to a Prolog list 738 term variables release 742 Terminate debugger and IF Prolog 646 Terminate interactive debugger 631 terms comparison 152 ordering 152 test for array term 82 for atom 97 for constant 117 for cyclic term 204 for digit 218 for floating point number 252 for instantiation 289 367 for integer 308 for letter 316 for number 370 for rational number 434 for structure 157 for variable 598 time 309 determine 332 570 timezone determine 570
54. Active C interface C Function TermIsNil Test for empty list include cpred h BOOLEAN TermIsNil TERM Term The function TermIsNil tests whether the term Term is the empty list If it is the function returns TRUE Otherwise it sets the error context and returns FALSE Arguments Term Term variable Exceptions instantiation_error The argument Term must not be a variable but a variable was specified type_error list The argument Term must be a list but is a term of another type domain_error list The argument Term must be an empty list but is not empty See also TermlsList TermMakeNil Reference Manual 760 IF Prolog V5 3 TermIsUniversal C Function Active C interface Test for structure include cpred h BOOLEAN TermIsUniversal TERM Term STRING Functor ARITY Arity TERM Args The function TermIsUniversal tests whether the term Term is a structure with the functor Functor and the arity Arity If it is the function initializes the term variables in the vector Args with the term variables contained in the arguments of the structure Term The function returns TRUE If Term is not a structure or its functor and arity do not match Functor and Arity respec tively the function sets the error context and returns FALSE Atoms are treated like structures with the arity 0 Arguments Term Term variable Functor Character string name of the s
55. Arguments Filename Atom name of a file Filelist List of atoms or structures with the form Filename Exceptions type_error list The argument Filelist must be a regular list but is a term of another type or not regular instantiation_error The argument Filename must not be a variable but a variable was specified type_error atom The argument Filename must be an atom but is a term of another type domain_error file_name The value of the argument Filename is not a valid name for a file permission_error open source_sink The argument Filename specifies a file or a different I O medium that cannot be opened system_error read ee nea The error indicated was reported by the operating system when reading the input stream Filename In addition all the error messages and warnings from read_term 2 assertz 1 and assertz_with_names 2 and may occur These do not cause the load process to be aborted You should be aware that the database may not necessarily contain what you expect it to contain Errors in directives are also output as error messages on the error output stream Un known directives are reported by the error message domain_error directive Reference Manual 50 IF Prolog V5 3 2 Predicate Database In the event of errors in a module interface the affected module is deleted after Filename has been processed If there are errors in the declaration part of a module body the affected module body is de
56. IF Prolog V5 3 215 Reference Manual Operating system Predicate default _editor 2 user default_editor _ emacs lt ENTER gt default_editor E E lt ENTER gt E emacs lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also edit 0 1 Reference Manual 216 IF Prolog V5 3 device_control 2 Predicate Stream processing Control an input output device device_control Device Command The predicate device_control 2 enables the stream independent control of input output devices A device driver can provide a number of commands for executing specific operations such as configuration New device drivers can be linked into IF Prolog using the C driver interface The built in device drivers of IF Prolog implement no stream independent control commands Arguments Device Atom name of a device driver Command Term device dependent Exceptions instantiation_error The argument Device or Command or a subterm must not be a variable but a variable was specified type_error atom The argument Device must be an atom but is a term of another type domain_error device_name The value of the argument Device is not an existing device driver type_error atom_or_compound The argument Command must be an atom or a structure but is a term of another type domain_error dev
57. If Filename contains only module interfaces and or bodies then consult 1 and recon sult 1 are prefectly identical The definition of a module interface of an existing module with the same name is first deleted and the definition of a module body overwrites an existing module body The init i directives in Filename are also executed in the context of the relevant module If a module in Filename contains several init 1 directives then the execution sequence is undefined Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also reconsult 1 2 gt 2 IF Prolog V5 3 165 Reference Manual Contexts Exceptions Language construct context 2 Create a context context Goal ContextInfo Module The predicate context 2 is used to create a context for executing Goal the information specified in the list ContextInfo for context global actions is stored in this context Three classes of context global actions are supported 1 Context jumps A context jump similar to longjmp in C enables a context to be exited from any point in a search tree and the entire search tree activated by this context to be rejected at a stroke When the context is exited the actions defined can be executed Context jumps can be initiated by the user throw 1 or they can be executed auto matically in the course of de
58. One or more debugger commands of the command interface can be specified in Actions These commands are executed in sequence at the breakpoint Reference Manual 662 IF Prolog V5 3 stop 4 stop_interactive 1 2 4 Debugger command Command interface Arguments Breakpoint Structure or list with the format e PredicateIndicator e PredicateIndicator ClauseNumber e PredicateIndicator ClauseNumber SubGoalNumber Monitored Variable List of the form PredicateIndicator ClauseNumber Variable PredicateIndicator Structure with the format eFunctor Arity eModule Functor Arity ClauseNumber Integer ClauseNumber gt 0 SubGoalNumber Integer SubGoalNumber gt 0 Ports Atom or list of atoms call enterbody fail failbody failmatch redo redobody suspend trymatch wakeup exit exitbody error all in ner outer c eb f fb fm Ir rb s tm w x xb er Variable Variable BindingType Atom bind modify Conditions Structure with the following format or list with the following optional elements efrequency lt gt lt gt mod Number edepth I lt gt lt gt mod Number erecursion I lt gt lt gt mod Number ematch Head e match Head Body Number Integer or integer expression Number gt 0 Head Term Body Term Actions Atom structure or list of atoms and or structures Debugger commands Exceptions
59. PrologUndo void Construct lists C Function BOOLEAN TermAddList TERM Tail TERM Term BOOLEAN TermCloseList TERM Tail TERM TermMakeList TERM Head TERM Tail TERM TermOpenList TERM Tail Construct Prolog terms C Function TERM TermMakeAtom STRING name TERM TermMakeCompound STRING Functor ARITY Arity TERM TermMakeF loat double Value TERM TermMakeFunctor STRING functor ARITY arity TERM TermMakelInteger long Value TERM TermMakeList TERM Head TERM Tail TERM Term Make Var void Functionality Enable epilog Undo unification Functionality Add to a Prolog list Close a Prolog list Generate a Prolog list Generate a Prolog list Functionality Generate a Prolog atom Generate a Prolog structure Generate a Prolog floating point number Generate a Prolog structure Generate a Prolog integer Generate a Prolog list Generate an empty list Reference Manual 686 IF Prolog V5 3 C interface Overview by functionality TERM TermMakeUniversal STRING Functor ARITY Arity TERM Args TERM TermMakeVar void Device driver function C Function void DeviceCreate t_device Device BOOLEAN StreamFlush t_stream Stream long Number t_iomode StreamMode t_stream Stream Formatted output C Function size_t fprintt FILE FilePointer STRING Format size_t outputlen STRING Format size_t printt STRING Format size_t sprintt char Buffer STRIN
60. Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also read 1 2 read_term 2 3 parse_atom 6 syntax_error 2 IF Prolog V5 3 441 Reference Manual Input output for terms Predicate read_term 2 3 Input a term read_term Term Options read_term Stream Term Options The predicate read_term 2 reads in a term from the current input stream under the control of the specified Options and unifies it with Term The predicate read_term 3 acts in the same way as read_term 2 but reads from the specified input stream Stream If the end of the input stream is reached Term is unified with the atom end_of_file The following control options may be specified as elements of the Options list syntax_errors Flag Determines the behavior of read_term 2 3 when syntax errors occur If this option is omitted the value of the Prolog flag read_error see current_prolog_flag 2 is used The following entries are possible for Flag error An exception is raised quiet No error is reported read_term 2 3 fails fail An error message is output no exception read_term 2 3 fails variables Vars If a term is read in successfully Vars is unified with a list of all named variables found in Term The variables are ordered according to their first occurrence from left to right variable_names VarList
61. Term2 Assignment t TERM terms 2 terms 0 PrologArg 1 terms 1 PrologArg 2 return TermUnifyUniversal PrologArg 3 2 terms void Cbhoot void CPRIM mk_assignment 3 mk_assignment_3 See also TermUnifyCompound TermUnifyFunctor TermUnify TermMakeUniversal IF Prolog V5 3 791 Reference Manual Active C interface C Function Term Unify Var Unify terms include cpred h BOOLEAN TermUnify Var TERM Terml TERM Term2 The function TermUnifyVar unifies Term1 with Term2 If unification is successful the function returns TRUE otherwise it returns FALSE Arguments Term1 Term2 Term variables Hints This function is defined for reasons of orthogonality The call of TermUnifyVar Term1 Term2 is identical to TermUnify Termi Term2 See also Term Unify Reference Manual 792 IF Prolog V5 3 Chapter 9 Prolog syntax Starting from the basic Prolog character set the syntax of Prolog terms is built up step by step in the sections Basic Prolog elements and Terms The remaining parts of this chapter deal with special aspects of operators arithmetic expressions and functions comparison predicates and list processing 9 1 Basic Prolog elements The character set used by Prolog is divided into four classes of characters the Prolog specific characters being of particular importance in the Prolog syntax The remaining characters f
62. The arity of the predicate Predicate in PredicateList must be an integer domain_error not_less_then_zero The arity of the predicate Predicate in PredicateList must be a positive integer but is negative representation_error max_arity The arity of the predicate Predicate in PredicateList must be an integer in the range 0 127 but is larger permission_error modify procedure The predicate indicator Predicate in PredicateList specifies a predicate which al ready exists and is not modifiable or which is the name of a language construct existence_error procedure The argument Predicate in PredicateList specifies a predicate that was not ex ported from the specified module permission_error directive module The specified directive reexport 1 2 is not valid in this position Hints The atom reexport is defined as a prefix operator and the atom from is defined as a infix operator Directives are evaluated during consultation see consult 1 reconsult 1 or compi lation see compile 1 procmp command Standard The directive reexport 1 2 is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also module 1 import 1 2 export 1 meta 1 private 1 IF Prolog V5 3 451 Reference Manual Regular expressions Predicate regexp 2 3 Match a regular expression regexp RegExp Atom regexp RegExp Atom List The predicates regexp
63. The predicate current_alias 2 queries the aliases of input output streams If Alias is instantiated Stream is unified with the input output stream with which Alias is associated If Stream is instantiated Alias is unified by backtracking with all the aliases associated with Stream If both are uninstantiated Alias and Stream are unified by backtracking with all the alias associations known in the system The following aliases are built into the Prolog system Alias Assignment user_input Standard input user_output Standard output user_error Standard error output keyboard Controlling terminal input screen Controlling terminal output current_input Current input current_output Current output current_error Current error output debug_input Used by the debugger debug_output Used by the debugger trace_output Used by the tracer The predicate current_alias 2 succeeds by backtracking for all the alias associations which were defined at the time of the first call even if they have since been deleted or if other associations have been added logic update view Arguments Alias Alias atom Stream Stream system defined term Exceptions type_error atom The argument Alias must be a variable or an atom but is a term of another type Reference Manual 172 IF Prolog V5 3 current _alias 2 Predicate Stream processing domain_error stream The argument Stream must be a variable or an input output stream supplied by open 3
64. but is a term of another type domain_error file_name The value of the argument Pathname is not a valid name for a file type_error list The argument Info must be a variable or a list but is a term of another type type_error atom The argument Attribute must be a variable or an atom but is a term of another type Reference Manual 274 IF Prolog V5 3 get _file_info 2 3 Predicate Operating system Hints To write code that should run under diverse operating systems you can use the predicate system_name 1 to determine the current operating system Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1A The predicates get_file_info 2 3 are new See also file_test 2 system_name 1 IF Prolog V5 3 275 Reference Manual Global variables Predicate get_global 2 Query the value of a global variable get_global Name Value Module The predicate get_global 2 unifies Value with the topmost element of the value stack of the global variable Name in the calling module or in the specified Module The value remains the topmost element in the value stack of global variable Name If the global variable Name is defined with set_global 2 then its value stack comprises just this one value Arguments Name Atom name of a global variable Value Term Exceptions instantiatio
65. clear_screen see clear_screen 0 1 tty_size Z S see tty_size 2 3 move_cursor Z S see move_cursor 2 3 seek P see set_stream_position 2 tell cP see stream_property 2 standard stream_type Arg see stream_type 2 stream_size N Unifies N with the size of the file isatty stream_control 2 succeeds if Stream is a terminal fileno N Unifies N with the operating system dependent file number of the file clear_eos see clear_eos 0 1 clear_eol see clear_eol 0 1 clear_screen see clear_screen 0 1 tty_size Z S see tty_size 2 3 move_cursor Z S see move_cursor 2 3 pipe stream_type Arg see stream_type 2 fileno N Unifies N with the operating system dependent file number of the file Reference Manual 532 IF Prolog V5 3 stream_control 2 Predicate Stream processing socket stream_type Arg see stream_type 2 fileno N Unifies N with the operating system dependent file number of the file string stream_type Arg see stream_type 2 stream_size N Unifies N with the size of the string string Arg Unifies Arg with the contents of the string seek P see set_stream_position 2 tell P see stream_property 2 null stream_type Arg see stream_type 2 get_last Z S see get_last 2 3 Arguments Stream Stream system defined term or alias atom Command Term device dependent Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input ou
66. displayed by listing 0 1 The predicates listing 0 1 only display those predicates for which the list mode is set to on This normally applies only to predicates which have been declared with dynamic 1 or for which the Prolog flag debug was set to on when they were defined Identification of the predicate is based on its visibility in the calling module or in the specified Module The argument Before is unified with the previously valid mode The list mode is then set according to After The list mode can be changed only for predicates for which the modification mode is set to on Like C predicates the built in predicates can never be listed If After is on then listing 0 1 may display this predicate off then listing 0 1 may not display this predicate The predicate Predicate need not yet be defined This attribute is retained beyond abol ish 1 Arguments Predicate Structure with the format Functor Arity Before Atom on off After Atom on off Functor Atom Arity Integer 0 lt Arity lt 127 Exceptions instantiation_error The argument Predicate or After or a subterm must not be a variable but a variable was specified type_error predicate_indicator The argument Predicate must be a predicate indicator i e a structure with the format Functor Arity but is a term of another type IF Prolog V5 3 321 Reference Manual Database Predicate list_mode 3 type_error atom The name of the predicate Predicate must be a
67. domain_error not_less_than_zero The argument Number must be a positive integer but is negative domain_error arity The command skip 0 1 was called with an incorrect number of parameters Furthermore if an arithmetic expression is specified for the argument Number all the exceptions for is 2 can occur See also step 0 continue 0 nonstop 0 fast_skip 0 1 IF Prolog V5 3 657 Reference Manual Alpha interface Alpha interface snapshot 0 1 2 Store field snapshot sn snapshot File sn File snapshot File Mode sn File Mode The snapshot 0 1 2 command writes the current field to a file The entire field in its full length and width is written to the file taking valid structure depth settings into account If Mode is write the previous contents of the file are deleted If Mode is append the field is appended to the file The command snapshot 1 is equivalent to snapshot 2 with Mode write The command snapshot 0 is equivalent to snapshot 2 with Mode append where File refers to the last file opened with snapshot 1 2 Arguments File Atom Mode Atom write append Exceptions instantiation_error The argument File or Mode must not be a variable but a variable was specified type_error atom The argument File or Mode must be an atom but is a term of another type domain_error open_mode The value of the argument Mode is invalid for the mode of a stream permission_error o
68. even if they have since been modified logic update view Arguments Head Structure atom Body Term Exceptions instantiation_error The argument Head must not be a variable but a variable was specified type_error callable The argument Head must have the syntactical structure of a clause head permission_error access static_procedure The argument Head specifies a predicate that was not declared as dynamic type_error callable The argument Body must have the syntactical structure of a Prolog goal Hints Facts in the database have the clause body true The predicate clause 2 is a metapredicate and considers only predicate definitions which are visible in the calling module or in the specified Module Standard This predicate complies with the definition of the ISO standard for Prolog Reference Manual 140 IF Prolog V5 3 clause 2 Predicate Database See also asserta 1 2 assertz 1 2 clause_with names 3 IF Prolog V5 3 141 Reference Manual Database Predicate clause_with_names 3 Search the database for specific clauses clause_with_names Head Body VarList Module The predicate clause_with_names 3 acts in the same way as clause 2 except that any name information on variables is also unified with VarList in the form Name Variable If there is no such information VarList is unified with the empty list The predicate clause_with_names 3 succeeds by backtra
69. instantiation_error The argument or asubterm must not be a variable but a variable was specified type_error predicate_indicator The argument PredicateIndicator must be a predicate indicator with the above mentioned format but is a term of another type IF Prolog V5 3 663 Reference Manual Command interface Debugger command stop 4 stop_interactive 1 2 4 type_error atom The name of the predicate PredicateIndicator or the specified Module must be an atom type_error integer The arity of the predicate PredicateIndicator must be an integer existence_error module The Module specified for the predicate PredicateIndicator does not exist domain_error not_less_then_zero The arity of the predicate Predicatelndicator must be a positive integer but is negative representation_error max_arity The arity of the predicate PredicateIndicator must be an integer in the range 0 127 but is larger existence_error procedure The predicate indicator PredicateIndicator does not specify an existing predicate permission_error access_clause static_procedure The predicate indicator PredicateIndicator specifies a predicate whose clauses can not be accessed permission_error access system_module The predicate indicator PredicateIndicator specifies a predicate whose defining module is a system module type_error integer The argument ClauseNumber must be an integer but is a term of another type domain_error greater_than_zero The arg
70. integer The argument Port must be an integer but is a term of another type type_error atom The argument Filename must be an atom but is a term of another type Reference Manual 516 IF Prolog V5 3 socket_connect 2 Predicate Net communication domain_error file_name The value of the argument Filename is not a valid name for a file existence_error open source_sink The argument Filename specifies a file or a different I O medium that cannot be opened for reading domain_error unix_socket _file The argument Filename must refer to a unix socket file but the file is of another type Hints This predicate is used only in a client process The server process uses the predicates socket_bind 2 and socket_accept 3 If the connection cannot be established due to the exception system_error Connection refused then the application should close the socket using socket_shutdown 1 2 and obtain a new socket with socket 3 before attempting another connection If the socket is not designated as nonblocking see set_socket_option 3 socket_ connect may block further control Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also current_socket 3 socket 3 host_addr 2 net_service 3 socket_accept 3 socket_bind 2 socket_close 1 socket _listen 1 2 socket _receive 2 3 socket_raw_receive 4 5 socket_send 2
71. integer The arity of the predicate Predicate must be an integer existence_error module The Module specified for the predicate Predicate does not exist domain_error not_less_then_zero The arity of the predicate Predicate must be a positive integer but is negative Reference Manual 676 IF Prolog V5 3 view_predicate 0 1 Debugger command Command interface representation_error max_arity The arity of the predicate Predicate must be an integer in the range 0 127 but is larger existence_error procedure The predicate indicator Predicate does not specify an existing predicate permission_error access_clause static_procedure The predicate indicator Predicate specifies a predicate whose clauses cannot be accessed permission_error access system_module The predicate indicator Predicate specifies a predicate whose defining module is a system module existence_error current_predicate The command view_predicate 0 cannot be executed since no current predicate exists domain_error arity The command view_predicate 0 1 was called with an incorrect number of pa rameters Hints The information described here is formatted in accordance with the interface The appearance of the output therefore depends on the interface See also view_module 0 1 IF Prolog V5 3 677 Reference Manual Alpha interface Alpha interface view_ _screen 0 Display history view_previous_screen lt view _last_screen lt
72. lt view _next_screen gt view _first_screen gt gt These commands are used to make the field involved the history field The commands have the following meanings Command Short form Meaning view_previous_screen lt Display the previous goal or clause box view_last_screen lt lt Display the last goal or clause box stored view_next_screen gt Display the next goal or clause box view_first_screen gt gt Display the first goal or clause box stored Exceptions existence_error screen The command view_first_screen 0 view_last_screen 0 view_previous_ screen 0 or view_next_screen 0 cannot be executed since no appropriate screen dump exists domain_error arity The command view_first_screen 0 view_last_screen 0 view_previous_ screen 0 or view_next_screen 0 was called with an incorrect number of param eters Hints These commands are only available in the alpha interface of the debugger See also view_history 0 set_history 1 Reference Manual 678 IF Prolog V5 3 view_stops 0 Debugger command Command interface Display explicit breakpoints view_stops vs The view_stops 0 command displays all explicit breakpoints with all additional information activated or deactivated etc Each breakpoint has a number which can be used to remove activate or deactivate individual breakpoints Exceptions domain_error arity The command view_stops 0 was called with an incorrec
73. not available in ISO compatibility mode see Prolog flag iso See also move_cursor 2 3 Reference Manual 278 IF Prolog V5 3 get _socket_option 3 Predicate Net communication Get socket option get_socket_option Socket Option Value The predicate get_socket_option 3 gets the current state of an option of a socket The argument Socket must be a term representing a socket The arguments Option and Value are unified by backtracking with the supported option names and their values The set of supported options and corresponding values is system dependent The following table contains the allowed values for Option The predicate get_socket_option 3 fails if the given option Option is not supported for the underlying operating system Option Explanation Type of Value broadcast Transmit broadcast messages on off close_on_exec Control take over of current sockets on off debug Record debugging information on off dontroute Routing bypass for outgoing messages on off error Get and clear error atom keepalive Keep connections alive on off nonblocking Make socket asynchroneous synchroneous on off oobinline Reception of out of band data on off linger Linger on close if data present integer revbuf Size of input buffer integer reuseaddr Local address reuse on off reuseport Local port reuse on off selectread Designate socket for reading on off selectwrite Designate socket for writing on off sn
74. page 812 the predicate fails If Head and List are uninstantiated variables an infinite number of solutions may be generated by backtracking Under certain circumstances List may be instantiated to any term For example append term term succeeds IF Prolog V5 3 77 Reference Manual List processing Predicate append 3 Example This simply checks that appending a b and c d results in the list a b c d user append a b c d la b c d lt ENTER gt yes If the tail of the list a b c d is instantiated to c d then a b is the only possible head There are no alternatives user append X c d a b c d lt ENTER gt X a b lt ENTER gt no One very important application of append 3 is the generation of all possible ways of decomposing a list user append X Y a b lt ENTER gt X Y a b lt ENTER gt X a Y b lt ENTER gt X a b Y lt ENTER gt no Although rarely used it is permissible to append an atom or any other term to a linear list The appended term appears as the tail in the result list user append a b c f a b X lt ENTER gt X a b clf a b lt ENTER gt yes This may mean that List is instantiated to any term user append x y EL lt ENTER gt EL x y lt ENTER gt yes Reference Manual 78 IF Prolog V5 3 append 3 Predicate List processing The predicate append 3 can also b
75. static long counter 0 return TermUnifyInteger PrologArg 1 countert void Cboot void CPRIM counter 1 counter_1 Reference Manual 716 IF Prolog V5 3 PrologArg C Function Active C interface See also TermArg IF Prolog V5 3 717 Reference Manual Passive C interface C Function PrologClose Deactivate the current Prolog goal include cpro h void PrologClose t_cursor ActGoal The function PrologClose releases the current Prolog goal see functions PrologOpen or QueryOpen and all appropriate resources The goal which was current before the creation of ActGoal becomes the current goal again Arguments ActGoal Structure information on the current Prolog goal Hints The structure ActGoal is undefined after the call of PrologClose See also PrologOpen QueryOpen PrologFetch Reference Manual 718 IF Prolog V5 3 PrologEnableEpilog C Function Active C interface Enable epilog include cpred h void PrologEnableEpilog void The function PrologEnableEpilog defines that a complex C function has an epilog This epilog will be called as soon as the complex C function can find no more solutions Manipulations of terms is not allowed during execution of an epilog The term arguments of the complex C function are not defined during the execution of the epilog The function PrologEnableEpilog must be called at
76. toplevel generate 123 return to 75 trace goal 573 tracer configure 576 initialize 575 output predicate 579 termination 578 trail stack size 309 used 309 transform term grammar rules 240 truncate 309 TRYMATCH port 634 tsize 309 tused 309 type operator 813 undo unification 730 unification term 58 583 term with atom 781 term with floating point number 784 term with integer 787 term with list 788 term with structure 782 785 790 term with term 780 792 term with the empty list 789 undo 730 with occurs check 583 Unify variable 670 univ 60 uppercase letters convert to lowercase 334 user parameters query 596 variable anonymous 806 free 118 499 generate 776 global 806 single variable check 806 syntax 804 test 598 763 variable name 805 version of IF Prolog system 425 wait for end of process 592 Reference Manual IF Prolog V5 3
77. type_error integer The argument Port must be a variable or an integer but is a term of another type type_error atom The argument Filename must be a variable or an atom but is a term of another type type_error list The argument List must be a variable or a list but is a term of another type type_error integer The argument Length must be a variable or an integer but is a term of another type Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1B The predicates socket_raw_receive 4 5 are new See also socket 3 current _socket 3 select 3 host_addr 2 net_service 3 set_socket_option 3 socket_accept 3 socket_bind 2 socket_connect 2 socket_close 1 socket _listen 1 2 socket_send 2 3 socket_shutdown 1 2 Reference Manual 520 IF Prolog V5 3 socket_receive 2 3 Predicate Net communication Receive data from socket socket_receive Socket List socket_receive Socket Addr List The predicates socket_receive 2 3 receive data from a socket The predicate socket_ receive 2 receives data from a connected socket see socket_connect 2 and socket_ accept 3 The predicate socket_receive 3 receives a datagram from any address The argument Socket must be a term representing a socket The argument Addr of socket_receive 3 is unified with the address from w
78. warnings are output as a function of the Prolog flag warnings in certain situations to alert you to possible sources of errors Hints The name of the file which contains the compiled Prolog text is Filename with the extension pro being replaced by the extension cmp if there is no extension cmp is simply added to the filename Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also load 1 unload 1 save module 1 Reference Manual 156 IF Prolog V5 3 compound 1 Predicate Term classification Test for structure compound TestTerm The predicate compound 1 succeeds if TestTerm is a structure otherwise it fails Arguments Test Term Example user yes user yes user yes user no user yes user yes user yes Term compound a _ _ lt ENTER gt compound a b lt ENTER gt compound a b lt ENTER gt compound a lt ENTER gt X a b c d e f lt ENTER gt compound X lt ENTER gt a x b c d _ e lt ENTER gt compound not true lt ENTER gt compound a b lt ENTER gt The empty list is not a structure it is an atom IF Prolog V5 3 157 Reference Manual Term classification Predicate compound 1 user compound lt ENTER gt no Standard This predicate complies with
79. 0 1 lap an input limes pse c se soes eo Be ew SS eB 507 socket 3 Create communication socket o oo aa a a 000 509 socket_accept 3 Accept a connection 4 511 socket_bind 2 Bind a name toa socket 2024 513 socket_close 1 Close asocket 02 2 0000 eee 515 socket_connect 2 Connect a socket 0 0 0 000202 ee 516 socket_listen 1 2 Listen for connections 518 socket_raw_receive 4 5 Receive data from socket 519 socket_receive 2 3 Receive data from socket 521 socket_send 2 3 Send data to socket 0 2 020005 523 socket_shutdown 1 2 Close a socket sc c scopo sereo eds irur 525 Sort 2 DOM a late ele ee eS a e g ee oe a Re e aw 4S 527 statistics System statistics o ss c s acoes a bire aa kone ah 529 xi stream_control 2 Control an input output stream 532 stream_copy 2 Redefine streams 00 0 2 0 es 535 stream_device 2 Determine device name of an input output stream 538 stream_property 2 Query information on input output streams 540 stream_type 2 Query type of an input output stream 543 sub atan S Analyze an atom i e c koe aa wR REDO OER ee DS 545 syntax_error 2 Assignment of syntax error number to error message 548 system 0 Start the operating system command interpreter 550 system 1 2 Execute an operating s
80. 1 or compile 1 when a Prolog source text is read and takes effect immediately Arguments Priority Integer or integer expression 0 lt Priority lt 1200 Assoc Atom xf yf fx fy xfx xfy yfx Names Atom or list of atoms Exceptions Errors in directives are detected with consult 1 reconsult 1 or compile 1 No exceptions are generated Instead only error messages are output on the current error output stream This directive can produce the following error messages instantiation_error The argument Priority Assoc or Names or a subterm must not be a variable but a variable was specified type_error integer The argument Priority must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer domain_error operator_priority The argument Priority is not in the prescribed range of values for the precedence of operators type_error atom The argument Assoc or an element of Names must be an atom but is a term of another type domain_error operator_specifier The argument Assoc is not a valid type for an operator definition type_error list The argument Names must be a regular list or an atom but is a term or another type or not regular IF Prolog V5 3 383 Reference Manual Input output for terms Directive op 3 permission_error modify operator The argument Names specifies an existing operator whose definition is incompat
81. 2 IF Prolog V5 3 355 Reference Manual Screen control Predicate move_cursor 2 3 Position the cursor move_cursor Line Column move_cursor Stream Line Column The predicate move_cursor 2 moves the cursor to the specified Line and Column position of the screen associated with the current output stream The predicate move_cursor 3 acts in the same way as move_cursor 2 but uses the screen associated with the specified output stream Stream If there is no screen associated with the current output stream or if the device driver is able to execute this operation the predicate has no effect but the call succeeds nevertheless Arguments Stream Stream system defined term or alias atom Line Integer or integer expression Column Integer or integer expression Exceptions instantiation_error The argument Stream Line or Column must not be a variable but a variable was specified type_error integer The argument Line or Column must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream
82. 2 Convert between a number and a list of characters number_codes 2 Convert between a number and a list of character codes once 1 Activate a goal once only s sao ooo o oa a op 3 Define and delete operators ooo a op 3 Define and delete operators directive 0 open 3 4 Open an input output stream outtab 1 2 Position the curser sioe aes Bae ee wee SD eee SS parse_atom 6 Parse a character string in accordance with Prolog syntax peek byte 1 2 Input a byte a ce eee ee Ha eee ae Ree Be we peek char 1 2 Input a haracter icc he RD oe eke Ee ES peek_code 1 2 Input acharacter 0 52 200 phrase 2 Call a grammar rule 2 ed ee hoe eh ee oe ed pop_global 2 Query global variable and remove value portray 2 User defined output predicate 2 24 4 predicate_mode 3 Query and set the exception mode of a predicate predicate_type 2 Query predicate type 04 print We i put aterm e Ge hk uian eee ee ees oe ES private 1 Declare predicates as private 204 profile 1 2 Activate profiling fora goal 1x profile_reset 0 Reset profiling statistics 0 4 417 profile_stat 0 1 Query profiling statistics 418 program 0 Automatically call a Prolog goal 420 program_parameters 1 Query parameters
83. 2 List of built in operators The following table is an overview of the built in operators Reference Manual 818 IF Prolog V5 3 Operators Prolog Syntax Operator Prec Type Pred Func Meaning i 1200 xfx Separates clause head and body of a clause gt xfx Generation of syntax rules fx Identifies a directive fx Prompt 1100 xfy Pred Disjunction of goals gt 1050 xfy Pred Conditional if gt then ar 1000 xfy Pred Conjunction of goals not 900 fy Pred Negation through failure 900 fy Pred Negation through failure gt 900 xfx Context info is 700 xfx Pred Evaluate arithmetic expression xfx Pred Convert between a structure and a list gt xfx Pred Comparison predicates lt xfx Pred for terms gt xfx Pred lt xfx Pred xfx Pred xfx Pred gt xfx Pred Comparison predicates lt xfx Pred for numeric values gt xfx Pred lt xfx Pred xfx Pred xfx Pred xfx Pred Test for non unifiability xfx Pred Unification 500 yfx Func Logical OR yfx Func Logical AND yfx Func Logical XOR yfx Func Addition yfx Func Subtraction 400 yfx Func Division yfx Func Integer division yfx Func Multiplication rem yfx Func Remainder mod yfx Func Modulo gt gt yfx Func Binary shift right lt lt yfx Func Binary shift left 200 fx Func Logical complement yfx Func Exponentiation fx Func Neutral function fx Func Nega
84. 244 propp Invoke the Prolog preprocessor 24 see Bae ew ee ee es protags Invoke the Prolog tag generator 2 proxref Invoke the Prolog cross referencer Overview by functionality of predicates Reference section for the predefined predicates 170 Disable backtracking lt lt ov ci 2G 4 Rw EER Rw R ERE we EEE OY fot mm Ho Of PORN es oe ce ne ee ce Se ee Ee Sw Sw a 3 2 Create a grammar PING sa de e a ee e Ree eR ee ew ee gt 2 IF THEN conjunction of goals sss ebe be ee Re oe ew g 2 List notation for consult 1 reconsult 1 2 Specify the module of the called predicate p2 Disjunctiom of goals s4 s sda sta doa Eana g EE we goard lt 2 gt 2 lt 2 gt 2 2 2 Compare arithmetic expressions iii iii oO N Q OHO 13 14 16 17 19 37 39 42 44 47 50 52 53 55 ya Viy Geli a e e a a RR BES we EAE Sw Od oS 2 Convert between a structure and a list 2 2 Compare terms for identity ooo lt 2 lt 2 gt 2 gt 2 2 2 Compare terms 2 Test for non mifiability 2 6 4 saci eno sat ee EER eG REE Ee 2 Specify module context for predicate call Ah Negation throne b failure eos e oe we eh ee eee ee ge oS es abolish 1 Remove a predicate from the database abort 0 Return to the top
85. 3 4 Arguments Stream Stream system defined term or alias atom CharCode Integer Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error input stream The argument Stream is not a stream which has been opened for input open mode read permission_error input binary_stream The current input stream or the argument Stream must be a text stream but is associated with a binary stream permission_error past_end_of_stream The open option eof_action error was set for the input stream Stream and the end of the stream has already been reached system_error read ie neal The error indicated was reported by the operating system when reading the input stream Stream IF Prolog V5 3 399 Reference Manual Elementary input output Predicate peek_code 1 2 type_error integer The argument CharCode must be a variable or an integer but is a term of another type representation_error in_character_code The argument CharCode must be a variable an integer representing a character code or the integer 1 representation_error charact
86. 52 IF Prolog V5 3 oy Language construct Execution control Disjunction of goals t Goall Goal2 Goall Goal2 The language construct 2 is used to combine two goals to form a composite goal The new goal succeeds if Goall succeeds or if it does not or does no longer succeed if Goal2 succeeds The subgoal Goal2 is therefore only executed if Goall does not or does no longer succeed If Goall or Goal2 are re executable they can return several results Backtracking takes place first in Goall and if that is not or no longer possible in Goal2 If subgoal Goall is a composite goal produced with gt 2 then 2 has a different effect from the one described above This combination resembles the if then else constructs of other programming languages and is described under gt 2 Arguments Goall Goal Goal2 Goal Exceptions instantiation_error The argument Goall or Goal2 must not be a variable but a variable was specified type_error callable The argument Goall or Goal2 must have the syntactical structure of a Prolog goal existence_error procedure In executing Goall or Goal2 a predicate was to be activated which is not defined and the Prolog flag unknown has the value error type_error atom The argument Goall or Goal2 or a subgoal has been qualified by means of 2 or 2 with a term that is not an atom existence_error module The argument Goall or Goal2 or a subgoal is
87. 67 37 T 56 70 38 8 57 71 39 9 58 72 3A 59 73 3B 60 74 3C lt 61 75 3D 62 76 3E gt 63 77 3F Reference Manual 828 IF Prolog V5 3 Appendix B ASCII table Decimal Octal Hexadec Meaning 64 100 40 commercial at or 65 101 41 66 102 42 67 103 43 68 104 44 69 105 45 70 106 46 71 107 47 72 110 48 73 111 49 74 112 4A 75 113 4B 76 114 4C TT 115 4D 78 116 4E 79 117 4F 80 120 50 81 121 51 82 122 52 83 123 53 84 124 54 85 125 55 86 126 56 87 127 57 88 130 58 89 131 59 90 132 5A 91 133 5B wT NKR MS SGCHMODOTVOSZEZMACTEOAAIAWe O 92 134 5C Backslash 93 135 5D 94 136 5E 95 i 5F Underscore IF Prolog V5 3 829 Reference Manual ASCII table Appendix B Decimal Octal Hexadec Meaning 96 140 60 97 141 61 98 142 62 99 143 63 100 144 64 101 145 65 102 146 66 103 147 67 104 150 68 105 151 69 106 152 6A 107 153 6B 108 154 6C 109 155 6D 110 156 6E 111 157 6F 112 160 70 113 161 71 114 162 72 115 163 73 116 164 74 117 165 75 118 166 76 119 167 77 120 170 78 121 171 79 122 172 7A 123 173 7B 124 174 7C 125 175 7D 126 176 TE 127 177 TF DEL Delete Interrupt Signal WANS KH ESE atan aAa O B RTA Sw mmeo Aaa Th Reference Manual 830 IF Prolog V5 3 Appendix C Glossary alias name argument arity atom backtracking body box model Atom associated with an open stream An object in a Prolog structure In the term mother
88. 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 yes Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also system 0 3 5 halt 0 1 IF Prolog V5 3 553 Reference Manual Operating system Predicate system 3 5 Execute an operating system command with input and output spec ified system Command Input Output system Command Input Output Error Pid The predicate system 3 executes Command in an operating system shell using the specified I O streams Input and Output as the standard input and standard output of the Command This makes it possible to supply inputs to a command from IF Prolog and to process outputs from a command within IF Prolog If Input is a variable the system creates and opens a pipe whose input direction becomes the standard input of Command and whose output direction is bound to this variable as a IF Prolog output stream All subsequent outputs on this output stream are sent to the specified Command as inputs If Output is a variable the system creates and opens a pipe whose output direction becomes the standard output of Command and whose input direction is bound to this variable as a IF Prolog input stream All outputs from Command are then available as inputs on this input stream The predicate system 5 is functionally equivalent
89. Arithmetic Predicate lt 2 gt 2 lt 2 gt 2 2 2 Exceptions instantiation_error The argument Valuel or Value2 or asubterm must not be a variable but a variable was specified Furthermore if an arithmetic expression is specified for the argument Valuel or Value2 all the exceptions for is 2 can occur Hints Due to the limited precision when calculating with floating point numbers a comparison of arithmetic expressions does not always yield the mathematically correct result Since different computers have different levels of precision the same comparison of arithmetic expressions when performed on different computers may lead to conflicting results so it is best to avoid checking floating point numbers for precise equality Example Testing two numbers for less than relationship user X 12 Y 17 X lt Y lt ENTER gt X 12 y 17 lt ENTER gt yes Testing two numbers for greater than relationship user X 12 Y 15 X gt Y lt ENTER gt no Testing two numbers for less than or equal to relationship user X 20 Y 12 X lt Y lt ENTER gt no Testing two numbers for greater than or equal to relationship user X 12 Y 12 X gt Y lt ENTER gt X 12 Y 12 lt ENTER gt yes Reference Manual 56 IF Prolog V5 3 Arithmetic lt 2 gt 2 lt 2 gt 2 2 2 Predicate Testing two numbers
90. Clause asserta Head Body asserta_with_names Clause VarList asserta_with_names Head Body VarList assertz Clause assertz Head Body assertz_with_names Clause VarList assertz_with_names Head Body VarList compile Filename consult Filename ensure_loaded Filename include Filename load Filename load_system Filename Reexport predicates Store current module in a file Set current module Remove module from the database Create a grammar rule Transform a grammar rule Call a grammar rule List notation for consult 1 List notation for reconsult 1 Remove a predicate from the database Insert a clause in the database Insert a clause in the database Insert a clause in the database Insert a clause in the database Insert a clause in the database Insert a clause in the database Insert a clause in the database Insert a clause in the database Compile a Prolog text Read in a Prolog file Insert a Prolog file in the source text once Include a Prolog file in the source text Load compiled Prolog text Restore the old system status IF Prolog V5 3 29 Reference Manual Overview by functionality Predicates reconsult Filename retract Clause retract Head Body retract_with_names Clause VarList retract_with_names Head Body VarList save_runtime Filename save_system Filename Query database clause Hea
91. ENTER gt user 3 abort lt ENTER gt abort user Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also break 0 throw 1 IF Prolog V5 3 75 Reference Manual Contexts Exceptions Predicate alarm 1 Schedule alarm alarm Seconds The predicate alarm 1 causes the system to send the calling process an alarm signal after the number of real time seconds specified by Seconds have elapsed Processor scheduling delays may prevent the process from handling the signal as soon as it is generated If Seconds is negative or zero a pending alarm request if any is cancelled Alarm requests are not stacked only one alarm generation can be scheduled in this manner If the alarm signal has not yet been generated the call will result in rescheduling the time at which the alarm signal will be generated The current handling mode for the alarm can be queried with the predicate current_ signal 2 and changed with signal_control 2 It is recommendable to activate either the active on or the passive off signal handling mechanism Arguments Seconds Integer or integer expression Exceptions instantiation_error The argument Seconds must not be a variable but a variable was specified type_error integer The argument Seconds must be an integer or an integer expression but is a term of another type
92. HOME prorc was given Consult file see consult 1 If the file file does not exist and if file does not have the suffix pro the suffix is appended and the name thus produced is used IF Prolog V5 3 9 Reference Manual Prolog system System command prolog 1 file Load file see load 1 If it does not exist and if file does not have the suffix cmp the suffix is appended and the name thus produced is used The system parameters c and 1 are processed in the order of their appearance in the command line The system parameters c and 1 are processed after the parameters r and st Independently of their position in the command line the following system parameters are evaluated before the parameters r st c and 1 sp search_path Set the initial value of the Prolog search_path flag to the list specified in search_path If more than one path name is given the pathnames are sepa rated by means of a system dependent character like the colon UNIX or the semicolon DOS msg number k K Set the initial size of the global stack to number bytes If k or K after number is given it is set to number kilobytes If required for program execution the memory area is automatically increased msc number k K Set the initial size of the constraint data stack to number bytes If k or K after number is given it is set to number kilobytes If required for program execution the memory area is automatically increased m
93. ISO standard for Prolog The directive init 1 is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also load 1 consult 1 reconsult 1 IF Prolog V5 3 307 Reference Manual Term classification Predicate integer 1 Test for integer integer TestTerm The predicate integer 1 succeeds if TestTerm is an integer otherwise it fails Arguments Test Term Term Hints If IF Prolog is configured with the extension rational numbers multiple precision inte gers may be used The predicate integer 1 succeeds for them too Example user integer 9 lt ENTER gt yes user integer X lt ENTER gt no user X is 5 2 integer X lt ENTER gt X 3 lt ENTER gt yes Standard This predicate complies with the definition of the ISO standard for Prolog See also atom 1 atomic 1 compound 1 cyclic 1 float 1 ground 1 nonvar 1 number 1 rational 1 var 1 Reference Manual 308 IF Prolog V5 3 is 2 Predicate Arithmetic Evaluate arithmetic expressions Result is Expression is Result Expression The predicate is 2 evaluates the arithmetic expression Expression and unifies the result with Result A call of is 2 can be compared to an assignment statement in other programming languages Functions are an important part of arithmetic expressions They are described in det
94. Massachusetts MIT Press 1986 835 Index abs 309 absolute value 309 access structure arguments 740 acos 309 add a complex C function 693 add a simple C function 694 addition 309 anonymous variable 806 appending lists 77 arc cosine 309 arc sine 309 arc tangent 309 argument precedence associativity 814 arithmetic expression 820 arithmetic function 309 820 arity 809 array create 171 dimension 83 query element 265 set element 477 array term test 82 ASCII character syntax 802 asin 309 associativity of an argument 814 atan 309 atom analyze 545 compose 103 concatenation 159 concatenation of atoms 341 convert to character code list 101 convert to character list 99 convert to number 107 836 decompose 103 113 generate 764 index 304 number of bytes 124 number of characters 105 parse 392 prefix 111 subatom 109 545 suffix 115 syntax 799 syntax analysis 392 test 97 749 unify 781 backslash 799 backtracking disable 39 initiate 243 binary number syntax 802 bitwise conjunction 309 bitwise disjunction 309 bitwise exclusive or 309 bitwise left shift 309 bitwise right shift 309 body of a module 121 Branch back to CALL port of parent goal 635 Branch back to CALL port of subgoal 636 Branch back to clause head 634 Breakpoint reactivate 632 buffer flush 736 byte input 266 395 output 428 C Function call on IF Prolog shutdown 695 Inde
95. Mod Pred Arity lt ENTER gt write Mod outtab 10 lt ENTER gt write Pred outtab 30 lt ENTER gt write Arity nl lt ENTER gt Pred system lt ENTER gt system 2 system 2 system calling_context 1 system catch 3 system is 2 system 2 system lt 2 system gt 2 system 2 system 2 system 2 system system 5 Mod system Pred system Arity 5 lt ENTER gt yes user write First line outtab 10 lt ENTER gt write Table stop nl lt ENTER gt First line Table stop yes Reference Manual 390 IF Prolog V5 3 outtab 1 2 Predicate Elementary input output Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also tab 1 2 write 1 2 IF Prolog V5 3 391 Reference Manual Term conversion Predicate parse_atom 6 Parse a character string in accordance with Prolog syntax parse_atom String StartPosition EndPosition Term VarList Error The predicate parse_atom 6 parses String in accordance with the Prolog syntax see section 9 Parsing starts at StartPosition and ends at the first period which cannot be part of the term syntax This may be e a period followed by a delimiter or e a period at the end of String If a correct term is recognized this term is unified with Term and Error is unified with 0 In addition VarLis
96. Module asserta_with_names Head Body VarList Module The predicate asserta_with_names 2 acts in the same way as asserta 1 but the infor mation in the list VarList on variables in the clause is also stored in the database The predicate asserta_with_names 3 acts in the same way as asserta 2 but the infor mation in the list VarList on variable in the clause is also stored in the database The list VarList contains information on the variables occurring in the clause and their names in the following format Name Variable Only the information relating to the clause is transferred to the database The information in VarList need not be complete Arguments Clause Structure atom Head Structure atom Body Term VarList List with format Name Variable Name Atom Variable Variable Exceptions instantiation_error The argument Head Clause or VarList must not be a variable but a variable was specified type_error callable The argument Head Body or Clause must have the syntactical structure of a Prolog goal permission_error modify static_procedure The argument Head or the head of Clause specifies an existing predicate which has not been declared as dynamic and therefore cannot be modified permission_error access calling_context The argument Body or the body of Clause contains a call involving calling_con text 1 in a predicate that is not a metapredicate type_error list The ar
97. Predicate system_hostid 1 Query machine identification system_hostid Hostid The predicate system_hostid 1 unifies Hostid with an integer representing a unique ma chine identification Arguments Hostid Integer Exceptions type_error integer The argument Hostid must be a variable or an integer but is a term of another type Hints This host identification varies from one computer to another and can be used in an application to control actions specific to the machine Example user system_hostid Hostid lt ENTER gt Hostid 1762018966 lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1A The predicate system_hostid 1 is new Reference Manual 558 IF Prolog V5 3 system_hostid 1 Predicate System information See also prolog_serial 1 prolog_version 1 proroot 1 system_name 1 IF Prolog V5 3 559 Reference Manual System information Predicate system_name 1 Query operating system system_name SystemName The predicate system_name 1 unifies SystemName with an atom containing the name of the operating system Arguments SystemName Atom Exceptions type_error atom The argument SystemName must be a variable or an atom but is a term of another type Hints This name varies from one operating system to anot
98. PredicateList must be a regular list but is a term of another type or not regular type_error predicate_indicator The argument Predicate in PredicateList must be a predicate indicator i e a structure with the format Functor Arity but is a term of another type type_error atom The name of the predicate Predicate in PredicateList must be an atom type_error integer The arity of the predicate Predicate in PredicateList must be an integer domain_error not_less_then_zero The arity of the predicate Predicate in PredicateList must be a positive integer but is negative representation_error max_arity The arity of the predicate Predicate in PredicateList must be an integer in the range 0 127 but is larger permission_error modify procedure The predicate indicator Predicate in PredicateList specifies a predicate which al ready exists and is not modifiable or which is the name of a language construct permission_error directive module The specified directive meta 1 is not valid in this position Hints The atom meta is defined as a prefix operator Directives are evaluated during consultation see consult 1 reconsult 1 or compi lation see compile 1 procmp command Standard The directive meta 1 is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also module 1 begin module 1 end_module 0 1 import 1 2 export 1 reexport 1 2 privat
99. Prolog user listing lt ENTER gt h user my_system 1 my_system Com unix_fork Pid exec_father_son Pid Com user exec_father_son 2 exec_father_son 0 Com l exec Com exec_father_son Pid _ repeat unix_wait Pid yes user my_system 1ls 1 pro lt ENTER gt Irw Iw 1 bre prolog 11 Jul 14 09 46 example pro yes See also the example in the section Process management and communication in the IF Prolog User s Guide 2 Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also unix _fork 1 unix_wait 1 2 unix_kill 2 system 0 1 2 3 5 IF Prolog V5 3 239 Reference Manual Database Predicate expand_term 2 Transform a grammar rule expand_term TermIn TermOut The predicate expand_term 2 transforms a grammar rule into a normal Prolog term The predicate is used by the language construct gt 2 If TermIn has not the structure of a grammar rule TermOut is unified with the unexpanded Termin Arguments TermIn Term TermOut Term Example user expand_term a gt r1 r2 T T a _214 _213 r1 _214 _213 r2 _214 _213 lt ENTER gt yes user expand_term sentence gt nom_phrase verb_phrase T T sentence _214 _213 nom_phrase _214 _230 verb_phrase _230 _213 yes Standard
100. Prolog flag iso Compatibility V5 1A The predicate list_last 2 is new See also member 2 memberchk 2 nonmember 2 list nth 3 Reference Manual 318 IF Prolog V5 3 list_length 2 Predicate List processing Count the elements in a list list_length List Length The predicate list_length 2 unifies Length with the number of elements in the list List Arguments List List Length Integer Exceptions instantiation_error The argument List must not be a variable but a variable was specified type_error list The argument List must be a list but is a term of another type type_error integer The argument Length must be a variable or an integer but is a term of another type domain_error not_less_than_zero The argument Length must be a positive integer but is negative Example user list_length nt tp brc L lt ENTER gt L 3 lt ENTER gt yes user list_length L lt ENTER gt L 0 lt ENTER gt yes Standard This predicate complies with the definition of the ISO standard for Prolog IF Prolog V5 3 319 Reference Manual List processing Predicate list_length 2 See also atom_length 2 Reference Manual 320 IF Prolog V5 3 list_mode 3 Predicate Database Query and set the list mode of a predicate list_mode Predicate Before After Module The predicate list_mode 3 determines whether or not the predicate Predicate may be
101. Prolog flags known in IF Prolog and Value with its current value Prolog flags are used to make global settings for IF Prolog The following tables contain the available Prolog flags and their permissible values default values printed in boldface The following Prolog flags may be queried and modified Flag Value Description consult notify A message is output when a Prolog text is loaded nonotify No message is output when a Prolog text is loaded search_path Paths If input files are not specified using a complete path name they are searched for in the directories speci fied in the Paths list The default value of this Pro log flag is the value of the system parameter sp if specified otherwise it is the value of the environment variable PROPATH or it is empty read_error error Syntax errors found by analysis with read_term 2 3 etc raise an exception fail Syntax errors found by analysis with read_term 2 3 etc are reported directly by the parser in a message and the predicate fails quiet Syntax errors found by analysis with read_term 2 3 etc are not reported and the predicate fails report_read_error on Syntax errors found by analysis with parse_atom 6 are reported directly by the parser in a message off Syntax errors found by analysis with parse_atom 6 are not reported by the parser but can be queried with the read_error 2 3 predicates warnings on For consult 1 etc warnings are output for possible errors
102. PrologError t_cursor ActGoal TERM Term The function PrologError returns TRUE when an error has occurred during the execution of the goal ActGoal with PrologFetch An error has occurred when during the execution of ActGoal a context jump e g implicitly triggered by an exception is initiated and no matching context can be found The term pointed at by Term is set to the error term see throw 1 which contains infor mation about the error Arguments ActGoal Structure information on the current Prolog goal Term Pointer to term variable Hints When an error has occurred during the execution of ActGoal the next activation of ActGoal with PrologFetch will restart the execution of the goal i e the first solution will then be found See also PrologClose PrologFetch PrologOpen IF Prolog V5 3 721 Reference Manual Passive C interface C Function PrologFetch Find solutions for a goal include cpro h BOOLEAN PrologFetch t_cursor ActGoal The function PrologFetch searches for a solution for the current Prolog goal ActGoal If a solution can be found PrologFetch returns TRUE Otherwise it returns FALSE When a solution has been found a subsequent call of PrologFetch will lead to the next solution e g backtracking takes place If no solution has been found or if an error did occur see PrologError a subsequent call of PrologFetch will restart the query and will th
103. The language construct fail 0 always fails so it can be used deliberately to initiate back tracking In the course of backtracking variable instantiations which have arisen during goal execution are undone at least up to a point in the search tree at which further solutions can be formed Hints For ANDed 2 subgoals subgoals to the right of a fail 0 subgoal are never executed If fail O is called after a predicate which succeeds any number of times in the course of backtracking e g repeat 0 an endless loop may result The language construct fail O is not a predicate so it cannot be redefined The predicates current_predicate 1 and current_visible 2 do not indicate language constructs Explicit module qualification with 2 or 2 is not permitted for language constructs with the exception of cal1 1 Example The predicate not 1 can be implemented by the following clauses with 0 and fail 0 user listing lt ENTER gt J user not_new 1 not_new Goal calling_context M call Goal M f fail not_new _ yes user not_new true lt ENTER gt no user not_new fail lt ENTER gt yes IF Prolog V5 3 243 Reference Manual Execution control Language construct fail 0 Loops can be formed with fail 0O and predicates which have several solutions user for 1 1 3 lt ENTER gt write 1I nl lt ENTER gt fail lt ENTER gt no Standard This language con
104. The name for internet domain socket must have the form Port where Port is the port number If Port is uninstantiated the system chooses a port and Port is unified with its number The name for unix domain socket must be an atom Filename The file thus created will be deleted when the socket is closed by socket_shutdown 1 2 Arguments Socket Socket system defined term Addr Integer Port or atom Filename Host Atom Port Integer Filename Atom Exceptions instantiation_error The argument Socket must not be a variable but a variable was specified type_error socket The argument Socket must be a socket supplied by socket 3 but is a term of another type domain_error socket The argument Socket must be a currently open socket supplied by socket 3 type_error integer The argument Port must be a variable or an integer but is a term of another type type_error atom The argument Filename must be an atom but is a term of another type domain_error file_name The value of the argument Filename is not a valid name for a file permission_error open source_sink The argument Filename specifies a file or a different I O medium that cannot be opened Hints This predicate is used normally in a server process The client process uses the predicate socket_connect 2 IF Prolog V5 3 513 Reference Manual Net communication Predicate socket __bind 2 Standard This predicate is not required by the ISO standard for Prolog
105. Therefore it is not available in ISO compatibility mode see Prolog flag iso See also socket 3 current_socket 3 current_host 1 host_addr 2 net_service 3 socket_accept 3 socket_close 1 socket_connect 2 socket_listen 1 2 socket_receive 2 3 socket_raw_receive 4 5 socket_send 2 3 socket_shutdown 1 2 Reference Manual 514 IF Prolog V5 3 socket_close 1 Predicate Net communication Close a socket socket_close Socket The predicate socket_close 1 causes to close shut down and dismiss completely the socket Socket Arguments Socket Socket system defined term Exceptions instantiation_error The argument Socket or How must not be a variable but a variable was specified type_error socket The argument Socket must be a socket supplied by socket 3 but is a term of another type domain_error socket The argument Socket must be a currently open socket supplied by socket 3 Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1B The predicates socket_close 1 are new See also socket 3 current_socket 3 socket_accept 3 socket_bind 2 socket_connect 2 socket_close 1 socket_listen 1 2 socket _receive 2 3 socket _raw_receive 4 5 socket_send 2 3 socket_shutdown 1 2 IF Prolog V5 3 515 Reference Manual Net communication Predicate socket_connect 2
106. This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also gt 2 phrase 2 Reference Manual 240 IF Prolog V5 3 export 1 Directive Module concept Export predicates export PredicateList export PredicateList The directive export 1 makes all the predicates specified in the PredicateList available for other modules They must be made visible there with import 1 2 The directive export 1 may only occur in the module interface Predicates declared with the directive export 1 are also implicitly declared with private 1 Arguments PredicateList List with the format Predicate or structure with the format Predicate Predicate Structure with the format Functor Arity Functor Atom Arity Integer 0 lt Arity lt 127 Exceptions Errors in directives are detected with consult 1 reconsult 1 or compile 1 No exceptions are generated Instead only error messages are output on the current error output stream This directive can produce the following error messages instantiation_error The argument PredicateList or a subterm must not be a variable but a variable was specified type_error list The argument PredicateList must be a regular list but is a term of another type or not regular type_error predicate_indicator The argument Predicate in PredicateList must be a predicate indicator i e a st
107. V5 3 is 2 Predicate Arithmetic Standard This predicate complies with the definition of the ISO standard for Prolog The functions acos 1 asin 1 cosh 1 sinh 1 tan 1 tanh 1 rdiv 2 signum 1 1 2 min 2 max 2 and all zero arity functions are not part of the ISO standard for Prolog In ISO compatibility mode see Prolog flag iso none of these functions can be used Compatibility V5 0A The functions random 0 signum 1 float_integer_part 1 float_frac tional_part 1 and rdiv 2 are new The result type of the function sign 1 has been changed incompatibly V5 0B ISO conformance exception type_error evaluable is generated instead of type_error number when the argument Expression is not a number or an evaluable arithmetic expression V5 1A The functions pi 0 2 min 2 and max 2 are new IF Prolog V5 3 315 Reference Manual Term classification Predicate letter 1 Test for letter letter TestTerm The predicate letter 1 succeeds if TestTerm is an atom which consists of one letter char acter otherwise it fails Which characters are letters depends on the national language environment variable LANG and on the current language current_language 1 Arguments Test Term Term Example user letter a lt ENTER gt yes user letter 7 lt ENTER gt no S gt lt Il user C letter X lt ENTER gt no user X C letter X lt ENTER gt
108. a Prolog file reconsult Filename Module Filename Module The predicate reconsult 1 reads the file Filename into the database in the calling module or in the specified Module To enable Prolog text to be entered interactively as well the atom user may also be specified for Filename In this case reconsult 1 reads from the current input stream and displays a gt gt prompt to indicate that a clause or a directive is expected and a prompt to indicate that a clause or a directive that has already begun has not yet been completed By entering end_of_file or pressing the appropriate key it is possible to terminate the consult process Clauses occurring in Filename are read in with read_term 2 checked for correct syntax and inserted with assertz 1 or assertz_with_names 2 into the database of the relevant module Clauses with syntax errors are not inserted into the database If there are already clauses in the database for a predicate defined in Filename they are deleted before the new clauses are inserted in the database If the Prolog flag debug is set to on assertz_with_names 2 is used for insertion in the database so that for example listing 0 1 can be used to display the clauses of these predicates with their original variable names Otherwise assertz 1 is used If grammar rules formulated with gt 2 occur in Filename they are interpreted by recon sult 1 and converted into normal Prol
109. a computer running under the UNIX DOS Windows and other operating system As the set of manuals for IF Prolog are not tutorials you should be familiar with the Prolog language You should also be familiar with the basics of the operating system and know how to use one of the editors installed on your computer Reference Manual 2 IF Prolog V5 3 Preface The following notational conventions are used throughout this manual XXX bind Name Et atom 1 nl 0 1 1 Syntax definitions are enclosed within a frame Prolog language elements operating system commands and outputs from the system are printed in teletype font Italics are used to represent variable parts in inputs and outputs where you should substitute them with your own values Square brackets denote optional entries in the syntax notation the brackets are not part of the Prolog text Square brackets in bold type are elements of the Prolog list notation and are part of the Prolog text Braces denote alternatives in the syntax notation the brackets are not part of the Prolog text A bar denotes alternatives in the syntax notation Parentheses are required parts of the Prolog predicate notation and is part of the Prolog text Ellipsis indicate that the preceding syntax element may be re peated Predicates are specified in the form Name Arity Several predicates with the same name and different arities are denoted in this f
110. a goal string and store the information include cpro h BOOLEAN ParseProlog STRING GoalAtom t_parse_context Context The function ParseProlog prepares the execution of a Prolog goal The character string String is parsed in accordance with the Prolog syntax see the section 9 on Prolog syntax Parsing ends at the first period which cannot be part of the term syntax The characters after the are not used If the parsing of the string was successful ParseProlog returns TRUE otherwise it returns FALSE The information about the goal is stored in the structure pointed at by Context The following structure components of Context are set when parsing is successful Component Meaning Context gt pc_term Prolog term Context gt pc_varlist List of Prolog variables Context gt pc_position Position after the end Context gt pc_errno 0 The following structure components of Context are set when a syntax error is determined Component Meaning Context gt pc_position Position of the syntax error Context gt pc_errno Syntax error number Arguments GoalAtom Character string Context Pointer to structure where information about the Prolog goal is stored Hints The parsed Prolog goal can be processed by PrologOpen or QueryCreate IF Prolog V5 3 713 Reference Manual Passive C interface C Function ParseProlog See also PrologOpen QueryCreate ParseError parse_atom 6 Reference Manua
111. a variable was specified type_error socket The argument Socket must be a socket supplied by socket 3 but is a term of another type domain_error socket The argument Socket must be a currently open socket supplied by socket 3 type_error integer The argument How must be an integer but is a term of another type domain_error how The argument How is not in the prescribed range of values Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso IF Prolog V5 3 525 Reference Manual Net communication Predicate socket_shutdown 1 2 See also socket 3 current _socket 3 socket_accept 3 socket_bind 2 socket _close 1 socket_connect 2 socket_listen 1 2 socket_receive 2 3 socket_raw_receive 4 5 socket _send 2 3 Reference Manual 526 IF Prolog V5 3 sort 2 Predicate List processing Sort a list sort List SortedList The predicate sort 2 constructs a sorted list from the elements in List and unifies the new list with SortedList The collating sequence is determined by the order of terms in Prolog see lt 2 and is in ascending order If there are multiple occurrences of elements in List each such element will appear only once in the sorted list Arguments List List SortedList List Exceptions instantiation_error The argument List must not be a variable but a variable was
112. aa areas current_signal 2 Query signals and modes oaoa a a a current_socket 3 Query communication sockets current_stream_control 3 Query information on device drivers current_visible 2 Query visible predicates gyclic 1 Test for cyclic termi o es aomi tod wee wwe oe ee eed debug 1 Activate the debugger foragoal 0 debug_begin 0 User defined debugger initialization debug_config 3 Configure the debugger debug_end 0O User defined termination of the debugger debug_mode 3 Query and set the debug mode of a predicate default_editor 2 Query and set the editor device_control 2 Control an input output device digit 1 Test Tor digit ace kG AB e oe Se BG RB Be Bre discontiguous 1 Declare discontiguous predicate definition dynamic 1 Declare predicates as modifiable 0 vi edit O L Edita mile ee goa ae amp oe oe we RO Be ee Ae Od we 223 end_module 0 1 Conclude the definition of a module 225 ensure_loaded 1 Insert a Prolog file in the source text once 227 error_tell 1 Set current error output stream 229 error_telling 1 Query current error output stream 231 error_told 0O Reset current error output stream 232 Sexcepliony2 Raise a exception nw
113. addressed via the built in alias current_ error as well Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also error_tell 1 error _telling 1 current error 2 set_error 1 close 1 2 Reference Manual 232 IF Prolog V5 3 exception 2 Predicate Contexts Exceptions Raise an exception exception Error Info The predicate exception 2 raises an exception explicitly Each exception is defined by two criteria 1 Type of error Error Error is a term from the following set evaluation_error Problem An arithmetic expression could not be evaluated without error domain_error ValidDomain ErrorTerm The argument type is correct but the argument does not lie within the pre defined value range existence_error Object ErrorTerm An object involved in an operation is not available instantiation_error An argument or subterm of an argument is a variable permission_error Operation Object ErrorTerm Execution of an operation on an object is not permitted representation_error Flag ErrorTerm An implementation related restriction was exceeded resource_error Resource IF Prolog does not have sufficient resources available to continue with pro cessing syntax_error A character string which is to be read as a term does not observe Prolog syntax system_error An error involving the operating syste
114. an atom but is a term of another type domain_error prolog_flag The value of the argument Flag is not a valid Prolog flag domain_error flag_value The value of the argument Value is none of the values valid for a Prolog flag permission_error modify flag The argument Flag is the name of a Prolog flag the value of which may not be modified Standard The directive set_prolog_flag 2 complies with the definition of the ISO standard for Prolog The Prolog flags backtrace consult double_quotes extended_syntax float_max float_min iso nested_comments notty prompt read_error report_read_error search_path signal warnings and write_depth are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso IF Prolog V5 3 493 Reference Manual System information Directive set_prolog_flag 2 See also current _prolog flag 2 Reference Manual 494 IF Prolog V5 3 set_socket_option 3 Predicate Net communication Set socket option set_socket_option Socket Option Value The predicate set_socket_option 3 sets an option for a communications socket The argument Socket must be a term representing a socket The set of supported options and corresponding values is system dependent The following table contains the allowed values for Option The predicate set_socket_option 3 succeeds even if the given option Option is not supported
115. application itself Example The file example pro contains the following application program test program write ende nl test write test nl fail If this file is loaded on invoking IF Prolog the application will be executed immediately prolog nonotify c example pro lt ENTER gt IF PROLOG V5 1 Copyright C Siemens Nixdorf Information Systems AG 1996 test ende Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Reference Manual 420 IF Prolog V5 3 program 0 User definable predicate Execution control See also break 0 system_parameters 1 IF Prolog V5 3 421 Reference Manual System information Predicate program_parameters 1 Query parameters from IF Prolog call program_parameters ParameterList The predicate program_parameters 1 unifies ParameterList with a list of all parameters which were specified on calling IF Prolog The first element of the list is the name under which IF Prolog was called Arguments ParameterList List of atoms Exceptions type_error list The argument ParameterList must be a variable or a list but is a term of another type type_error atom An element of ParameterList must be a variable or an atom but is a term of another type Hints The first element of ParameterList need not match the name given by the user on the
116. as if the signal had never arrived provided passive signal handling mode off has been activated for Signal The predicate signal_control 2 is always successful with this Command received The predicate signal_control 2 succeeds if passive signal handling mode off has been activated for Signal and the arrival of Signal was registered i e the counter for this Signal has a value greater than 0 The counter for the arrival of Signal is decremented by 1 Otherwise the predicate fails received Name The predicate signal_control 2 succeeds if passive signal handling mode off has been activated for Signal and the arrival of Signal was registered Reference Manual 502 IF Prolog V5 3 signal_control 2 Predicate Contexts Exceptions i e the counter for this Signal has a value greater than 0 The counter for the arrival of Signal is decremented by 1 Otherwise the predicate fails The argument Name is then unified with the name of the signal received This is useful if all is specified for Signal since Name is then unified with the actual signal name Arguments Signal Atom all abort alarm interrupt pipe quit termination user_1 user_2 Command Atom or structure on off default ignore clear received received Name Exceptions instantiation_error The argument Signal or Command must not be a variable but a variable was specified type_error atom The argument Signal must be an atom but is a term
117. backtracking is initiated i e the predicate is evalu ated with fail warning If a predicate is to be activated which is not defined a warning is output and backtracking is initiated i e this predicate is evaluated with fail The warning is not output for predicates for which the exception mode has been set to on see predicate_mode 3 debug on For consult 1 and reconsult 1 all predicates are implicitly declared as dynamic see dynamic 1 to support program testing off For consult 1 and reconsult 1 all the predicates which were not explicitly declared with dynamic 1 are declared as static These cannot then be modi fied tested or displayed prompt on Output of the prompt in the Prolog input loop and interaction for backtracking for goals which have been successfully executed in the Prolog input loop and for which variables have been instantiated always take place i e even if the standard input and the standard output are not terminals off Output of the prompt in the Prolog input loop and interaction for backtracking for goals which have been successfully executed in the Prolog input loop and for which variables have been instantiated take place only if the standard input and the standard output are terminals char_conversion on The character conversions defined with the predicate char_conversion 2 are performed when terms are read off No character conversion is performed when terms are read IF Prolog V5 3 489
118. be a variable but is a term of another type Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1B The predicate select 5 is new See also alarm 1 socket 3 current_socket 3 socket_accept 3 socket_bind 2 socket_connect 2 socket_close 1 socket_listen 1 2 socket_receive 2 3 socket_raw_receive 4 5 Reference Manual 476 IF Prolog V5 3 set_array 3 Predicate Term classification Set array element set_array Array Index Term The predicate set_array 3 sets the element of Array whose index is Index to Term The old value of the element is overwritten by the new value The element will be reset to the old value on backtracking Arguments Array Array system defined term Index Positive integer Term Term Exceptions instantiation_error The argument Array or Index must not be a variable but a variable was specified type_error array The argument Array must be an array but is a term of another type type_error integer The argument Index must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer domain_error array_size The argument Index must be a positive integer less than or equal to the number of elements in the array but is not positive or larger Furthermore if an arithmetic expre
119. be an atom but is a term of another type type_error atom The argument Value must be a variable or an atom but is a term of another type Hints The Prolog system uses the following environment variables Variable Used for TMPDIR directory for temporary files LANG national character set supported by the Prolog scanner TERM type of the terminal HOME name of HOME Directory of the user SHELL name of shell see system 0 EDITOR name of standard editor see edit 0 1 PROROOT path where Prolog is installed PRORC name of startup file PROHELP name of files with help information see help 0 1 PROPATH search path for files used by the Prolog system The predicate getenv 2 is based on the C function getenv 3C see 10 IF Prolog V5 3 287 Reference Manual Operating system Predicate getenv 2 Example The environment variable TERM indicates the type of data display terminal on which the current IF Prolog process is running e g user getenv TERM S lt ENTER gt S xterm lt ENTER gt yes user getenv pipapo X lt ENTER gt no Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also system 0 default_editor 2 system_parameters 1 Reference Manual 288 IF Prolog V5 3 ground 1 Predicate Term classification Test for ground instantiation ground TestTerm
120. be an integer in the range 0 127 but is larger permission_error modify procedure The predicate indicator Predicate specifies a predicate which already exists and is not modifiable or which is the name of a language construct type_error atom The argument After must be an atom but is a term of another type domain_error on_or_off The argument After must be one of the atoms on or off but is another atom type_error atom The argument Before must be a variable or an atom but is a term of another type domain_error on_or_off The argument Before must be a variable or one of the atoms on or off but is another atom permission_error access system_module The predicate debug_mode 3 must not be executed for a system module Hints The predicate debug_mode 3 is a metapredicate and manipulates the database in the calling module or in the specified Module A predicate may have certain attributes which when it is created are set implicitly by the system according to the current environment or declarations They can be modified to a certain extent explicitly by the user These include the following List mode see list_mode 3 Debug mode see debug_mode 3 Exception mode see predicate_mode 3 e Modification mode see modify_mode 3 These attributes are retained even if the predicate is deleted with abolish 1 for ex ample This predicate is not part of the IF Prolog runtime system and is therefore not available fo
121. be queried or modified At the time of the call Old is unified with the previous value of the trace parameter and then if unification was successful the new value New is set The following tracer parameters are available default values are printed in boldface Parameter Value Description call on The tracer logs every pass through this port or calls the user defined predicate trace_output 4 off The tracer does not log passes through this port exit on off the same applies to the EXIT port redo on off the same applies to the REDO port fail on off the same applies to the FAIL port error on off the same applies to the ERROR port wakeup on off the same applies to the WAKEUP port suspend on off the same applies to the SUSPEND port trymatch on off the same applies to the TRYMATCH port failmatch on off the same applies to the FAILMATCH port enterbody on off the same applies to the ENTERBODY port exitbody on off the same applies to the EXITBODY port redobody on off the same applies to the REDOBODY port failbody on off the same applies to the FAILBODY port display_depth 7 The maximum structure depth is restricted by this param eter when terms are output by the tracer If 0 is specified there is no restriction trace_length 100 Number of trace outputs to be stored if the alpha interface is being used Arguments Parameter Atom see table above Old Term context dependent New Term context dependent Reference Manual 576 IF Prolog V5
122. call enterbody fail failbody failmatch redo redobody suspend trymatch wakeup exit exitbody error all in ner outer c eb f fb fm Ir rb s tm w x xb er Switch Atom on off IF Prolog V5 3 649 Reference Manual Command interface Debugger command port 2 Exceptions instantiation_error The argument Ports or Switch or a subterm must not be a variable but a variable was specified type_error atom_or_list The argument Ports must be an atom or a list of atoms but is a term of another type domain_error port The argument Ports is not valid for a port of the box model type_error atom The argument Switch must be an atom but is a term of another type domain_error on_or_off The argument Switch must be one of the atoms on or off but is another atom domain_error arity The command port 2 was called with an incorrect number of parameters See also trace_port 2 Reference Manual 650 IF Prolog V5 3 remove_stop 0 1 Debugger command Command interface Remove explicit breakpoints remove_stop rs remove_stop Numbers rs Numbers The remove_stop 1 command removes the breakpoints specified using the Numbers argu ment If Numbers is omitted all current breakpoints are removed An integer or list of integers may be specified as the argument If a list is specified all the breakpoints included in the list are removed If the breakpo
123. can occur Standard These predicates comply with the definition of the ISO standard for Prolog The use of arithmetic expressions in the argument ExitStatus is not allowed in the ISO standard for Prolog In the ISO compatibility mode see Prolog flag iso therefore no arithmetic expressions may be used as arguments for this predicate Instead an evaluation must be programmed explicitly with the help of is 2 if necessary Reference Manual 290 IF Prolog V5 3 help 0 1 Predicate System information Display help information help help Pattern The predicate help 1 displays suitable help information for the specified Pattern if such information is available The argument Pattern can be specified as for match 2 3 and in most cases will be the name of a predicate The predicate help 0O provides help on help 1 Arguments Pattern Atom Exceptions instantiation_error The argument Pattern must not be a variable but a variable was specified type_error atom The argument Pattern must be an atom but is a term of another type permission_error open source_sink The file containing the help information cannot be opened Hints Search for help information takes place in the files defined by the environment variable PROHELP If the environment variable PROHELP does not exist the file prolib system hlp under the IF Prolog root directory see proroot 1 will be used Help information on all the b
124. character atom and the terminating period user parse_atom 1 P T V E lt ENTER gt P 5 T V E 0 lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also read_error 2 syntax_error 2 set prolog flag 2 current_prolog_flag 2 atom_length 2 Reference Manual 394 IF Prolog V5 3 peek_byte 1 2 Predicate Elementary input output Input a byte peek_byte ByteCode peek_byte Stream ByteCode The predicate peek_byte 1 peeks at the next byte from the current input stream cur rent_input and unifies ByteCode with its integer value The predicate peek_byte 2 acts in the same way for the specified input stream Stream If the end of the input stream has been reached ByteCode is unified with 1 The predicates can be applied only for binary streams see open 3 4 Arguments Stream Stream system defined term or alias atom ByteCode Integer 1 lt ByteCode lt 255 Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Strea
125. command line it may also be an appropriately expanded pathname under which IF Prolog was found in the system This name will usually vary from system to system Example The file example pro contains the following Prolog program program program_parameters List write List nl Calling IF Prolog as shown below would then return prolog nonotify c example data hello lt ENTER gt IF PROLOG V5 1 Copyright C Siemens Nixdorf Information Systems AG 1996 prolog nonotify c example data hello Reference Manual 422 IF Prolog V5 3 program_parameters 1 Predicate System information Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also system_parameters 1 user_parameters 1 IF Prolog V5 3 423 Reference Manual System information Predicate prolog_serial 1 Query IF Prolog serial number prolog_serial Serial The predicate prolog_serial 1 unifies Serial with an atom which contains the serial number of IF Prolog The serial number varies from one operating system to another and changes with each new release of IF Prolog It can be used to control system and version specific actions in an application Arguments Serial Atom Exceptions type_error atom The argument Serial must be a variable or an atom but is a term of another type Example user prolog_seri
126. compatibility mode see Prolog flag iso Compatibility V5 1A The predicate array 1 is new See also array 2 create_array 2 get_array 3 set_array 3 Reference Manual 82 IF Prolog V5 3 array 2 Predicate Term classification Query dimension of an array array Array Dimension The predicate array 2 queries the dimension of Array and unifies it with Dimension Arguments Array Array system defined term Dimension Integer Exceptions instantiation_error The argument Array must not be a variable but a variable was specified type_error array The argument Array must be an array but is a term of another type type_error integer The argument Index must be a variable or an integer but is a term of another type Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1A The predicate array 2 is new See also array 1 create_array 2 get_array 3 set_array 3 IF Prolog V5 3 83 Reference Manual Database Predicate asserta 1 2 Insert a clause in the database asserta Clause Module asserta Head Body Module The predicate asserta 1 inserts the specified Clause in the database in the calling module or in the specified Module as the new first clause of the associated predicate If the database does not contain the predicate in the
127. connected state before any data may be sent or received on it see socket_accept 3 and socket_connect 2 The argument Socket must be an uninstantiated variable It will be instantiated to a system generated term Arguments Domain Atom internet unix Type Atom datagram stream Socket Socket system defined term Exceptions instantiation_error The argument Domain or Type must not be a variable but a variable was specified type_error atom The argument Domain or Type must be an atom but is a term of another type domain_error socket_domain The argument Domain does not specify a valid domain for a socket domain_error socket_type The argument Type does not specify a valid type for a socket type_error variable The argument Socket must be a variable but is a term of another type Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso IF Prolog V5 3 509 Reference Manual Net communication Predicate socket 3 See also net_service 3 current_socket 3 socket_accept 3 socket_bind 2 socket_close 1 socket_connect 2 socket_listen 1 2 socket_receive 2 3 socket_raw_receive 4 5 socket _send 2 3 socket_shutdown 1 2 Reference Manual 510 IF Prolog V5 3 socket_accept 3 Predicate Net communication Accept a connection socket_accept Socket Addr NewSocket The predicate socket_accep
128. construct lists The term Term is appended to a list This function unifies the term Tail with a list whose head is the term Term and tail is a variable If unification is successful Tail is supplied with the new list tail and the function returns TRUE Otherwise the function returns FALSE Arguments Tail Pointer to term variable Term Term variable Example The following simple C function realizes a predicate make_list 2 which builds a list of five subsequent integers starting with the number given by the first argument include cpred h BOOLEAN make_list_2 void make_list Start List TERM list tail long start i if TermIsInteger PrologArg 1 amp start return FALSE list TermOpenList amp tail for i 0 i lt 5 i TermAddList amp tail TermMakeInteger startti TermCloseList tail return TermUnify PrologArg 2 list Reference Manual 738 IF Prolog V5 3 TermAddList C Function Active C interface void Cboot void CPRIM make_list 2 make_list_2 See also TermOpenList TermCloseList IF Prolog V5 3 739 Reference Manual Active C interface C Function TermArg Access structure arguments include cpred h TERM TermArg ARITY Argno TERM Term The function TermArg returns the Argnoth argument of the structure Term If Term is not a structure or Argno is not within the valid range of values IF Prolog is exite
129. course of backtracking Intermediate results obtained from a loop programmed with repeat 0 are thus lost with each backtracking cycle When subgoals are combined with AND 2 subgoals to the left of a repeat 0 subgoal are never reached again by backtracking If a predicate which always fails e g fail 0 is called after repeat 0 it may create an endless loop Loops created with repeat 0 should always be terminated with a cut 0 to prevent the loop from being traversed again after the end of loop criterion has been reached Example The following example reads terms and pushes them onto a stack user repeat lt ENTER gt read Term lt ENTER gt push_global stack Term lt ENTER gt Term end lt ENTER gt lineil lt ENTER gt line2 lt ENTER gt end lt ENTER gt Term end lt ENTER gt yes The following loop pops all terms from the stack and outputs them user repeat lt ENTER gt pop_global stack Term lt ENTER gt write Term nl lt ENTER gt Reference Manual 456 IF Prolog V5 3 repeat 0 Predicate Execution control not current_global stack lt ENTER gt end line2 linel Term line1 lt ENTER gt yes Standard This predicate complies with the definition of the ISO standard for Prolog See also 0 fail 0 true 0 for 3 IF Prolog V5 3 457 Reference Manual Stream processing Predicate reset __streams 0 Restore default values for current streams
130. depth of a structure reduce Level Term ReducedTerm The predicate reduce 3 converts Term to a term with a maximum structure depth of Level and unifies the result with ReducedTerm Arguments Level Integer or integer expression Term Term ReducedTerm Term Exceptions instantiation_error The argument Level must not be a variable but a variable was specified type_error integer The argument Level must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer Furthermore if an arithmetic expression is specified for the argument Level all the exceptions for is 2 can occur Example user reduce 1 a b c y c yy d T lt ENTER gt T a 2 lt ENTER gt yes user reduce 3 a b c y c yy d T lt ENTER gt T a b c 1 c 1 d lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso IF Prolog V5 3 449 Reference Manual Module concept Directive reexport 1 2 Reexport predicates reexport Module reexport Module reexport PredicateList from Module reexport Module PredicateList The directive reexport 1 makes all the predicates exported reexported from the module Module available for other modules The directive reexport 2 makes all the predicates specifi
131. equivalent to abcdef In all other cases the syntax violation illegal escape sequence is reported Examples of atoms anna m5 has_account_number append 21 Nomen est omen Don t forget that single quotes must be duplicated It s also possible to escape them n line feed before new text 7 gt lt x The length of an atom number of characters may be queried with the predicate atom_ length 2 Numbers Numbers in Prolog may be either binary octal decimal hexadecimal integers rationals or floating point numbers Integers are sequences of binary octal decimal hexadecimal digits optionally preceded by a minus sign An ASCII character preceded by the prefix Zero quote 0 denotes an integer which represents its ASCII code sequence of digits Ox hexadecimal sequence 0o octal sequence 0b binary sequence 0 ASCII character IF Prolog V5 3 801 Reference Manual Prolog Syntax Terms Sequence of digits Sequence of digits 0 9 Hexadecimal sequence sequence of hexadecimal characters 0 9 a f A F Octal sequence Sequence of octal characters 0 7 Binary sequence Sequence of binary characters 0 1 ASCII character a single character see Atoms The full machine word range 32 or 64 bits is available for integer arithmetic The following app
132. flag iso See also see 1 seen 0 set_input 1 current_input 1 error_telling 1 telling 1 IF Prolog V5 3 473 Reference Manual Stream processing Predicate seen 0 Reset current input stream seen The predicate seen O resets the default input stream user_input as the current input stream If the earlier current input stream was not a default stream it is closed see close 1 Hints All input predicates that have no explicit stream argument refer to the current input stream This stream can always be addressed via the built in alias current_input as well Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also see 1 seeing 1 current_input 1 set_input 1 close 1 2 Reference Manual 474 IF Prolog V5 3 select 3 4 5 Predicate Net communication Synchronous input multiplexing select Streams Timeout ReadyReadStreams select Streams Timeout ReadyReadStreams ReadyWriteStreams select SocksOrStreams Timeout ReadyReadSOS ReadyWrite SOS Timeleft The predicate select 3 examines the streams in the list Streams for readable data Each element of Streams must be a stream opened for reading The predicate select 4 examines the streams in the list Streams for readable or writable data Each stream element of SocksOrStreams must be either a sock
133. for goals which have been successfully executed in the Prolog input loop and for which variables have been instantiated take place only if the standard input and the standard output are terminals char_conversion on The character conversions defined with the predicate char_conversion 2 are performed when terms are read off No character conversion is performed when terms are read Reference Manual 192 IF Prolog V5 3 current _prolog_flag 2 Predicate System information backtrace 10 The maximal length of the backtrace list The list is created when an exception has been raised and con tains the calling sequence of goals that has led to the exception The elements of the list are predicate in dicators Functor Arity Goals that have been re moved due to tail recursion optimization normally the last subgoal in a clause body are not included in the list double_quotes codes Characters inside double quotes are to be inter preted as a list of character codes when reading a term e g with read 1 2 chars Characters inside double quotes are to be inter preted as a list of characters when reading a term e g with read 1 2 atom Characters inside double quotes are to be inter preted as an atom when reading a term e g with read 1 2 extended_syntax on Cyclic terms can be entered using the notation Variable Term When reading such a cyclic term Variable is unified with Term The above notation i
134. from IF Prolog call 422 prolog_serial 1 Query IF Prolog serial number 424 prolog_version 1 Query IF Prolog version 425 proroot 1 Query path of IF Prolog system 45 426 push_global 2 Set value of a global variable 427 put byte 1 2 Outpt a byte 2 sies s e sie arg ee Se eee Ee i 428 p t char 1 2 Output acharacter gt s sers ie ene ee ee a Re a i 430 p t code 1 2 Output a Characters s aa ioes e ee ee Ree 432 rational 1 Test for rational mumiber o cosce i Doe ba Soe be a eS 434 rational 3 Decompose a rational number 435 ad 1 2 Inp t tet a eee we RE RDS RE Re A Re R a a 437 read_error 2 3 Query position of a syntax error 440 read_term 2 3 Input a term 2 eek ee we hae bebe w ee HH R BD 442 reconsult 1 Read ina Prolog file 0 4 446 reduce 3 Reduce the depth of a structure 449 reexport 1 2 Reexport predicates 000 00 0000 450 regexp 2 3 Match a regular expression 00 452 remove 3 Remove asublist froma list 0 0 454 repeat 0 Generate a choice point 000 0000 456 reset_streams 0 Restore default values for current streams 458 retract 1 2 Remove a clause from database 459 retract_with_names 2 3 Remove a clause from database 461 reverse 2
135. goal 205 IF Prolog V5 3 837 Reference Manual Index debugger configure 208 initialize 207 termination 211 declaration of predicates 413 decomposing a list 77 delimiters 794 in expressions 796 in structures 796 device driver register 696 digit test 218 dimension array 83 directive begin_module 121 char_conversion 136 discontiguous 219 dynamic 221 end_module 225 ensure_loaded 227 export 241 import 299 include 302 init 306 initialize 306 meta 349 module 354 multifile 358 nonotify 366 op 383 private 413 reexport 450 set_prolog_flag 493 directory change current 138 check access permission 245 check existence 245 query current 285 disabling the return key 797 disjunction 309 Display breakpoints 679 Display constraints 674 Display default values 673 Display fields select 671 Display help information 647 Display history 678 Display list of predicates in module 675 Display listing of a predicate 676 Display variable constraints 680 division 309 division remainder 309 dsize 309 dused 309 editor call 223 query 215 set 215 element array 265 477 individual list element 324 last list element 317 list membership 344 347 364 of a list 812 empty list generate 773 test 760 unify 789 end of file query 95 end of line query 93 end of stream query 95 end of line comments 796 environment change drive 599 file information 273
136. halt si si as as ds ds rs rs st st si si si si OP ca Set interactive breakpoint Set interactive breakpoint to the monitoring of variables Reactivate current breakpoints Reactivate breakpoints Deactivate all breakpoints temporarily Deactivate breakpoint temporarily Remove all current explicit breakpoints Remove explicit breakpoints Set breakpoint Set breakpoint to the monitoring of variables Set interactive breakpoint Set interactive breakpoint Set interactive breakpoint Set interactive breakpoint to the monitoring of variables Functionality Terminate interactive debugger Start new input loop Execute a Prolog goal Terminate debugger and IF Prolog Interrupt interactive debugger and start the shell Terminate interactive debugger Start new input loop Execute a Prolog goal Terminate debugger and IF Prolog Reference Manual 624 IF Prolog V5 3 Debugger commands Overview by functionality system S Configuration Command Short port Ports Switch p Interrupt interactive debugger and start the shell Functionality Set debugger ports set_debug_depth Depth sdd Set structure depth set_history Number sh Configure history set_trace_depth Depth std Set structure depth for trace outputs set_trace_length Length stl Set length of trace field trace Switch td Sw
137. implemented by the complex C function Function A complex function is re executable i e allows backtracking Size specifies the size in bytes of the data structure needed for built in backtracking The predicate is assigned to the module user Arguments Functor Character string Arity Integer 0 lt Arity lt 127 Function C Function Size Integer Hints The function CPRED should be called from the C function Cboot which is executed at startup of IF Prolog See also Cboot CPRIM MCPRIM MCPRED IF Prolog V5 3 693 Reference Manual Active C interface C Function CPRIM Add a simple C function to IF Prolog include cpred h void CPRIM STRING Functor ARITY Arity CPRIMFUN Function The function CPRIM is used to incorporate the predicate Functor Arity into IF Prolog The predicate is implemented by the simple C function Function A simple function is deterministic i e does not allow backtracking The predicate is assigned to the module user Arguments Functor Character string Arity Integer 0 lt Arity lt 127 Function C Function Hints The function CPRIM should be called from the C function Cboot which is executed at startup of IF Prolog See also Cboot CPRED MCPRIM MCPRED Reference Manual 694 IF Prolog V5 3 Cshutdown C Function Active C interface Call a C function on IF Prolog shutdown include cpred h void
138. in the calling module or in the specified Module Standard Only the predicate retract 1 complies with the definition of the ISO standard for Prolog See also abolish 1 asserta 1 2 assertz 1 2 clause 2 retract _with_names 2 3 modify_mode 3 Reference Manual 460 IF Prolog V5 3 retract_with_names 2 3 Predicate Database Remove a clause from database retract_with_names Clause VarList Module retract_with_names Head Body VarList Module The predicates retract_with_names 2 3 act in the same way as retract 1 2 except that any name information on variables is also unified with VarList in the form Name Variable If there is no such information VarList is unified with the empty list The predicates retract_with_names 2 3 succeed by backtracking for all matching clauses which were found in the database at the time of the first call even if they have since been modified logic update view Arguments Clause Structure atom Head Structure atom Body Term VarList List in the form Name Variable Name Atom Variable Variable Exceptions instantiation_error The argument Head or Clause must not be a variable but a variable was specified type_error callable The argument Head or the head of Clause must have the syntactical structure of a clause head permission_error modify static_procedure The argument Head or the head of Clause specifies an existing pr
139. input output stream supplied by open 3 4 or Reference Manual 614 IF Prolog V5 3 write_term 2 3 Predicate Input output for terms an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error output stream The argument Stream is not a stream which has been opened for output open mode write or append system_error write system_error close system_error flush_output system_error interrupted The indicated error was reported by the operating system when writing on the output stream Stream instantiation_error The argument Options or a subterm must not be a variable but a variable was specified type_error list The argument Options must be a list but is a term of another type domain_error write_option An element of Options specifies an option that is not permitted Example user write_term lt ENTER gt struc f g one two lt ENTER gt maxdepth 1 nl lt ENTER gt struc f one yes user write_term lt ENTER gt struc f g one two lt ENTER gt maxdepth 1 stop etc nl lt ENTER gt struc f stop one etc yes user write_term new nline nl lt ENTER gt new line yes user write_term new nline lt ENTER gt IF Prolog V5 3 615 Reference Manual Inpu
140. input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream type_error atom The argument Command must be a variable or an atom but is a term of another type type_error integer The argument Arity must be a variable or an integer but is a term of another type domain_error not_less_than_zero The argument Arity must be a positive integer but is negative Reference Manual 200 IF Prolog V5 3 current _stream_control 3 Predicate Stream processing Hints The sequence of solutions is undefined if current_stream_control 3 has several so lutions for the current call Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also stream_control 2 stream_device 2 device_control 2 current_device_control 3 IF Prolog V5 3 201 Reference Manual Database Predicate current_visible 2 Query visible predicates current_visible DefModule Predicate Module The predicate current_visible 2 unifies Predicate by backtracking with the predicate indicators of all the visible predicates in the calling module or in the specified Module and DefModule with the name of the module in which Predicate
141. interface an empty input is synonymous with step In the case of the alpha interface empty input lt will either be used to switch between the various display fields on the interface or will be considered synonymous with step depending of the context in which it is used See also skip 0 1 continue 0 nonstop 0 fast_skip 0 1 Reference Manual 660 IF Prolog V5 3 stop 4 stop_interactive 1 2 4 Debugger command Command interface Set explicit breakpoint stop Breakpoint Ports Conditions Actions stop MonitoredVariable BindingType Conditions Actions st Breakpoint Ports Conditions Actions st MonitoredVariable BindingType Conditions Actions stop_interactive Breakpoint si Breakpoint stop_interactive Breakpoint Ports si Breakpoint Ports stop_interactive Breakpoint Ports Conditions Actions stop_interactive MonitoredVariable BindingType Conditions Actions si Breakpoint Ports Conditions Actions si MonitoredVariable BindingType Conditions Actions The commands stop 4 and stop_interactive 1 2 4 are used to declare explicit break points The stop 4 command defines a breakpoint and the stop_interactive 1 2 4 com mand defines an interactive breakpoint There are two kinds of breakpoints Event driven breakpoints An event driven breakpoint is defined by specifying MonitoredVariable and BindingType MonitoredVariabl
142. is a term of another type existence_error global_variable The argument Name is not the name of an existing global variable Hints Global variables are always assigned to a module they can be neither exported nor imported In operations with global variables therefore only those global variables defined in the calling module or in the specified Module are taken into account Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also current_global 1 get_global 2 push_global 2 set_global 2 unset_global 1 IF Prolog V5 3 403 Reference Manual Input output for terms User definable predicate portray 2 User defined output predicate portray Stream Term Body The predicate portray 2 enables the user to influence the output of terms The predicate portray 2 is called by print 1 2 and possibly by write_term 2 3 if it is defined or visible in the module in which the original output predicate is executed If the predicate portray 2 fails or if an exception occurs during execution the term is output as if portray 2 were undefined In the case of structures portray 2 is also called for the output of subterms if portray 2 could not be successfully executed for the full term This allows the user to control the output of specific terms Arguments Stream Stream system defined term Term Term Hints The
143. is equal to 0 the size of free memory equals min max memory_used 100 default_gap minimal_gap maximal_gap Jos otherwise max memory_used 100 default_gap minimal_gap minimal_gap After garbage collection at least minimal_gap bytes of free memory must be available in the area otherwise the size of the data area is automatically in creased maximal_gap After garbage collection a maximum of maximal_gap bytes of free memory must be available otherwise the size of the data area is automatically decreased If this parameter is equal to 0 its value is not involved in calculating the free memory trace Activate deactivate tracing of the garbage collection on the output stream cur rent_error Reference Manual 484 IF Prolog V5 3 set_memory_management 3 Predicate Memory management Arguments Area Atom database global constraints local trail extension Parameter Atom minimal_size maximal_size minimal_gap maximal_ gap default_gap trace Value Integer or integer expression or atom Value on off Exceptions instantiation_error The argument Area Parameter or Value must not be a variable but a variable was specified type_error atom The argument Area Parameter or Value must be an atom but is a term of another type domain_error memory_area The argument Area must specify a memory area of the Prolog system The specified atom is not a valid identifier domain_error memory_parameter
144. is generally not suitable for re input with read_term 2 3 Example user write_formatted lt ENTER gt Result s t n lt ENTER gt Name 7 33 lt ENTER gt Result Name 7 33 yes Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1A The exception domain_error print_format has been changed to domain_ error write_format for more orthogonality See also writeq 1 2 write_term 2 3 write_canonical 1 2 Reference Manual 610 IF Prolog V5 3 write_formatted_atom 3 Predicate Formatted input output for terms Formatted output of terms write_formatted_atom Atom Format TermList The predicate write_formatted_atom 3 outputs the terms specified in TermList to a stream of type string in accordance with the formatting instructions in Format The contents of the string are then unified with Atom The predicate write_formatted_atom 3 is a convenience predicate for using write_for matted 3 with an output stream of type string Please consult the manual entry for write_formatted 2 3 for further information Arguments Atom Atom Format Atom TermList List of terms Exceptions type_error atom The argument Atom must be a variable or an atom but is a term of another type See also write_formatted 2 3 Hints The predicate can be implemented as follows
145. is to be parsed Arguments Argl Atom structure Arg2 Atom structure Hints If you specify additional arguments in Argl or Arg2 then these are inserted before the arguments generated by the system during conversion into Prolog clauses A detailed description of the Prolog grammar rules can be found in F Prolog User s Guide 2 Example An English sentence can very roughly be described as a sequence consisting of a nominal phrase and a verbal phrase In arrow notation it would look like this Reference Manual 44 IF Prolog V5 3 gt 2 Language construct Database sentence gt nom_phrase verb_phrase nom_phrase gt dogs verb_phrase gt bark As soon as these clauses have been read into your database with consult 1 or recon sult 1 you can have a look at their structure by using listing 0 1 for example user listing lt ENTER gt xxx user sentence 2 x sentence A B nom_phrase A C verb_phrase C B user nom_phrase 2 nom_phrase dogs A A h user verb_phrase 2 verb_phrase bark A A yes The rules can be stated like this A list L minus a list LO is a sentence if there is a list L1 such that the first part of L without L1 is a nominal phrase and L1 itself minus the list LO is a verbal phrase A list minus a list L2 is a nominal phrase if the difference consists precisely of the atom dogs A list minus a list L3 is a verbal phrase if the di
146. list The argument Sublist or List must be a list but is a term of another type type_error list The argument Remainder must be a variable or a list but is a term of another type Example Sublist is removed only once user remove a b a b c d a b L lt ENTER gt L c d a b lt ENTER gt yes user remove d e a b c d e f g L lt ENTER gt L a b c f g lt ENTER gt yes The elements of Sublist must be contiguous in List Reference Manual 454 IF Prolog V5 3 remove 3 Predicate List processing user remove a b a c b L lt ENTER gt no The elements must be unifiable sequentially Backtracking does not occur user remove A B a b c d L lt ENTER gt A a B b L c d lt ENTER gt no Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also append 3 member 2 IF Prolog V5 3 455 Reference Manual Execution control Predicate repeat 0 Generate a choice point repeat The predicate repeat 0 is always successful in contrast to the predicate true 0 it is re executable and will succeed any number of times by backtracking The predicate repeat 0 is thus suitable for programming iterative loops in IF Prolog by backtracking Hints Variable instantiations which arise from attempts to satisfy a goal are undone again in the
147. lt Terml Term 2 Term gt Term gt Terml Term 2 Term lt Term2 lt Terml Term 2 Term1 gt Term2 gt Terml Term 2 Terml Q Term2 Term1 Term2 Terml Term2 Terml Term2 The term comparison predicates check the relationship between Term1 and Term2 The following relationships apply to terms of different types Variable lt Floating point Floating point lt Rational number Rational number lt Integer Integer lt Atom Atom lt Structure The following applies to terms of the same type Variable The order is undefined and the result is therefore random Floating point Arithmetic order Rational number Arithmetic order Integer Arithmetic order Atom Character code order Structure Ordered primarily according to their arity then by the name of the functor and finally by the arguments from left to right IF Prolog V5 3 65 Reference Manual Term comparison Predicate lt 2 Q lt 2 gt 2 gt 2 Arguments Term1 Term2 Hints Term Term The atoms lt lt gt gt and are built in as infix operators Although two variables will always be ordered at any one time there is no guarantee that at some later time a comparison of the same two variables will yield the same result For this reason you should never make references to the order of variables
148. lt 127 Exceptions instantiation_error The argument Predicate or After or a subterm must not be a variable but a variable was specified type_error predicate_indicator The argument Predicate must be a predicate indicator i e a structure with the format Functor Arity but is a term of another type IF Prolog V5 3 351 Reference Manual Database Predicate modify_mode 3 type_error atom The name of the predicate Predicate must be an atom type_error integer The arity of the predicate Predicate must be an integer domain_error not_less_then_zero The arity of the predicate Predicate must be a positive integer but is negative representation_error max_arity The arity of the predicate Predicate must be an integer in the range 0 127 but is larger permission_error modify procedure The predicate indicator Predicate specifies a predicate which already exists and is not modifiable or which is the name of a language construct type_error atom The argument After must be an atom but is a term of another type domain_error on_or_off The argument After must be one of the atoms on or off but is another atom type_error atom The argument Before must be a variable or an atom but is a term of another type domain_error on_or_off The argument Before must be a variable or one of the atoms on or off but is another atom permission_error access system_module The predicate modify_mode 3 must not be executed for a
149. lt ENTER gt lt EOF gt yes IF Prolog V5 3 491 Reference Manual System information Predicate set_prolog_flag 2 Standard This predicate complies with the definition of the ISO standard for Prolog The Prolog flags backtrace consult double_quotes extended_syntax float_max float_min iso nested_comments notty prompt read_error report_read_error search_path signal warnings and write_depth are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also current_prolog flag 2 system_parameters 1 Reference Manual 492 IF Prolog V5 3 set_prolog_flag 2 Directive System information Set value of a Prolog flag set_prolog_flag Flag Value The directive set_prolog_flag 2 is analogous to the predicate set_prolog_flag 2 As as directive it is executed by consult 1 reconsult 1 or compile 1 when a Prolog source text is read and takes effect immediately Arguments Flag Atom Value Atom integer or integer expression Exceptions Errors in directives are detected with consult 1 reconsult 1 or compile 1 No exceptions are generated Instead only error messages are output on the current error output stream This directive can produce the following error messages instantiation_error The argument Flag or Value must not be a variable but a variable was specified type_error atom The argument Flag must be
150. module the sequence of their execution is undefined The goals specified by the directives init 1 and initialization 1 are executed after the entire Prolog text has been loaded even if it contains several modules The goals are executed in the context of the module where the directives occurred Arguments Goal Goal Exceptions Errors in directives are detected with consult 1 reconsult 1 or compile 1 No exceptions are generated Instead only error messages are output on the current error output stream These directives can directly produce the following error messages permission_error directive module The specified directive init 1 or initialization 1 is not valid in this position Any exception may occur when Goal is executed Hints The atoms init and initialization are defined as prefix operators Directives are evaluated during consultation see consult 1 reconsult 1 or compi lation see compile 1 procmp command Reference Manual 306 IF Prolog V5 3 init 1 initialization 1 Directive Execution control Example The file example pro contains the following program init write init nl program halt The init 1 directive is executed after consultation prolog c example lt ENTER gt IF PROLOG V5 1 Copyright C Siemens Nixdorf Information Systems AG 1996 init consult example pro loaded in 0 02 sec Standard The directive initialization 1 complies with the definition of the
151. must be a positive integer but is negative Furthermore if an arithmetic expression is specified for the argument Arity all the exceptions for is 2 can occur Example Structure is instantiated user functor f X Y F S lt ENTER gt X _68 Y 69 F f S 2 lt ENTER gt yes user functor a F S lt ENTER gt F a S 0 lt ENTER gt yes user functor g x g 1 lt ENTER gt yes Structure is uninstantiated user functor S f 3 lt ENTER gt S f _114 _115 _116 lt ENTER gt yes user functor S 3 0 lt ENTER gt S 3 lt ENTER gt yes functor 3 is especially useful if structures with a great many arguments are required but only a few of them are instantiated Reference Manual 262 IF Prolog V5 3 functor 3 Predicate Term conversion user functor S f 7 lt ENTER gt arg 3 S here lt ENTER gt S f _136 _137 here _139 _140 _141 _142 lt ENTER gt yes Standard This predicate complies with the definition of the ISO standard for Prolog The use of arithmetic expressions in the argument Arity is not allowed in the ISO standard for Prolog In the ISO compatibility mode see Prolog flag iso therefore no arithmetic expressions may be used as arguments for this predicate Instead an evaluation must be programmed explicitly with the help of is 2 if necessary See also arg 3 2 IF Prolog V5 3 263 Reference Manual Garbage collection Predicate garba
152. named alias associated with Stream eof _action Action Action is unified with the type of handling defined for Stream with open 4 on reaching the end of the stream mode Mode Mode is unified with the I O Mode which was specified when Stream was opened end_of_stream End If the stream position is end_of_stream then End is unified with at else if the stream position is past_end_of_stream then End is unified with past else End is unified with not Reference Manual 540 IF Prolog V5 3 stream_property 2 Predicate Stream processing The predicate stream_property 2 succeeds by backtracking for all those I O streams and their associated properties which were found at the time of the first call even if they have since been closed or if new ones have been added logic update view Arguments Stream Stream system defined term or alias atom Info Structure or atom Exceptions domain_error stream The argument Stream must be a variable or an input output stream supplied by open 3 4 domain_error stream_property The argument Info must be a variable an atom or a structure denoting a stream property but is a term of another type Hints If the argument Stream is instantiated it may be an alias Since the ISO standard allows only a stream as the argument this functionality is not available in the ISO compatibility mode If Stream is a variable stream_property 2 will always instantiate it to an input output stream and
153. never to an alias Positioning is realized by corresponding stream control functions of the device drivers see stream_control 2 The sequence of solutions is undefined if stream_property 2 has several solutions for the current call Example user current_alias user_input S stream_property S 1 lt ENTER gt S stream 0 I file_name standard user_input lt ENTER gt I input lt ENTER gt I mode read T buffer no lt ENTER gt IF Prolog V5 3 541 Reference Manual Stream processing Predicate stream_property 2 I eof_action reset lt ENTER gt I reposition false lt ENTER gt I type text lt ENTER gt I alias user_input lt ENTER gt I alias current_input lt ENTER gt I end_of_stream not lt ENTER gt no Standard This predicate complies with the definition of the ISO standard for Prolog The information buffer is not required by the ISO standard for Prolog There fore it is not available in ISO compatibility mode see Prolog flag iso Compatibility V5 0B ISO conformance the predicate stream_property 2 rejects an alias as the first argument in ISO compatibility mode See also open 3 4 close 1 2 current_alias 2 set_stream_position 2 stream_control 2 stream_device 2 stream_property 2 Reference Manual 542 IF Prolog V5 3 stream_type 2 Predicate Stream processing Query type of an input output stream stream_type Stream
154. of another type domain_error signal_name The argument Signal must be one of the built in signal names but is another atom type_error atom_or_compound The argument Command must be an atom or a structure but is a term of another type domain_error signal_control The value of the argument Command is none of the values permitted for a signal control command Hints The pseudo signal all can be used to execute Command for all signals If clear or received is specified this applies to all signals handled by the passive signal handling mechanism of IF Prolog at the time of the call Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso IF Prolog V5 3 503 Reference Manual Contexts Exceptions Predicate signal_control 2 See also signal_handler 3 current_signal 2 context 2 Reference Manual 504 IF Prolog V5 3 signal_handler 3 Predicate Contexts Exceptions Define local signal handling signal_handler Goal Signal Handler Module The predicate signal_handler 3 executes Goal and enables incoming signals to be handled during the goal processing If Goal succeeds signal_handler 3 is exited with success By backtracking Goal can supply several results If Goal does not or does no longer succeed signal_handler 3 also fails i e backtracking is initiated If a signal is received whil
155. of last modification ctime time of last status change blksize filesystem specific preferred I O block size for this object blocks number of blocks for this object The Value for mode is a list of the following values File type Description ifblk block special Tf chr character special ififo FIFO special ifreg regular ifdir directory iflnk symbolic link IF Prolog V5 3 273 Reference Manual Operating system Predicate get_file_info 2 3 File mode iread iwrite iexec irusr iwusr ixusr irgrp irgrp ixgrp iroth iwoth ixoth isuid isgid isvtx Arguments Pathname Info Attribute Value Exceptions Description file is readable file is writable file is executable file has read permission for owner file has write permission for owner file has execute search permission for owner file has read permission for group file has write permission for group file has execute search permission for group file has read permission for others file has write permission for others file has execute search permission for others set user ID on execution set group ID on execution restricted deletion flag for directories Atom name of a file directory etc List of the form Attribute Value Atom attribute of file Term value of attribute instantiation_error The argument Pathname or a subterm must not be a variable but a variable was specified type_error atom The argument Pathname must be an atom
156. of the preceding number There must be at least one blank between the slash and the opening parenthesis as Prolog would otherwise interpret the input as a normal structure with the functor 107 4 7 253 Blanks are not required as the operator is separated from the preceding operator by the single quotes a likes b Blanks are not required with the delimiting single quotes likes is unambiguously identifiable as an atom 1likes must be defined as an infix operator If the single quotes are omitted delimiters would be required for separation a likes b IF Prolog V5 3 797 Reference Manual Prolog Syntax Terms 9 2 Terms Term is the generic for all syntactic units in Prolog A term may belong to one of the following classes e constant variable e structure e term enclosed in parentheses atom constant number named variable variable anonymous variable term normal structure structure expression non empty list term Test predicates Prolog provides a number of built in predicates that enable you to check what class a term belongs to Predicate tests whether a term is atomic 1 a constant number or atom atom 1 an atom letter 1 an atom consisting of one letter digit 1 an atom consisting of one digit n
157. old value is overwritten This would not be possible with Prolog variables 9 2 3 Structures Unlike constants and variables structures consist of more than one component These indi vidual components in turn may be any terms i e they themselves may also be structures In Prolog structures can be represented syntactically in different ways A structure can be represented as one of the following Reference Manual 808 IF Prolog V5 3 Terms Prolog Syntax e normal structure e expression e non empty list Every structure can be represented as a normal structure which is therefore a general way of representing structures Expressions and lists are special forms which simplify the representation of structures For every expression and every non empty list there is an equivalent normal structure Normal structures A normal structure is defined as follows functor Argument Argument functor must be an atom Argument 1 lt n lt max_arity may be any term The number of arguments is referred to as arity The maximum arity of a structure can be queried with the predicate current_prolog_flag 2 user current_prolog_flag max_arity M M 127 yes Note Some built in predicates interpret atoms as structures with zero arity However the following applies user compound atom no Examples of normal structures parents father mother faculty 10 Result date year 1984 month X
158. on the Debugger in the IF Prolog User s Guide 2 Debugger commands which are adjacent to each other and which are similar in function are described together Debugger commands that are only available in the alpha interface of the debugger are spe cially marked Most commands have a short form which is also listed In debugger commands which in addition to their arguments are supplied with informa tion on the calling module the argument list as in the example is followed by the text Module In this case a module specification can be specified by 2 similar to meta predicates 629 Alpha interface Alpha interface 0 0 0 0 Scrolling forward backward fast_forward fast_backward These commands enable the user to scroll in the current field and scroll line by line forwards and backwards respectively and scroll page by page forwards and backwards respectively If the user has already reached the field boundaries these commands have no effect A plus sign is displayed in the information area of the current field if the field extends beyond the lower edge of the window and a minus sign is displayed if the field extends beyond the upper edge of the window Exceptions domain_error arity The command forward backward fast_forward or fast_backward was called with an incorrect number of parameters Hints These commands are only available in
159. operating system command Execute an operating system command Execute an operating system command with input and output specified Execute an operating system command with input and output specified Spawn process Query process ID of current process Send signal to a process Create a pipe Wait for termination of a child process Wait for termination of a child process Change drive Query drive Start program execution Start program execution Start the operating system command interpreter Execute an operating system command Execute an operating system command Execute an operating system command with input and output specified Execute an operating system command with input and output specified Reference Manual 34 IF Prolog V5 3 Predicates Overview by functionality unix_fork Pid unix_getpid Pid unix_kill Pid Signal unix_wait Pid unix_wait Pid ExitStatus Net communication current_host Host current_socket Domain Type Socket get_socket_option Socket Option Value host_addr Host Addr host_addr Host Addr net_service Service Protocol Port select QStreams Timeout ReadyReadStreams select Streams Timeout ReadyReadStreams ReadyWriteStreams select SocksOrStreams Timeout ReadyReadSOS ReadyWriteSOS Timeleft set_socket_option Socket Option Value socket Domain T ype Socket socket_accept Socket Addr NewSoc
160. operator with a precedence number of 500 and thus itself has precedence 500 thereby contradicting the operator declaration yfx For the result is f the argument in position y is 2 5 and the argument in position xis 2 7 2 so that precedence x lt precedence f As a result is the main functor of the associated normal structure Reference Manual 816 IF Prolog V5 3 Operators Prolog Syntax Similarly the argument 2 7 2 yields as the functor of the associated normal structure This splitting process can be represented in a tree diagram as follows The associated normal structure can be immediately read from the tree The left hand branch represents the first argument of the normal structure and the right hand branch the second argument Both arguments are in turn structures The following normal structure is produced 2 5 2 7 2 If two different operators have the same name then one of these operators must be a prefix operator and the other an infix or postfix operator All other combinations of different operators with the same name are invalid Operators are administered in modules The operations of creating redefining and canceling operators only ever act on the module in which the corresponding operator action was performed Operators are syntactical constructs which are taken into account when terms are read or written If a structure is represented in oper
161. or ppp suffix the suffix pro will be appended to Filename This is then the name of input file The following flags are allowed on the command line a the output is in alphabetical order default u the output is in the order of occurrence in files e only exported predicates are output f output line is not limited to 80 characters Exceptions Prolog exceptions from file access open read may occur existence error source_sink The input file does not exist permission error open source sink The input file cannot be opened for reading Compatibility V5 1A The command procref is new Reference Manual 8 IF Prolog V5 3 prolog System command Prolog system Start of the Prolog system prolog Option Parameter The command prolog starts the Prolog system using the system parameters given in Option The user parameters given in Parameter are not processed by the Prolog system A list of the user arguments specified in the call can be queried by means of user_parameters 1 If after initialization a predicate program 0 is visible then this predicate is called Once it has been executed the Prolog system is exited with the exit value 0 If the predicate program 0 is not visible the Prolog input loop break 0 is started The Prolog session can then be terminated with the call of halt 0O 1 The meanings of the various system arguments are explained in the following root pathname
162. or a subterm must not be a variable but a variable was specified type_error integer The argument Number must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer domain_error not_less_than_zero The argument Number must be a positive integer but is negative domain_error arity The command set_history was called with an incorrect number of parameters Furthermore if an arithmetic expression is specified for the argument Number all the exceptions for is 2 can occur Hints This command is only available in the alpha interface of the debugger See also view_history 0 view_first_screen 0 view_last_screen 0 view_next_screen 0 view_previous_screen 0 Reference Manual 654 IF Prolog V5 3 set_trace_depth 1 Alpha interface Alpha interface Set structure depth for trace outputs set_trace_depth Depth std Depth The set_trace_depth 1 command is used to specify the structure depth for trace outputs to be used for displaying terms Atoms have a structure depth of 0 If terms have a greater nesting depth the terms of the last display depth are displayed with the format Functor or in lists There is no restriction if 0 is specified Arguments Depth Integer or integer expression Depth gt 0 Exceptions instantiation_error The argument Depth or a subterm must not be a variable but a variable was
163. permission_error open source_sink The argument Filename specifies a file or a different I O medium that cannot be opened system_error read system_error write system_error close system_error flush_output system_error interrupted The argument Filename specifies a file for which the indicated error was reported by the operating system during file processing IF Prolog V5 3 155 Reference Manual Database Predicate compile 1 existence_error past_end_of_stream The argument Filename specifies a file for which an unexpected end of file was detected during file processing In addition all the error messages and warnings from read_term 2 assertz 1 and assertz_with_names 2 and may occur These do not cause the load process to be aborted You should be aware that the database may not necessarily contain what you expect it to contain Errors in directives are also output as error messages on the error output stream Un known directives are reported by the error message domain_error directive In the event of errors in a module interface the affected module is deleted after Filename has been processed If there are errors in the declaration part of a module body the affected module body is deleted after Filename has been processed When initialization directives are executed see init 1 any exception may arise These aborts the execution of the initialization goal but does not abort the load process In addition
164. predicate portray 2 is always called with a stream argument even if print 1 or write_term 2 was called or print 2 or write_term 3 was called using an alias Example The empty list is to be printed in a special format user listing lt ENTER gt h xxx user portray 2 portray Stream write Stream empty list yes user print nl lt ENTER gt empty List yes user print a b nl lt ENTER gt a b empty List yes Reference Manual 404 IF Prolog V5 3 portray 2 User definable predicate Input output for terms Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also print 1 2 write_term 2 3 IF Prolog V5 3 405 Reference Manual Database Predicate predicate_mode 3 Query and set the exception mode of a predicate predicate_mode Predicate Before After Module The predicate predicate_mode 3 defines for Predicate whether the exception existence_ error procedure is to be generated if this predicate is not yet or no longer defined see abolish 1 at the time it is called Identification of the predicate is based on its visibility in the calling module or in the specified Module The argument Before is unified with the previously valid mode The exception mode is then set in accordance with the After specification
165. predicate to indicate explicitly the module in which this predicate is visible The predicates activated in the goal are normally executed in the context of the module in which they are defined This does not apply to metapredicates which are executed in the context of calling module or the specified Module unless the 2 qualification is used for a metapredicate to indicate explicitly the module context in which this predicate is to be executed Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1A The predicates profile 1 2 are new See also profile_stat 0 1 profile_reset 0 trace 1 trace_output 4 trace_config 3 debug 1 call 1 set_prolog_flag 2 import 1 Reference Manual 416 IF Prolog V5 3 profile_reset 0 Predicate Profiling Reset profiling statistics profile_reset The predicate profile_reset 0 resets the profiling data Hints The profiling predicates are included in the module profiler This module must be imported before the predicates can be used This predicate is not part of the IF Prolog runtime system and is therefore not available for applications intended for third parties Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1A The predi
166. qualified by means of 2 or 2 with an atom that does not name an existing module Hints The arguments Goall and Goal2 may themselves be composite goals IF Prolog V5 3 53 Reference Manual Execution control Language construct ee The atom is defined as an infix operator The language construct 2 is not a predicate so it cannot be redefined The predicates current_predicate 1 and current_visible 2 do not indicate language constructs Explicit module qualification with 2 or 2 is not permitted for language constructs with the exception of call 1 The predicates activated in the goal must be visible in the specified Module unless the 2 qualification is used for such a predicate to indicate explicitly the module in which this predicate is visible The predicates activated in the goal are normally executed in the context of the module in which they are defined This does not apply to metapredicates which are executed in the context of the specified Module unless the 2 qualification is used for a meta predicate to indicate explicitly the module context in which this predicate is to be executed Example user member X a b member X c lt ENTER gt X a lt ENTER gt X b lt ENTER gt X c lt ENTER gt no user member b a member b b lt ENTER gt yes Standard This language construct complies with the definition of the ISO standard for Prolog See also
167. reconsult 1 Hints If Filename does not contain the extension pro and if a file of this name cannot be found the extension pro is appended and the resultant filename used The predicate reconsult 1 is a metapredicate and manipulates the database in the calling module or in the specified Module If Filename contains module definitions then database manipulation takes place in these modules If not it is implicitly assumed that the contents of Filename belong to the body of the calling module or of the specified Module The difference compared with an explicitly specified body 1 directive at the start of Filename is that the associated body of the module is not first deleted If Filename contains only module interfaces and or bodies then consult 1 and recon sult 1 are prefectly identical The definition of a module interface of an existing module with the same name is first deleted and the definition of a module body overwrites an existing module body The init 1 directives in Filename are also executed in the context of the relevant module If a module in Filename contains several init 1 directives then the execution sequence is undefined Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also consult 1 2 lt gt 2 Reference Manual 448 IF Prolog V5 3 reduce 3 Predicate Term conversion Reduce the
168. remains an actual goal but will only be accessible after the execution of the new current goal has been terminated see PrologClose Therefore nested execution of queries is possible Arguments Query Structure information on the passive Prolog goal See also PrologClose QueryCreate QueryDispose PrologFetch Reference Manual 734 IF Prolog V5 3 sprintt C Function Passive C interface Formatted output of Prolog terms and C data objects include cpro h size_t sprintt char Buffer STRING Format The function sprintt is an extension of the C function sprintf see 10 for Prolog terms An argument in may be either a Prolog term or a normal C data object The arguments are printed in accordance with the formatting specifications in Format The output is printed on the character string pointed at by Buffer Arguments Buffer Pointer to character string Format Character string format specification see write_formatted 2 3 Prolog terms or C data objects in accordance with Format See also outputlen fprintt printt write formatted 2 3 IF Prolog V5 3 735 Reference Manual Device driver interface C Function StreamFlush Flush Prolog output buffer include device h BOOLEAN StreamFlush t_stream Stream long Number The function StreamFlush can be used by the control functions of a device driver in order to cause IF Prolog to fl
169. reset_streams The predicate reset_streams 0 closes all opened input output streams except the default I O streams that were opened at system startup In other words all assignments for the current input output and error output streams are reset to their default values at system startup current input output stream Assignment to default stream current_input user_input current_output user_output current_error user_error Hints If the default streams were redefined with stream__copy 2 the changes cannot be undone with reset_streams 0 Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also set_input 1 set_output 1 set_error 1 current_input 1 current_output 1 current_error 1 stream_copy 2 Reference Manual 458 IF Prolog V5 3 retract 1 2 Predicate Database Remove a clause from database retract Clause Module retract Head Body Module The predicate retract 1 searches the database in the calling module or in the specified Module for clauses which can be unified with Clause If such a clause is found unification of Clause is performed i e any existing variables in Clause are unified with the corresponding arguments or their subterms in the clause found The first clause found is then deleted from the database The predicate retract 2 searches the da
170. see Prolog flag iso See also socket 3 get_socket_option 3 set_socket_option 3 net_service 3 socket_accept 3 socket_bind 2 socket_connect 2 socket_close 1 socket_listen 1 2 socket_receive 2 3 socket_raw_receive 4 5 socket_send 2 3 socket_shutdown 1 2 IF Prolog V5 3 199 Reference Manual Stream processing Predicate current __stream_control 3 Query information on device drivers current_stream_control Stream Command Arity The predicate current_stream_control 3 unifies Command and Arity by backtracking with information on the commands valid for Stream to control input output streams see stream_control 2 This predicate provides a means of checking whether the device driver of an input output stream implements certain functionalities For Stream the name of a device driver may be specified see stream_device 2 so that checks can be carried out before a stream is opened Since IF Prolog can be equipped with any device drivers using its C driver interface it is always best to check whether the driver of the current stream can in fact execute a specific command before using stream_control1 2 Arguments Stream Stream system defined term alias atom or device driver name Command Atom Arity Integer 0 lt Arity lt 127 Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an
171. set_ error 1 Arguments Stream Stream system defined term or alias atom Exceptions domain_error stream_or_alias The argument Stream must be a variable or an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream Hints The predicate error_telling 1 can unify Stream with an alias or the filename that was possibly used with error_tell1 1 or open 4 All error messages and warnings of the Prolog system are output on the current error output stream This stream can always be addressed via the built in alias current_ error as well Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also error_tell 1 error_told 0 set_error 1 current_error 1 seeing 1 telling 1 IF Prolog V5 3 231 Reference Manual Stream processing Predicate error_told 0 Reset current error output stream error_told The predicate error_told 0 resets the default error output stream user_error as the cur rent error output stream If the earlier current error output stream was not a default stream and is not simultaneously the current output stream it is closed see close 1 Hints All error messages and warnings of the Prolog system are output on the current error output stream This stream can always be
172. size tty_size Lines Columns tty_size Stream Lines Columns The predicate tty_size 2 queries the size of the screen associated with the current output stream If there is no screen associated with the current output stream or if the device driver for the stream is not able to supply this information Lines and Columns are unified with 0 The predicate tty_size 3 acts in the same way as tty_size 2 but uses the screen associ ated with the specified output stream Stream Arguments Stream Stream system defined term or alias atom Lines Integer Columns Integer Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error output stream The argument Stream is not a stream which has been opened for output open mode write or append type_error integer The argument Lines or Columns must be a variable or an integer but is a term of another type Hints The terminal control predicates are implemented via the appropriate stream control functions of the device drivers see stream_control 2 IF Pro
173. specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error output stream The argument Stream is not a stream which has been opened for output open mode write or append system_error write system_error close system_error flush_output system_error interrupted The indicated error was reported by the operating system when writing on the output stream Stream Hints Calling n1 0 is equivalent to write n or put_char n The effect of n1 1 is analogous Reference Manual 362 IF Prolog V5 3 Predicate Elementary input output nl 0 1 Example Generating a newline with n1 0 user write peter nl write king lt ENTER gt peter king yes Generating a newline with n user write Hyphen nation lt ENTER gt Hyphen ation yes Standard These predicates comply with the definition of the ISO standard for Prolog See also put_char 1 2 write 1 2 IF Prolog V5 3 363 Reference Manual List processing Predicate nonmember 2 List membership nonmember Element List The predicate nonmember 2 succeeds if Element does not occur in List otherwise it fa
174. specified type_error integer The argument Depth must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer domain_error not_less_than_zero The argument Depth must be a positive integer but is negative domain_error arity The command set_trace_depth 1 was called with an incorrect number of param eters Furthermore if an arithmetic expression is specified for the argument Depth all the exceptions for is 2 can occur See also set_debug_depth 1 IF Prolog V5 3 655 Reference Manual Alpha interface Alpha interface set_trace_length 1 Set length of trace field set_trace_length Length stl Length The set_trace_length 1 command is used to specify the length of the trace field The number of trace messages stored is at least the number specified For reasons of runtime optimization more trace messages than the number specified may be stored at times Arguments Length Integer or integer expression Length gt 0 Exceptions instantiation_error The argument Length or a subterm must not be a variable but a variable was specified type_error integer The argument Length must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer domain_error not_less_than_zero The argument Length must be a positive integer but is negativ
175. specify a valid hostname domain_error internet_address The argument Addr does not specify a valid Internet address Hints The sequence of solutions is undefined if host_addr 2 has several solutions for the current call Reference Manual 294 IF Prolog V5 3 host _addr 2 Predicate Net communication Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also current_host 1 net_service 3 socket 3 IF Prolog V5 3 295 Reference Manual Execution control Predicate if 3 IF THEN ELSE conjunction of goals if ConditionGoal ThenGoal EIseGoal Module The predicate if 3 is used for repeated conditional execution The predicate is analoguous to ConditionGoal gt ThenGoal ElseGoal but in contrast to gt 2 execution can backtrack over ConditionGoal The goal succeeds if ConditionGoal succeeds and ThenGoal succeeds or if the first execution of ConditionGoal fails and ElseGoal succeeds In procedural view this means that ConditionGoal is first executed If this is successful ThenGoal is executed If ThenGoal succeeds the composite goal succeeds as well else the execution backtracks into ConditionGoal If ConditionGoal now succeeds once more ThenGoal is executed again If the first execution of ConditionGoal fails ElseGoal is executed and the composite goal succeeds if ElseGoal
176. stack bytes eused Portion of the extended term stack used in gsize Total size of the global stack bytes gused Portion of the global stack used in tsize Total size of the trail stack bytes tused Portion of the trail stack used in ssize Total size of the stacks bytes sused Portion of the stacks used in maxint Largest representable short 32 64 bit integer minint Smallest representable short 32 64 bit integer Arithmetic functions with arity 1 Res type Functor Function Res type Type Prec Neutral function N N fy 200 Negation N N fy 200 Reference Manual 310 IF Prolog V5 3 is 2 Predicate Arithmetic Arithmetic functions with arity 2 Functor Function Res type Type Prec Addition beet yfx 500 Q Q QI R otherwise Subtraction I 1l I yfx 500 Q Q QI R otherwise Division R N N yfx 400 Integer division I I1 1 yfx 400 rdiv Rational division Q QI rdiv QI yfx 400 mod Modulo function I ImodI yfx 400 rem Division remainder I I rem I yfx 400 Multiplication I I I yfx 400 Q Q Ql Q Q Q R otherwise x Exponentiation R N N xfx 200 min Minimum N min N N max Maximum N max N N Arithmetic functions with arity 1 for type conversion Name Function Res type ceiling N Rounding floating point number up to the next higher I integer float N Conversion of integer into floating point number R floor N Rounding floating point number to the next lower inte I ger round N Rou
177. standard media include cpro h BOOLEAN InitProlog int Number STRING ArgumentVector FILE Input FILE Output FILE Error The function InitProlog initializes IF Prolog in the following sequence e Memory space is allocated for the Prolog database and for the Prolog stack Size definitions given in the argument vector Argument Vector are used e The internal data structures are initialized e The standard media for IF Prolog are defined The stream given in the argument Input will be used as the standard input user_input the stream given in the argument Output will be used as the standard output user_output and the stream given in the argument Error will be used as the standard error output user_error of IF Prolog e The C interface and the device drivers are initialized the function Cboot is called e Files are loaded or consulted if required in the argument vector Argument Vector Number parameters in the argument vector Argument Vector are processed analogous to the start of IF Prolog see system_parameters 1 If the initialization of the IF Prolog was successful InitProlog returns TRUE otherwise it returns FALSE If the initialization is not successful and the reason can be determined by IF Prolog the global variable PrologInitError is set with a string containing an error message Arguments Number Integer size of the Argument Vector Argument Vector Vector of pointers to character str
178. stream current_ input until the character SearchChar is found or the end of the stream is reached All the characters read up to that point are concatenated to form an atom and unified with Text The character SearchChar which caused the termination of the read operation is not included in the resulting atom The predicate get_until 4 acts in the same way for the specified input stream Stream The argument EndChar is unified with SearchChar or the atom end_of_file depending on what led to termination of the read operation end_of_file can be used as the SearchChar so you can read to the end of the stream when the end is reached the predicate succeeds In this case EndChar is unified with end_of_file The predicates succeed if unification of the result atom with Text succeeds and unification of the reason for termination with EndChar succeeds Otherwise the predicates fail Arguments Stream Stream system defined term or alias atom SearchChar Character or end_of_file Text Atom EndChar Character or end_of_file Exceptions instantiation_error The argument Stream or SearchChar must not be a variable but a variable was specified type_error character The argument SearchChar must be a character or the special atom end_of_file but is a term of another type or an invalid atom type_error atom The argument Text must be a variable or an atom but is a term of another type type_error in_character The argument EndChar must be
179. structure Arity Integer 0 lt Arity lt 127 Arity term variables Exceptions The following errors cause IF Prolog to be exited implementation_error Arity arity out of range The argument Arity is not within the range 0 127 implementation_error TermMakeCompound out of memory The function TermMakeCompound could not be executed successfully due to a lack of memory Example The following simple C function realizes a predicate make_indicator 3 which makes a predicate indicator from given name and arity include cpred h BOOLEAN make_indicator_3 void xx make_indicator Functor Arity Indicator STRING string long value TERM functor PrologArg 1 IF Prolog V5 3 765 Reference Manual Active C interface C Function TermMakeCompound TERM arity PrologArg 2 return TermIsAtom functor amp string amp amp TermIsInteger arity amp value amp amp TermUnify PrologArg 3 TermMakeCompound 2 functor arity void Cboot void CPRIM make_indicator 3 make_indicator_3 See also TermMakeFunctor TermMakeUniversal TermlsCompound Reference Manual 766 IF Prolog V5 3 Term MakeF loat C Function Active C interface Generate a Prolog floating point number include cpred h TERM TermMakeFloat double Value The function TermMakeFloat generates a Prolog floating point number and returns it as the result Arguments Va
180. succeeds otherwise it fails The subgoal ThenGoal is therefore executed if the first execution of ConditionGoal succeeds and ElseGoal is only executed if it fails By backtracking ConditionGoal ThenGoal and ElseGoal can have several solutions If ConditionGoal is a composite goal and if it contains a cut 0 then this cut will have no effect beyond the ConditionGoal Arguments ConditionGoal Goal ThenGoal Goal ElseGoal Goal Exceptions instantiation_error The argument ConditionGoal ThenGoal or ElseGoal must not be a variable but a variable was specified type_error callable The argument ConditionGoal ThenGoal or ElseGoal must have the syntactical structure of a Prolog goal existence_error procedure In executing ConditionGoal ThenGoal or ElseGoal a predicate was to be activated which is not defined and the Prolog flag unknown has the value error Reference Manual 296 IF Prolog V5 3 if 3 Predicate Execution control type_error atom The argument ConditionGoal ThenGoal or ElseGoal or a subgoal has been qual ified by means of 2 or 2 with a term that is not an atom existence_error module The argument ConditionGoal ThenGoal or ElseGoal or a subgoal is qualified by means of 2 or 2 with an atom that does not name an existing module Hints The call ConditionGoal gt ThenGoal ElseGoal is equivalent to if ConditionGoal ThenGoal ElseGoal The predicate if 3 is a metapredicate and calls
181. supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream domain_error file_name The value of the argument Stream is not a valid name for a file permission_error output stream The argument Stream is not a stream which has been opened for output open mode write or append permission_error open source_sink The argument Stream specifies a file or a different I O medium that cannot be opened existence_error stream The argument Stream must be associated with an open input output stream Hints All error messages and warnings of the Prolog system are output on the current error output stream This stream can always be addressed via the built in alias current_ error as well IF Prolog V5 3 229 Reference Manual Stream processing Predicate error_tell 1 Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also error_telling 1 error_told 0 set_error 1 see 1 tell 1 open 3 4 assign_alias 2 Reference Manual 230 IF Prolog V5 3 error_telling 1 Predicate Stream processing Query current error output stream error_telling Stream The predicate error_telling 1 unifies Stream with the current error output stream The current error output stream may be a stream that was set with error_tell 1 or
182. the range 0 127 but is larger permission_error modify procedure The predicate indicator Predicate in PredicateList specifies a predicate which al ready exists and is not modifiable or which is the name of a language construct permission_error directive module The specified directive multifile 1 is not valid in this position Hints The atom multifile is defined as a prefix operator Directives are evaluated during consultation see consult 1 reconsult 1 or compi lation see compile 1 procmp command Standard The directive multifile 1 complies with the definition of the ISO standard for Prolog See also consult 1 dynamic 1 discontiguous 1 IF Prolog V5 3 359 Reference Manual Net communication Predicate net_service 3 Query communication service net_service Service Protocol Port The predicate net_service 3 queries the protocol name and port number of a TCP IP service The argument Service specifies the name of the TCP IP service If Protocol is instantiated it must be either tcp or udp representing stream or datagram protocol Otherwise the argument Protocol is unified with the protocol name of the service The predicate is not backtrackable even if there are both tcp and udp services for the specified Service The argument Port is unified with the port number of the service The information is obtained either from the NIS service or the services database on UNIX etc ser
183. the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1A The value of the Prolog flags bounded max_integer and min_integer depends on whether Multiple Precision Integer and Rational Number Support has been configured See also set_prolog flag 2 system_parameters 1 Reference Manual 196 IF Prolog V5 3 current_signal 2 Predicate Contexts Exceptions Query signals and modes current_signal Signal Mode The predicate current_signal 2 unifies Signal by backtracking with all the signal names known in IF Prolog and Mode with their current processing mode The following signal names are known Prolog name C name interrupt SIGINT abort SIGABRT alarm SIGALRM pipe SIGPIPE quit SIGQUIT termination SIGTERM user_1 SIGUSR1 user_2 SIGUSR2 The processing modes for signals are on off default or ignore see signal_control 2 The predicate current_signal 2 succeeds by backtracking for all the signals and modes which were set at the time of the first call even if they have since been modified logic update view Arguments Signal Atom abort alarm interrupt pipe quit termination user_1 user_2 Mode Atom on off default ignore Exceptions type_error atom The argument Signal or Mode must be a variable or an atom but is a term of another type Hints The sequence of solutions is undefined if current_sign
184. the alpha interface of the debugger Reference Manual 630 IF Prolog V5 3 abort 0 Debugger command Command interface Terminate interactive debugger abort A The abort 0 command aborts the debugger session The predicate being tested is evaluated with fail Exceptions domain_error arity The command abort 0 was called with an incorrect number of parameters See also break 0 call 1 IF Prolog V5 3 631 Reference Manual Command interface Debugger command activate_stop 0 1 Reactivate breakpoint activate_stop as activate_stop Numbers as Numbers The activate_stop 1 command activates the explicit breakpoints specified using the Num bers argument If Numbers is omitted all current explicit breakpoints are activated An integer or list of integers may be specified as the argument If a list is specified all the breakpoints included in the list are activated Arguments Numbers Integer or integer expression or a list of integers or integer ex pressions Numbers gt 0 Exceptions instantiation_error The argument Numbers or a subterm must not be a variable but a variable was specified type_error integer_or_list The argument Numbers must be an integer an integer expression or a list of integers or integer expressions but is a term of another type or the result of the evaluation of the expression is not an integer domain_error not_less_than_zero The argument
185. the definition of the ISO standard for Prolog See also atom 1 atomic 1 cyclic 1 float 1 ground 1 integer 1 nonvar 1 number 1 rational 1 var 1 Reference Manual 158 IF Prolog V5 3 concat_atom 2 3 Predicate String processing Concatenate individual atoms to form an atom concat_atom List Atom concat_atom List Delimiter Atom The predicates concat_atom 2 3 concatenate the elements specified in List to form an atom and unify this with Atom If integers occur in List they are converted beforehand into atoms see write_atom 2 The predicate concat_atom 3 acts in the same way as concat_atom 2 but inserts the atom Delimiter between every pair of elements in List Arguments List List of atoms and or integers Delimiter Atom Atom Atom Exceptions instantiation_error The argument Delimiter or List or a subterm must not be a variable but a variable was specified type_error list The argument List must be a list but is a term of another type type_error atom_or_integer An element of List must be an atom an integer or an integer expression but is a term of another type type_error atom The argument Delimiter must be an atom but is a term of another type type_error atom The argument Atom must be a variable or an atom but is a term of another type Example user concat_atom a b c A lt ENTER gt A abc lt ENTER gt yes IF Prolog V5 3 159 Reference M
186. the environment variable SHELL This environment variable usually defines the login shell of a user and is set to a default value by the operating system If the environment variable is not set the default command interpreter for the operating system UNIX Bourne shell is started The predicate succeeds when the shell is exited This makes it possible to work with the operating system interactively without quitting IF Prolog Exceptions system_error command_failed A command passed to the operating system or a corresponding operating system function could not be executed successfully Hints This predicate is system dependent and may not be available on all operating systems Example user system lt ENTER gt pwd lt ENTER gt usri pri ls pro lt ENTER gt widgets pro lt EOF gt yes user Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Reference Manual 550 IF Prolog V5 3 system 0 Predicate Operating system See also system 1 2 3 5 getenv 2 IF Prolog V5 3 551 Reference Manual Operating system Predicate system 1 2 Execute an operating system command system Command system Command ExitStatus The predicate system 1 executes Command in the operating system environment using system 3C in 10 After the specified command is completed the p
187. the first call and not during back tracking of the complex C function This call must take place before the first unification Hints A detailed description of macros used in the example to get a more clear implementation of complex C predicates COROUTINE etc can be found in the F Prolog User s Guide 2 Example The predicate readchar D Z opens at the first call the file D reads the first character and unifies it with Z With backtracking each next character will be read in and unified with Z The file will be closed at the end of the file or when backtracking is cut off see 1 0 include lt stdio h gt include cpred h typedef struct FILE fp readstate COROUTINE readchar readstate state RESUME 1 1label1 HASEPILOG BEGIN STRING filename int c if TermIsAtom PrologArg 1 amp filename FAIL if state gt fp fopen filename r NULL FAIL PrologEnableEpilog IF Prolog V5 3 719 Reference Manual Active C interface C Function PrologEnableEpilog while c fgetc state gt fp EOF if TermUnifyInteger PrologArg 2 long c DETACH 1 1label11 else PrologUndo EPILOG fclose state gt fp END void Cboot void CPRED readchar 2 readchar sizeof readstate See also 1 0 Reference Manual 720 IF Prolog V5 3 PrologError C Function Passive C interface Query error include cpro h BOOLEAN
188. the form Functor Arity Functor Atom Arity Integer 0 lt Arity lt 127 Exceptions instantiation_error The argument Predicate or a subterm must not be a variable but a variable was specified type_error predicate_indicator The argument Predicate must be a predicate indicator i e a structure with the format Functor Arity but is a term of another type type_error atom The name of the predicate Predicate must be an atom type_error integer The arity of the predicate Predicate must be an integer domain_error not_less_then_zero The arity of the predicate Predicate must be a positive integer but is negative representation_error max_arity The arity of the predicate Predicate must be an integer in the range 0 127 but is larger permission_error modify procedure The predicate indicator Predicate specifies a predicate which already exists and is not modifiable or which is the name of a language construct permission_error modify static_procedure The argument Predicate specifies an existing predicate which has not been declared as dynamic and therefore cannot be modified IF Prolog V5 3 73 Reference Manual Database Predicate abolish 1 Hints The predicate abolish 1 is a metapredicate and manipulates the database in the calling module or in the specified Module A predicate may have certain attributes which when it is created are set implicitly by the system according to the current environment or decl
189. type Example The file example pro contains the following Prolog program program user_parameters List write List nl Calling IF Prolog as shown below would then return prolog c example debug data hello lt ENTER gt IF PROLOG V5 1 Copyright C Siemens Nixdorf Information Systems AG 1996 consult example pro loaded in 0 02 sec debug data hello Reference Manual 596 IF Prolog V5 3 user_parameters 1 Predicate System information Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also program_parameters 1 system_parameters 1 IF Prolog V5 3 597 Reference Manual Term classification Predicate var 1 Test for variable var TestTerm The predicate var 1 succeeds if TestTerm is an uninstantiated variable otherwise it fails Arguments Test Term Term Example user var X lt ENTER gt X _68 lt ENTER gt yes user var atom lt ENTER gt no user X is 3 2 var X lt ENTER gt no Standard This predicate complies with the definition of the ISO standard for Prolog See also atom 1 atomic 1 compound 1 cyclic 1 float 1 ground 1 integer 1 nonvar 1 number 1 rational 1 var 1 Reference Manual 598 IF Prolog V5 3 windows_chdrive 1 Predicate Operating system Change drive windows_chdrive
190. undefined if current_char_conversion 2 has several solutions for the current call Standard This predicate complies with the definition of the ISO standard for Prolog See also char_conversion 2 Reference Manual 174 IF Prolog V5 3 current_default_module 1 Predicate Module concept Query current module current_default_module Module The predicate current_default_module 1 unifies Module with the name of the current module Arguments Module Atom name of a module Exceptions type_error atom The argument Module must be a variable or an atom but is a term of another type Hints When IF Prolog starts the built in module user is the current module In the input loop of IF Prolog break 0 the current module is always shown in the prompt All Prolog queries entered in the input loop of IF Prolog break 0 are executed in the current module unless the goal contains explicit module qualifications with 2 Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also 2 module 1 set_default_module 1 current_module 1 IF Prolog V5 3 175 Reference Manual Stream processing Predicate current _device_control 3 Query information on device drivers current_device_control Device Command Arity The predicate current_device_control 3 unifies Command and Ar
191. unify C Function Term UnifyFloat Unify with floating point number include cpred h BOOLEAN TermUnifyFloat TERM Term double Value The function TermUnifyFloat unifies the term Term with a term that corresponds to the floating point number Value If unification is successful the function returns TRUE otherwise it returns FALSE Arguments Term Term variable Value Floating point number Hints The call of TermUnifyFloat Term Wert is except for optimization identical to TermUnify Term TermMakeFloat Wert See also TermUnify TermMakeFloat Reference Manual 784 IF Prolog V5 3 Term Unify Functor C Function Active C interface Unify term with structure include cpred h BOOLEAN TermUnifyFunctor TERM Term STRING Functor ARITY Arity The function TermUnifyFunctor unifies the term Term with a structure with the name Functor and the arity Arity the arguments of which are uninstantiated variables If unification is successful the function returns TRUE otherwise it returns FALSE Arguments Term Term variable Functor Character string name of the structure Arity Integer 0 lt Arity lt 127 Exceptions The following errors cause IF Prolog to be exited implementation_error Arity arity out of range The argument Arity is not within the range 0 127 implementation_error TermUnifyFunctor out of memory The function TermUnifyFuncto
192. unix_fork 1 Spawn process unix_fork Pid The predicate unix_fork 1 duplicates the current IF Prolog process by creating a new process which is the child of the current IF Prolog process and which runs IF Prolog with the same processing status as its parent The predicate succeeds in both processes except that Pid is unified with the number of the child process in the parent process and with 0 in the child process Arguments Pid Integer Exceptions system_error fork_failed No new process could be created This is often due to resource bottlenecks or limitations in the operating system type_error integer The argument Pid must be a variable or an integer but is a term of another type Hints The distinction of the return value for Pid can be subsequently used to enter different program branches in parent and child process The duplicated IF Prolog system in the child process can also be overlaid with some other program using exec 1 2 The distinction could also be used to try out changes in the database without affecting the original IF Prolog system The predicate unix_fork 1 is based on the C function fork 2 see 10 This predicate is system dependent and may not be available on all operating systems Example The following predicate creates a genuine duplicate of the IF Prolog system The second input loop thus operates in a child process user listing lt ENTER gt xxx user te
193. used only once within a clause the anonymous variable can and should be used to emphasize this fact If you use an anonymous variable in a toplevel Prolog query no variable instantiation will be output for the anonymous variable Single variable check Prolog assumes that a variable with a name beginning with a character other than _ will be used to create relationships within a clause and must therefore be used more than once An appropriate check is carried out when the Prolog program is read in The occurrence of variables which are used only once is reported with the message warning single_ variable This is a good way of detecting typing errors which would otherwise affect the behavior of Prolog programs This check is not carried out for variables which begin with an underscore You can use this fact for example to make programs easier to read fact _NO _SINGLE _VAR _CHECK Examples for variable X Key_8 License_plate ancestor BOSS H1 Global variables The global variable concept differs considerably from that of the usual Prolog variables being derived more from the variable concept of procedural programming languages such as C and Fortran Global variables are assigned values not by unification but by calling special predicates set_global 2 push_global 2 Name The name of a global variable is an atom Reference Manual 806 IF Prolog V5 3 Terms Prolog Syntax Definition Global variables are
194. user memberchk a c s c a lt ENTER gt yes IF Prolog V5 3 347 Reference Manual List processing Predicate memberchk 2 The list must not necessarily be ground instantiated As soon as a unifiable element is found the predicate succeeds deterministically user memberchk a c X c a lt ENTER gt X a lt ENTER gt no An empty list contains nothing user memberchk X lt ENTER gt no Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1A The predicate memberchk 2 is new See also member 2 nonmember 2 Reference Manual 348 IF Prolog V5 3 meta 1 Directive Module concept Declare metapredicates meta PredicateList meta PredicateList The directive meta 1 is used to declare the predicates specified in PredicateList as metapre dicates The directive meta 1 may occur in the module interface and in the declaration part of a module body If meta 1 occurs in the module interface it implies export 1 for the specified predicates If the directive meta 1 occurs in the module body it must appear before the first predicate definition Predicates declared with the directive meta 1 are also implicitly declared by private 1 Metapredicates are automatically executed in the context of the calling module instead of the normal practice of ex
195. was defined A predicate is regarded as visible in a module if it was defined or declared in this module or if it was imported from another module The predicate current_visible 2 succeeds by backtracking for all the predicates which were visible at the time of the first call even if they have since been deleted or if other associations have been added logic update view Arguments DefModule Atom name of a module Predicate Structure with the format Functor Arity Functor Atom Arity Integer 0 lt Arity lt 127 Exceptions permission_error access system_module The predicate current_visible 2 must not be executed for a system module type_error atom The argument DefModule must be a variable or an atom but is a term of another type type_error predicate_indicator The argument Predicate must be a variable or a predicate indicator i e a structure with the format Functor Arity but is a term of another type Hints The sequence of solutions is undefined if current_visible 2 has several solutions for the current call The built in predicates are visible in each module without having to be explicitly im ported The language constructs such as gt 2 are not predicates and are therefore not supplied by current_visible 2 Reference Manual 202 IF Prolog V5 3 current_visible 2 Predicate Database Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO co
196. with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream instantiation_error The argument Actions or a subterm must not be a variable but a variable was specified Reference Manual 150 IF Prolog V5 3 close 1 2 Predicate Stream processing type_error list The argument Actions must be a list but is a term of another type domain_error close_option The argument Actions specifies an option that is not permitted for close 2 system_error write system_error close system_error flush_output system_error interrupted The indicated error was reported by the operating system when writing on the output stream Stream Hints It depends on the device as to whether specifying Actions has an effect on the behavior of the device driver Often it will be impossible that the stream cannot be closed successfully Standard This predicate complies with the definition of the ISO standard for Prolog See also open 3 4 IF Prolog V5 3 151 Reference Manual Term comparison Predicate compare 3 Compare terms compare Op Terml Term2 The predicate compare 3 checks the relationship between Term and Term2 The argument Op is unified with one of the following atoms The terms are identical lt Term is smaller than Term2 gt Term1 is greater than Term2 The following relationships
197. yfx 500 lt lt Bitwise left shift I I lt lt I yfx 400 gt gt Bitwise right shift I I gt gt I yfx 400 Reference Manual 312 IF Prolog V5 3 Predicate Arithmetic Arguments Result Term usually number Expression Number or arithmetic expression Exceptions instantiation_error The argument Expression or a subterm must not be a variable but a variable was specified type_error evaluable The argument Expression must be a number or an evaluable arithmetic expression but is a term of another type or an operation in the expression Expression requires a number as an argument but a different term was specified type_error integer An operation in the expression Expression requires an integer as an argument but a term of another type was specified type_error float An operation in the expression Expression requires a floating point number as an argument but a term of another type was specified type_error number An operation in the expression Expression requires a number as an argument but a term of another type was specified domain_error single_precision_integer An operation in the expression Expression requires an integer with machine preci sion as an argument but a big number was specified evaluation_error int_overflow An arithmetic overflow was detected during the evaluation of Expression evaluation_error float_overflow An arithmetic overflow was detected during the evaluation of Expression evalua
198. 1 V X _150 Y _151 S X _150 lt ENTER gt yes user read_term T syntax_errors error lt ENTER gt a X Y lt ENTER gt eek EXCEPT ION syntax_error gt gt gt line 4 gt gt gt column 5 gt gt gt syntax_error operator expected gt gt gt goal system read_term _119 syntax_errors error no user read_term T syntax_errors fail lt ENTER gt a lt ENTER gt xxx Syntax_error start of term expected gt gt gt line 4 column 3 no Reference Manual 444 IF Prolog V5 3 read_term 2 3 Predicate Input output for terms user read_term T syntax_errors quiet lt ENTER gt d f lt ENTER gt no user read_term T variable_names V lt ENTER gt a _ C lt ENTER gt T a _131 _132 V C _132 lt ENTER gt yes Standard These predicates comply with the definition of the ISO standard for Prolog The options syntax_errors and varnames are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso Compatibility V5 0B ISO conformance exception permission_error input binary_stream is gen erated instead of permission_error input text_stream when the stream is not a text stream See also read 1 2 read_error 2 3 syntax_error 2 IF Prolog V5 3 445 Reference Manual Database Predicate reconsult 1 Read in
199. 1 Reference Manual List processing Predicate connect 3 user connect h t X Y lt ENTER gt X h Y t lt ENTER gt yes The call can also be made exclusively with uninstantiated variables user connect X Y Z X Y Z lt ENTER gt X _69 _70 Y _69 Z _70 lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also append 3 Reference Manual 162 IF Prolog V5 3 consult 1 Predicate Database Read in a Prolog file consult Filename Module Filename Module The predicate consult 1 reads the file Filename into the database in the calling module or in the specified Module To enable Prolog text to be entered interactively as well the atom user may also be specified for Filename In this case consult 1 reads from the current input stream and displays a gt gt prompt to indicate that a clause or a directive is expected and a prompt to indicate that a clause or a directive that has already begun has not yet been completed By entering end_of_file or pressing the appropriate key it is possible to terminate the consult process Clauses occurring in Filename are read in with read_term 2 checked for correct syntax and inserted with assertz 1 or assertz_with_names 2 into the database of the relevant module Clauses with syntax errors
200. 150 fx import op 1150 fx meta op 1150 fx end_module op 1150 fx begin_module op 1150 x module op 1150 fx ensure_loaded op 1150 fx include op 1150 fx initialization op 1150 fx init op 1150 fx private op 1150 fx dynamic op 1150 fx multifile op 1150 fx discontiguous op 1200 xfx gt op 1200 xfx op 1200 fx op 1200 fx no Standard This predicate complies with the definition of the ISO standard for Prolog See also op 3 Reference Manual 188 IF Prolog V5 3 current _output 1 Predicate Stream processing Query current output stream current_output Stream The predicate current_output 1 unifies Stream with the current output stream Arguments Stream Stream system defined term Exceptions domain_error stream The argument Stream must be a variable or an input output stream supplied by open 3 4 Hints The predicate current_output 1 will never unify Stream with an alias or the filename that was possibly used with tel1 1 or open 4 Standard This predicate complies with the definition of the ISO standard for Prolog See also current _input 1 current_error 1 telling 1 set_input 1 set_output 1 set_error 1 IF Prolog V5 3 189 Reference Manual Database Predicate current_predicate 1 Query visible predicates current_predicate Predicate Module The predicate current_predicate 1 unifies Pred
201. 2 write_term 2 3 write_canonical 1 2 read_term 2 3 Reference Manual 602 IF Prolog V5 3 write_atom 2 Predicate Term conversion Convert a term into an atom write_atom Term Atom The predicate write_atom 2 converts Term into an atom taking the operator definitions into account and unifies the result with Atom Conversion to an atom occurs as with write 1 i e special characters in atoms are not treated specially in the output Arguments Term Term Atom Atom Exceptions type_error atom The argument Atom must be a variable or an atom but is a term of another type Hints The call write_atom Term Atom is identical to open string test write S write S Term stream_control S string Atom close S An atom created by write_atom 2 is generally not suitable for re input e g with parse_atom 6 Example user write_atom a b tc A lt ENTER gt A a b c lt ENTER gt yes IF Prolog V5 3 603 Reference Manual Term conversion Predicate write_atom 2 user write_atom b 3 0 A lt ENTER gt A b 3 lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also writeq_atom 2 write 1 2 write_term 2 3 parse_atom 6 stream_control 2 Reference Manual 604 IF Prolog V5 3 write_canonical 1 2 Predicate
202. 2 224 2254 2 ee bb eae oe Bs 155 compound 1 Test for Sree lt o ccn u kor ee branio eR Ee ee SS 157 concat_atom 2 3 Concatenate individual atoms to form an atom 159 connect 3 Connect a head and a tail to form a list 161 consult 1 Read ima Prolog file etoson a aisi aO kS n OE a Rw 163 ntext 2 Create a CON secs e mocone mmeo e ahed e E 166 copy_term 2 Create a term COpy ooo aa a 170 create_array 2 Create an array o oo eee ee ee es 171 current_alias 2 Query aliases of input output streams current_char_conversion 2 Information on character conversions current_default_module 1 Query current module current_device_control 3 Query information on device drivers current_error 1 Query current error output stream current_global 1 Query global variables current_host 1 Query names of current host current_input 1 Query current input stream current_language 1 Query current language current_memory_management 3 Query memory management parameters eurrent_module 1 Query modules 2 282 464 42884 wo os current_op 3 Information on operators 48 current_output 1 Query current output stream current_predicate 1 Query visible predicates current _prolog_flag 2 Query Prolog fags gt s oo ss e aa
203. 2 3 match Atom the regular expression RegExp The predicates succeed when Atom or a subatom of Atom matches RegExp otherwise they fail With regexp 3 the matching subatoms of Atom can be retrieved in List RegExp can be formed as follows c The character c where c is not a special character c The character c where c is any character except a digit in the range 1 9 The beginning of the atom compared The end of the atom compared Any character in the atom s Any character in the set s where s is a character and or a range e g c f s Any character not in the set s where s is defined as above r Zero or more successive occurrences of the regular expression r The longest match is chosen rx The occurrence of regular expression r followed by the occurrence of regular expression x Concatenation r m n Any number of m through n successive occurrences of the regular expression r The regular expression r m matches exactly m occurrences r m matches at least m occurrences eae The subatom matching the regular expression r is returned in the result list List Arguments RegExp Atom a regular expression Atom Atom List List of atoms Reference Manual 452 IF Prolog V5 3 regexp 2 3 Predicate Regular expressions Exceptions type_error atom The argument RegExp must be an atom but is a term of another type type_error atom The argument Atom must be an atom but is a term of another type ty
204. 3 trace_config 3 Predicate Tracing Exceptions instantiation_error The argument Parameter or New or a subterm must not be a variable but a variable was specified type_error atom The argument Parameter must be an atom but is a term of another type domain_error config_option The argument Parameter is not a valid configuration parameter type_error integer The argument New must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer domain_error not_less_than_zero The argument New must be a positive integer but is negative type_error atom The argument New must be an atom but is a term of another type domain_error on_or_off The argument New must be one of the atoms on or off but is another atom Furthermore if an arithmetic expression is specified for the argument New all the exceptions for is 2 can occur Hints This predicate is not part of the IF Prolog runtime system and is therefore not available for applications intended for third parties Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also trace 1 debug_config 3 IF Prolog V5 3 577 Reference Manual Tracing User definable predicate trace_end 0 User defined termination of the tracer trace_end Body The predicate trace_e
205. 3 socket _shutdown 1 2 set_socket_option 3 IF Prolog V5 3 517 Reference Manual Net communication Predicate socket _listen 1 2 Listen for connections socket _listen Socket socket _listen Socket Quelen The predicates socket_listen 1 2 listen for connections on a socket The argument Socket specifies a stream socket opened by socket 3 The argument Quelen specifies the maximum length the queue of pending connections may grow to If a connection request arrives with the queue full the client may receive an error or the request may be ignored so that retries may succeed The predicate socket_listen 1 acts like socket_listen 2 with Quelen 1 Arguments Socket Socket system defined term Quelen Integer Exceptions instantiation_error The argument Socket must not be a variable but a variable was specified type_error socket The argument Socket must be a socket supplied by socket 3 but is a term of another type domain_error socket The argument Socket must be a currently open socket supplied by socket 3 domain_error stream_socket The argument Socket must be a stream socket but is a socket of another type type_error integer The argument Quelen must be an integer but is a term of another type Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also alarm 1 socket 3 curr
206. 37 442 Reconfigure Prolog 6 reexport predicates 450 reference backward chained 17 forward chained 17 regular expression match 452 rem 309 Remove explicit breakpoints 651 return key delimiter function 796 disabling 797 reverse list 463 right shift 309 round 309 screen clear 148 clear line 144 clear to end 146 determine cursor position 277 query size 581 Scrolling 630 separators 795 sequence of integers generate 258 serial number of IF Prolog system 424 Set debugger port 649 Set explicit breakpoint 661 Set length of trace field 656 Set structure depth 653 Set structure depth for trace outputs 655 Set trace ports 668 shell Reference Manual 842 IF Prolog V5 3 Index start 550 Show dynamic call chain 672 sign 309 signal control 502 handle 166 505 query 197 send to process 588 signum 309 simple C function add to a module 709 sin 309 sine 309 sinh 309 size database 309 global stack 309 local control stack 309 stacks 309 trail stack 309 sort a list 527 special characters 794 sqrt 309 square root 309 ssize 309 stack size 309 used 309 Start new input loop 637 start shell 666 statistics profile 417 418 Store field 658 stream input line 247 position of line 247 redefine 535 string syntax analysis 392 structure access arguments 80 arity 809 convert to list 60 determine arity 261 determine functor 261 generate 261 765
207. 4 Hints The sequence of solutions is undefined if current_alias 2 has several solutions for the current call Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also assign_alias 2 cancel_alias 1 IF Prolog V5 3 173 Reference Manual Input output for terms Predicate current_char_conversion 2 Information on character conversions current_char_conversion CharacterIn CharacterOut The predicate current_char_conversion 2 supplies information on the currently defined character conversions Information is supplied only on conversions that do not map charac ters onto themselves During backtracking CharacterIn and CharacterOut are unified with a single character This involves mapping the character CharacterIn to the character CharacterOut provided that this character is not enclosed in single or double quotes and is not used as a character constant The predicate current_char_conversion 2 succeeds by backtracking for all CharacterIn and CharacterOut pairs which were defined at the time of the first call even if the definitions have since been modified logic update view Arguments CharacterIn Character CharacterOut Character Exceptions type_error character The argument CharacterIn or CharacterOut must be a variable or a character but is a term of another type Hints The sequence of solutions is
208. 5 Reference Manual 284 IF Prolog V5 3 getewd 1 Predicate Operating system Query current working directory getcwd Dir The predicate getcwd 1 unifies Dir with the full pathname of the current working directory Arguments Dir Atom Exceptions type_error atom The argument Dir must be a variable or an atom but is a term of another type Hints The predicate getcwd 1 is based on the C function getcwd 3C see 10 The structure of pathnames is operating system dependent Example user getcwd Dir lt ENTER gt Dir usr lib lt ENTER gt yes user chdir getcwd Dir lt ENTER gt Dir usr lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso IF Prolog V5 3 285 Reference Manual Operating system Predicate getewd 1 See also chdir 1 windows_chdrive 1 windows_getdrive 1 Reference Manual 286 IF Prolog V5 3 getenv 2 Predicate Operating system Query environment variable getenv Name Value The predicate getenv 2 unifies Value with the value of the environment variable Name If such a variable does not exist getenv 2 fails Arguments Name Atom Value Atom Exceptions instantiation_error The argument Name must not be a variable but a variable was specified type_error atom The argument Name must
209. 5 3 C interface Overview by functionality Test results passive C interface C Function TERM PrologGoal t_cursor ActGoal BOOLEAN PrologIsFloat t_cursor ActGoal STRING VarName double Value BOOLEAN PrologIsInteger t_cursor ActGoal STRING VarName long Value BOOLEAN PrologIsString t_cursor ActGoal STRING VarName STRING Name BOOLEAN PrologIsTerm t_cursor ActGoal STRING VarName TERM Term Connect to Prolog C Function void Cboot void void CPRED STRING Functor ARITY Arity CPREDFUN Function size_t Size void CPRIM STRING Functor ARITY Arity CPRIMFUN Function void Cshutdown void void MCPRED STRING Module STRING Functor ARITY Arity CPREDFUN Function size_t Size void MCPRIM STRING Module STRING Functor ARITY Arity CPRIMFUN Function TERM PrologArg ARITY Argno Functionality Prolog goal as term Get floating point number from variable Get integer from variable Get character string from variable Get Prolog term from variable Functionality Link a C function to IF Prolog Add a complex C function to IF Prolog Add a simple C function to IF Prolog Call a C function on IF Prolog shutdown Add a complex C function to a module Add a simple C function to a module Access predicate arguments IF Prolog V5 3 685 Reference Manual Overview by functionality C interface Control backtracking C Function void PrologEnableEpilog void void
210. 57 Term igsList Test f r list lt e bes Seka eB ea a BR RES ee DS 758 TermIsNil Test for empty list aoaaa a 760 TermIsUniversal Test for structure oaoa a a 761 Term isVar 0 Test for yarria ble ere od ecs ee ei a eee Da O a 763 TermMakeAtom Generate a Prolog atom aooo a a a 764 TermMakeCompound Generate a Prolog structure o oo aaa 765 TermMakeFloat Generate a Prolog floating point number 767 TermMakeFunctor Generate a Prolog structure 768 TermMakeInteger Generate a Prolog integer 770 TermMakeList Generate a Prolog list 2 00 2 771 xvi TermMakeNil Generate an empty list 0 0 TermMakeUniversal Generate a Prolog structure TermMakeVar Generate a Prolog variable TermOpenList Generate a Prolog list 22 24 TermType Classify term gc bee eRe RE RED EEE ES TermUnity Unity terme on dea ek Pa ee kk ee ew Ee we ES TermUnifyAtom Unify term with atom TermUnifyCompound Unify term with structure TermUnifyFloat Unify with floating point number TermUnifyFunctor Unify term with structure TermUnifyInteger Unify term with integer 0 0 TemlmifyLiet Unity term with lst so se ic ee dea enaa TermUnifyNil Q Unify term with th
211. Atom index 3 fails Arguments Atom Atom String Atom Position Integer 0 lt Position lt Length of Atom Exceptions instantiation_error The argument Atom or String must not be a variable but a variable was specified type_error atom The argument Atom or String must be an atom but is a term of another type type_error integer The argument Position must be a variable or an integer but is a term of another type Example The string here is contained in the first argument and starts at position 3 Backtracking does not take place user index xxherexxherexx here X lt ENTER gt X 3 lt ENTER gt no Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Reference Manual 304 IF Prolog V5 3 index 3 Predicate String processing See also atom_concat 3 atom_part 4 atom_prefix 3 atom_suffix 3 getchar 3 sub_atom 5 atom_split 3 IF Prolog V5 3 305 Reference Manual Execution control Directive init 1 initialization 1 Initialization goal init Goal init Goal initialization Goal initialization Goal The directives init 1 and initialization 1 tell IF Prolog to execute Goal after a Prolog text has been loaded The directives init 1 and initialization 1 may not occur in the module interface If there is more than one init 1 or initialization 1 directive in a
212. C Function TermUnify Universal Unify term with structure include cpred h BOOLEAN TermUnifyUniversal TERM Term STRING Functor ARITY Arity TERM Args The function TermUnifyUniversal unifies the term Term with the structure with the name Functor and the arity Arity and the arguments Args If a term in Args is NULL a new Prolog variable is used instead If unification is successful the function returns TRUE otherwise it returns FALSE Arguments Term Term variable Functor Character string name of the structure Arity Integer 0 lt Arity lt 127 Args Vector with Arity term variables NULL Exceptions The following errors cause IF Prolog to be exited implementation_error Arity arity out of range The argument Arity is not within the range 0 127 implementation_error TermUnifyUniversal out of memory The function TermUnifyUniversal could not be executed successfully due to a lack of memory Hints The call of TermUnifyUniversal Term Functor Arity Args is except for optimization identical to TermUnify Term TermMakeUniversal Functor Arity Args Reference Manual 790 IF Prolog V5 3 Term Unify Universal C Function Active C interface Example The following simple C function realizes a predicate mk_assignment 3 which makes a term of the form Term1 Term2 of two given arguments include cpred h BOOLEAN mk_assignment_3 void k mk_assignment Term1
213. C Function TermlsList Test for list include cpred h BOOLEAN TermIsList TERM Term TERM Head TERM Tail The function TermIsList tests whether the term Term is a non empty list If it is Head is initialized with the list head and Tail with the list tail provided that Tail and Head are not NULL and the function returns TRUE If the term is the empty list the function returns FALSE If the term is not a list the function sets the error context and returns FALSE Arguments Term Term variable Head Tail Pointer to term variables Exceptions instantiation_error The argument Term must not be a variable but a variable was specified type_error list The argument Term must be a list but is a term of another type Example The following simple C function realizes a predicate list_sum 2 which sums up all elements of a list of integers include cpred h BOOLEAN list_sum_2 void list_sum List Sum long value total TERM head tail tail PrologArg 1 while TermIsList tail amp head amp tail Reference Manual 758 IF Prolog V5 3 TermlsList C Function Active C interface amp amp TermIsInteger head amp value total value return ErrorContextIsSet amp amp TermUnifyInteger PrologArg 2 total void Cboot void CPRIM list_sum 2 list_sum_2 See also TermMakelList IF Prolog V5 3 759 Reference Manual
214. Connect a socket socket_connect Socket Addr The predicate socket_connect 2 connects the socket Socket The argument Addr specifies the address to which the socket is to be connected The address for internet domain socket must have the form Host Port where Host is either the atom representing the hostname or a single quoted atom or a list of three integers both representing the IP Address of the remote machine Port is the port number of the remote machine The address for unix domain socket must be an atom Filename The file must exist and be a socket i e must have been created previously by the server process with socket_bind 2 A stream socket may be connected only once A datagram socket can be disconnected by specifying Addr 0 Arguments Socket Socket system defined term Addr Structure Host Port or atom Filename Host Atom or IntegerList Port Integer Filename Atom Exceptions instantiation_error The argument Socket or Addr must not be a variable but a variable was specified type_error socket The argument Socket must be a socket supplied by socket 3 but is a term of another type domain_error socket The argument Socket must be a currently open socket supplied by socket 3 type_error host port The argument Addr must be a structure of the form Host Port but is a term of another type type_error atom The argument Host must be an atom but is a term of another type type_error
215. Cshutdown void The function Cshutdown is called automatically on IF Prolog shutdown inside the EndProlog function It is used to call the user defined C code on IF Prolog shutdown e g releasing user allocated resources Hints An empty Cshutdown function supplied by he system is used if the user did not define an own Cshutdown function You can find it in the file Cboot c See also Cboot EndProlog IF Prolog V5 3 695 Reference Manual Device driver interface C Function DeviceCreate Register device driver include device h void DeviceCreate t_device Device The function DeviceCreate declares the new device driver to IF Prolog The argument Device is a pointer to the structure of type t_device which contains all the properties of the new device driver This data must be created and initialized by the user It must not be modified after being registered at startup of IF Prolog The functions of the device driver are called by IF Prolog mostly as result of some predicate calls e g open 3 4 Arguments Device Pointer to structure of the type t_device Hints The data structures and functions of device drivers are described in the F Prolog User s Guide 2 The function DeviceCreate should be called from the C function Cboot which is executed at startup of IF Prolog See also Cboot open 3 4 device_control 2 stream_control 2 Reference Ma
216. Drivename The predicate windows_chdrive 1 changes the current drive to Drivename An error occurs if the drive does not exist Arguments Drivename Letter name of a drive Exceptions instantiation_error The argument Drivename must not be a variable but a variable was specified type_error character The argument Drivename must be a character but is a term of another type domain_error drive_name The value of the argument Drivename is not a valid drive character system_error chdrive_failed The operating system did not allow to change to the requested drive Hints To write code that should run under diverse operating systems you can use the predicate system_name 1 to determine the current operating system On operating systems that do not support the concept of drives this predicate has no effect Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1A The predicate windows_chdrive 1 is new Windows This predicate is only available under Windows and OS 2 operating systems See also windows_getdrive 1 system_name 1 chdir 2 getewd 2 IF Prolog V5 3 599 Reference Manual Operating system Predicate windows_getdrive 1 Query drive windows_getdrive Drivename The predicate windows_getdrive 1 retrieves the name of the current drive and unifies it with Drivename Argu
217. E otherwise it returns FALSE Arguments Term Term variable Functor Character string name of the structure Arity Integer 0 lt Arity lt 127 Arity pointers to term variables or NULL Exceptions The following errors cause IF Prolog to be exited implementation_error Arity arity out of range The argument Arity is not within the range 0 127 implementation_error TermUnifyCompound out of memory The function TermUnifyCompound could not be executed successfully due to a lack of memory Hints The call of TermUnifyCompound Term Functor Arity is except for optimization identical to TermUnify Term TermMakeCompound Functor Arity Reference Manual 782 IF Prolog V5 3 Term UnifyCompound C Function Active C interface Example The following simple C function realizes a predicate mk_indicator 3 which makes a predicate indicator from given name and arity include cpred h BOOLEAN mk_indicator_3 void xx mk_indicator Functor Arity Indicator STRING string long value TERM functor PrologArg 1 TERM arity PrologArg 2 return TermIsAtom functor amp string amp amp TermIsInteger arity amp value amp amp TermUnifyCompound PrologArg 3 2 functor arity void Cboot void CPRIM mk_indicator 3 mk_indicator_3 See also TermUnifyFunctor TermUnifyUniversal TermUnify TermMakeCompound IF Prolog V5 3 783 Reference Manual Active C
218. Exceptions instantiation_error The argument Filename must not be a variable but a variable was specified type_error atom The argument Filename must be an atom but is a term of another type domain_error file_name The value of the argument Filename is not a valid name for a file permission_error open source_sink The argument Filename specifies a file or a different I O medium that cannot be opened system_error write system_error close system_error flush_output system_error interrupted The indicated error was reported by the operating system when writing on the output stream Filename Hints Files created with save_module 1 can be loaded by calling IF Prolog with the param eter l Filename or by using load 1 during a Prolog session Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso IF Prolog V5 3 465 Reference Manual Module concept Predicate save_module 1 See also load 1 unload 1 compile 1 save_system 1 Reference Manual 466 IF Prolog V5 3 save_runtime 1 Predicate Database Save system status for creating applications save_runtime Filename The predicate save_runtime 1 saves all static information concerning the current system status in the file Filename If Filename does not contain the extension pst the extension is appended and the resultant filename Filena
219. F Prolog V5 3 create_array 2 Predicate Term classification Create an array create_array Array Dimension The predicate create_array 2 creates an array of Dimension terms and unifies it with Array Each element of the array is initialized to integer term 0 zero Arguments Array Array system defined term Dimension Positive integer Exceptions instantiation_error The argument Dimension must not be a variable but a variable was specified type_error array The argument Array must be a variable or an array but is a term of another type type_error integer The argument Dimension must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer domain_error greater_than_zero The argument Dimension must be an integer greater than zero but is negative or equal to zero Furthermore if an arithmetic expression is specified for the argument Dimension all the exceptions for is 2 can occur Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1A The predicate create_array 2 is new See also array 1 2 get_array 3 set_array 3 IF Prolog V5 3 171 Reference Manual Stream processing Predicate current _alias 2 Query aliases of input output streams current_alias Alias Stream
220. Force the current subgoal to fail fail f The fail O command forces the current subgoal to fail the debugger branches to the FAIL FAILMATCH or FAILBODY port in the current box and stops there Exceptions domain_error arity The command fail 0 was called with an incorrect number of parameters See also error 2 exit 0 Reference Manual 644 IF Prolog V5 3 fast_skip 0 1 Debugger command Command interface Accelerate execution to exit of a subsequent subgoal fast_skip fs fast_skip Number fs Number The fast_skip 0 1 command resumes the debugger session the debugger stops at the exit EXIT of the current Number th subgoal starting at the current subgoal and switches to interactive mode If Number is larger than the number of the remaining subgoals in the current clause the debugger is positioned after the last subgoal of the current clause it stops at the next subgoal of the parent clause If the execution of the current Number th subgoal fails the debugger stops at the exit FAIL ERROR of the subgoal involved The debugger does not metainterpret the subgoals they are called directly instead This means that breakpoints in subgoals are ignored The command fast_skip 0 is equivalent to the command fast_skip 0 Arguments Number Integer or integer expression Number gt 0 Exceptions instantiation_error The argument Number or a subterm must not be a variable but a
221. G Format Initialize Prolog passive C interface C Function BOOLEAN EndProlog void Generate a Prolog structure Generate a Prolog variable Functionality Register device driver Flush Prolog output buffer Query stream mode Functionality Formatted output of Prolog terms and C data objects Determine length of formatted output Formatted output of Prolog terms and C data objects Formatted output of Prolog terms and C data objects Functionality Release memory space used by IF Prolog IF Prolog V5 3 687 Reference Manual Overview by functionality C interface BOOLEAN InitProlog int Number STRING Argument Vector FILE Input FILE Output FILE Error Memory management C Function void TermCollect TERMCONTEXT context void TermCollectSequence TERM CONTEXT context size_t N TERM TermList TERMCONTEXT TermContext void Prepare Prolog terms C Function STRING ParseError int Number BOOLEAN ParseProlog STRING GoalAtom t_parse_context Context MODULE PrologModule STRING Name Passive Prolog terms C Function t_query QueryCreate MODULE Module TERM Goal TERM VarList void QueryDispose t_query Query t_cursor QueryOpen t_query Query Initialize IF Prolog and define the standard media Functionality Release term variables Release term variables Current set of term variables Functionality Assignment of syntax erro
222. G Module STRING Functor ARITY Arity CPRIMFUN Function The function MCPRIM is used to incorporate the predicate Functor Arity into IF Prolog The predicate is implemented by the simple C function Function A simple function is deterministic i e does not allow backtracking The predicate is assigned to the module Module Arguments Module Character string Functor Character string Arity Integer 0 lt Arity lt 127 Function C Function Hints The function MCPRIM should be called from the C function Cboot which is executed at startup of IF Prolog A module cannot be defined by simply adding C functions The predicates can only be used as soon as the module interface is created See also Cboot CPRED CPRIM MCPRED IF Prolog V5 3 709 Reference Manual Passive C interface C Function outputlen Determine length of formatted output include cpro h size_t outputlen STRING Format The function outputlen returns the number of characters that would be printed at the formatted output of the arguments with the format Format An argument may be either a Prolog term or a normal C data object The arguments are printed in accordance with the formatting Arguments Format Character string format specification see write_formatted 2 3 Prolog terms or C data objects in accordance with Format See also fprintt printt sprintt write formatted 2 3 Refe
223. Goal must have the syntactical structure of a Prolog goal existence_error procedure In executing Goal a predicate was to be activated which is not defined and the Prolog flag unknown has the value error type_error atom The argument Goal or a subgoal has been qualified by means of 2 or 2 with a term that is not an atom existence_error module The argument Goal or a subgoal is qualified by means of 2 or 2 with an atom that does not name an existing module domain_error arity The command call1 1 was called with an incorrect number of parameters See also abort 0 break 0 call 1 set_prolog_flag 2 Reference Manual 638 IF Prolog V5 3 continue 0 Debugger command Command interface Continue to next breakpoint continue c The continue 0 command resumes the debugging session and the debugger stops at the next breakpoint All implicit breakpoints except ERROR are deactivated Exceptions domain_error arity The command continue 0O was called with an incorrect number of parameters See also step 0 skip 0 1 nonstop 0 fast_skip 0 1 IF Prolog V5 3 639 Reference Manual Command interface Debugger command deactivate_stop 0 1 Deactivate breakpoint temporarily deactivate_stop ds deactivate_stop Numbers ds Numbers The deactivate_stop 1 command deactivates the explicit breakpoints specified using the Numbers argument If Numbers is omitted all current expl
224. IF Prolog V5 3 Reference Manual Siemens AG Austria Is there anything you would like to tell us about this manual Please send us your comments Siemens AG Austria PSE KB B3 Gudrunstrasse 11 A 1100 Vienna Austria Fax 43 1 1707 56992 email prologQ siemens at The information in this document is subject to change and does not represent a commitment on the part of Siemens AG Austria The software described in this document is furnished under a license agreement The software may be used or copied only in accordance with the terms of the agreement UNIX is a registered trademark in the United States and other countries licensed exclusively through X Open Company Limited X Open and the X device are trademarks of X Open Company Ltd Copyright Siemens AG Austria 1999 All rights reserved The reproduction transmission translation or exploitation of this document or its contents is not permitted without express written authority Offenders will be liable for damages Delivery subject to availability right of technical modifications reserved Contents Contents Introduction Reference section on commands link proleg Recaniguse Prolog sa eca s ce eed ede ewe a Se ES procup Invoke the Prolog compiler 14445 ocs ac 24 4a HOR ES procref Invoke the Prolog definition referencer prolog Start of the Prolog Syste e sosoo s kos e ew eS Ow eS proopt Invoke the Prolog optimizer 22
225. ISO standard for Prolog Compatibility V5 0B ISO conformance exception permission_error input text_stream is gen erated instead of permission_error input binary_stream when the stream is not a binary stream See also peek_byte 1 2 get_char 1 2 get_code 1 2 IF Prolog V5 3 267 Reference Manual Elementary input output Predicate get_char 1 2 Input a character get_char Character get_char Stream Character The predicate get_char 1 reads the next character from the current input stream cur rent_input and unifies Character with the character read in The predicate get_char 2 acts in the same way for the specified input stream Stream If the end of the input stream has been reached Character is unified with the atom end_ of_file The predicates can be applied only for text streams see open 3 4 Arguments Stream Stream system defined term or alias atom Character Character or end_of_file Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error input stream The argument Stre
226. ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1A The argument Year is represented with 4 digits See also is 2 IF Prolog V5 3 333 Reference Manual String processing Predicate lower_upper 2 Convert between lowercase and uppercase letters lower_upper Lowercase Uppercase lower_upper Lowercase Uppercase The predicate lower_upper 2 converts lowercase letters in atoms into uppercase letters and vice versa Arguments Lowercase Atom Uppercase Atom Exceptions instantiation_error The argument Lowercase or Uppercase must not be a variable but a variable was specified type_error atom The argument Lowercase or Uppercase must be an atom but is a term of another type Example The atom small is converted into SMALL user lower_upper small X lt ENTER gt X SMALL lt ENTER gt yes Only the remaining uppercase letters are converted user lower_upper X bIG lt ENTER gt x big lt ENTER gt yes Special characters are not affected Reference Manual 334 IF Prolog V5 3 lower_upper 2 Predicate String processing user lower_upper S i_am_UPPER_CASE lt ENTER gt S i_am_upper_case lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See als
227. Input output for terms Output a term write_canonical Term write_canonical Stream Term The predicate write_canonical 1 writes Term to the current output stream in a format that allows the term to be read in again The predicate write_canonical 2 acts in the same way as write_canonical 1 but writes to the specified output stream Stream Operator notation is not used in the output and atoms containing special characters are always quoted All floating point numbers that appear in Term are output with the highest possible precision Arguments Term Term Stream Stream system defined term or alias atom Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error output stream The argument Stream is not a stream which has been opened for output open mode write or append system_error write system_error close system_error flush_output system_error interrupted The indicated error was reported by the operating system when writing on the output stream Stream IF Prolog V5 3 605 Reference Manu
228. N PrologFetch t_cursor ActGoal t_cursor PrologOpen MODULE Module TERM Goal TERM VarList Analyze term C Function TERM TermArg ARITY Argno TERM Term Functionality Deactivate the current Prolog goal Query error Find solutions for a goal Create current Prolog goal Functionality Access structure arguments Overview by functionality C interface TERMTYPE TermDecompose TERM Term TERMINFO Info TERMTYPE TermType TERM Term Test Prolog terms C Function BOOLEAN TermIsAtom TERM Term STRING Name BOOLEAN TermIsCompound TERM Term STRING Functor ARITY Arity BOOLEAN TermIsFloat TERM Term double Value BOOLEAN TermIsFloatExpression TERM Term double Value BOOLEAN TermIsFunctor TERM Term STRING Functor ARITY Arity BOOLEAN TermIsInteger TERM Term long Value BOOLEAN TermIsIntegerExpression TERM Term long Value BOOLEAN TermIsList TERM Term TERM Head TERM Tail BOOLEAN TermIsNil TERM Term BOOLEAN TermIsUniversal TERM Term STRING Functor ARITY Arity TERM Args BOOLEAN TermlIsVar TERM Term Classify term Classify term Functionality Test for atom Test for structure Test for floating point number Test for floating point expression Test for structure Test for integer Test for integer expression Test for list Test for empty list Test for structure Test for variable Reference Manual 684 IF Prolog V
229. NTER gt Y 35 lt ENTER gt yes Standard This predicate complies with the definition of the ISO standard for Prolog See also atom 1 atomic 1 compound 1 cyclic 1 float 1 ground 1 integer 1 number 1 rational 1 var 1 IF Prolog V5 3 367 Reference Manual Execution control Language construct not 1 Negation through failure not Goal not Goal The language construct not 1 calls Goal and fails if Goal succeeds Otherwise not 1 succeeds Arguments Goal Goal Exceptions instantiation_error The argument Goal must not be a variable but a variable was specified type_error callable The argument Goal must have the syntactical structure of a Prolog goal existence_error procedure In executing Goal a predicate was to be activated which is not defined and the Prolog flag unknown has the value error type_error atom The argument Goal or a subgoal has been qualified by means of 2 or 2 with a term that is not an atom existence_error module The argument Goal or a subgoal is qualified by means of 2 or 2 with an atom that does not name an existing module Hints The atom not is defined as a prefix operator The language construct not 1 is identical to 1 The language construct not 1 is not a predicate so it cannot be redefined The pred icates current_predicate 1 and current_visible 2 do not indicate language con structs Explicit module qualification with 2 or 2 i
230. Name Atom Exceptions instantiation_error The argument Name must not be a variable but a variable was specified type_error atom The argument Name must be an atom but is a term of another type Hints Global variables are always assigned to a module they can be neither exported nor imported In operations with global variables therefore only those global variables defined in the calling module or in the specified Module are taken into account Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also current_global 1 get_global 2 pop_global 2 push_global 2 set_global 2 IF Prolog V5 3 595 Reference Manual System information Predicate user_parameters 1 Query user parameters from IF Prolog call user_parameters ParameterList The predicate user_parameters 1 unifies ParameterList with a list of all user parameters which were specified on calling IF Prolog User parameters are all the call parameters which are not system parameters see system_ parameters 1 or which are entered on the command line after the special system parameter Arguments ParameterList List of atoms Exceptions type_error list The argument ParameterList must be a variable or a list but is a term of another type type_error atom An element of ParameterList must be a variable or an atom but is a term of another
231. Numbers must be a positive integer but is negative existence_error stop The argument Numbers does not specify an existing breakpoint domain_error arity The command activate_stop 0 1 was called with an incorrect number of param eters Furthermore if an arithmetic expression is specified for the argument Numbers all the exceptions for is 2 can occur Hints Breakpoints can be deactivated with the deactivate_stop 0 1 command Reference Manual 632 IF Prolog V5 3 activate_stop 0 1 Debugger command Command interface See also deactivate_stop 0 1 remove_stop 0 1 stop1 2 4 stop_interactive 1 2 4 view_stops 0 IF Prolog V5 3 633 Reference Manual Command interface Debugger command back_clause 0 Branch back to clause head back_clause bc The back_clause 0 command is used to branch back to the head of the current clause TRYMATCH port If the command is entered at a clause head the debugger branches back to the clause head of the ancestor clause If no ancestor clause exists the debugger reports an error The debugger stops at the goal of the back_clause 0 command Because execution of this command is equivalent to resetting the system to a previous state variable instantiations may be undone Exceptions existence_error clause The command back_clause 0 cannot be executed at this point in the proof tree because the current predicate does not possess any clauses existence_error previo
232. P L P g L P E L P G L P L Integer or integer expression 1000 lt L lt 1000 P Integer or integer expression 0 lt P lt 100 IF Prolog V5 3 253 Reference Manual Input output for terms Predicate float _format 2 Exceptions instantiation_error The argument FormatNew or a subterm must not be a variable but a variable was specified type_error compound The argument FormatNew must be a structure but is a term of another type domain_error float_format The value of the argument FormatNew is not a valid format specification type_error integer The argument L or P in FormatNew must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer type_error compound The argument FormatOld must be a variable or a structure but is a term of another type domain_error float_format The value of the argument FormatOld is not a valid format specification type_error integer The argument L or P in FormatOld must be a variable or an integer but is a term of another type Furthermore if an arithmetic expression is specified for the argument L or P in For matNew all the exceptions for is 2 can occur Hints The output format set with float_format 2 for floating point numbers affects the out put predicates for terms write 1 2 and possibly also write_term 2 3 and conversion predicates e g write_atom 2 The output pre
233. Prolog V5 3 Predicates Overview by functionality predicate_mode Predicate Before After predicate_type Predicate Type private PredicateList reexport Module reexport Module PredicateList Execution control Goall Goal2 ConditionGoal gt ThenGoal ConditionGoal gt ThenGoal ElseGoal Goall Goal2 Goal abort bagof Term Goal TermList break call Goal call Name ArgList fail findall Term Goal TermList for Start Counter End for Start Counter End halt halt ExitStatus init Goal initialization Goal not Goal once Goal program repeat setof Term Goal TermList true Contexts exceptions alarm Seconds Query and set the exception mode of a predicate Query predicate type Declare predicates as private Reexport predicates Reexport predicates Disable backtracking Conjunction of goals IF THEN conjunction of goals IF THEN ELSE conjunction of goals Disjunction of goals Negation through failure Return to the toplevel loop of IF Prolog Find selected solutions of a goal Generate a new input loop Call a goal Call a goal Initiate backtracking Find all solutions of a goal Check range Generate a sequence of integers Terminate Prolog Terminate Prolog and set exitstatus Initialization goal Initialization goal Negation through failure Activate a goal once only Automat
234. R gt write hello lt ENTER gt xxx EX C EP TION system_error gt gt gt error interrupt gt gt gt signal interrupt gt gt gt interrupted system unix_kill 3443 interrupt gt gt gt goal true no user unix_kill 9999 0 lt ENTER gt no See also the example in the section Process management and communication in the IF Prolog User s Guide 2 Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also unix_fork 1 unix_wait 1 2 unix_getpid 1 signal_control 2 signal_handler 3 IF Prolog V5 3 589 Reference Manual Stream processing Predicate unix_make_pipe 1 Create a pipe unix_make_pipe Pipename The predicate unix_make_pipe 1 creates a pipe and unifies Pipename with a medium name that can be directly specified as the first argument of open 3 4 unix_fork 1 exec 1 2 Arguments Pipename Name of the pipe medium Exceptions type_error variable The argument Pipename must be a variable but is a term of another type system_error could_not_create_pipe The operating system was not able to create a pipe This is often due to resource bottlenecks or limitations in the operating system Hints Pipes are normally used for process communication They are inherited by child pro cesses If a pipe that is created with unix_make_pipe 1 is opened in IF Prolog with op
235. Reference Manual System information Predicate set_prolog_flag 2 backtrace 10 The maximal length of the backtrace list The list is created when an exception has been raised and con tains the calling sequence of goals that has led to the exception The elements of the list are predicate in dicators Functor Arity Goals that have been re moved due to tail recursion optimization normally the last subgoal in a clause body are not included in the list double_quotes codes Characters inside double quotes are to be inter preted as a list of character codes when reading a term e g with read 1 2 chars Characters inside double quotes are to be inter preted as a list of characters when reading a term e g with read 1 2 atom Characters inside double quotes are to be inter preted as an atom when reading a term e g with read 1 2 extended_syntax on Cyclic terms can be entered using the notation Variable Term When reading such a cyclic term Variable is unified with Term The above notation is also used by output of cyclic terms see 2 off Cyclic terms can be entered in the above notation but Variable is not unified with Term nested_comments off Nested comments are not allowed in a Prolog text Begin of a comment inside a comment is ignored which normally leads to a syntax error on Nested comments are accepted in a Prolog text write_depth 10 Maximal depth of terms output in the Prolog top
236. TC Universal Time Coordinated Greenwich Mean Time and local standard time LST resp an alternate time zone and if an alternate time zone ATZ is used daylight savings time Arguments Time Integer TimeZone Integer difference in seconds between UTC and LST AlternateZone Integer difference in seconds between UTC and ATZ DaylightSaving Atom on off Exceptions instantiation_error The argument Time must not be a variable but a variable was specified type_error integer The argument Time must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer type_error integer The argument TimeZone or AlternateZone must be a variable or an integer but is a term of another type type_error atom The argument DaylightSaving must be an atom but is a term of another type Furthermore if an arithmetic expression is specified for the argument Time all the exceptions for is 2 can occur Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1B The predicates timezone 4 are new Reference Manual 570 IF Prolog V5 3 timezone 4 Predicate Operating System See also is 2 local_time 9 IF Prolog V5 3 571 Reference Manual Stream processing Predicate told 0 Reset current output stream told The p
237. TER gt write effective nl lt ENTER gt noteffective yes Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also outtab 1 2 write 1 2 put_char 1 2 Reference Manual 564 IF Prolog V5 3 tell 1 Predicate Stream processing Set current output stream tell Stream The predicate te11 1 makes Stream the current output stream If the argument Stream is not an input output stream and not a defined alias it must be an atom A file of this name is then opened for writing If this succeeds the name is simultaneously registered as an alias for the opened output stream and the stream becomes the current output stream Arguments Stream Stream system defined term alias atom or filename atom Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream domain_error file_name The value of the argument Stream is not a valid name for a file permission_error output stream The argument Stream is not a stream which has been opened for output open mode write or append permission_error open source_sink T
238. The argument List or a subterm must not be a variable but a variable was specified type_error list The argument List must be a list but is a term of another type type_error character An element of List must be a character but is a term of a another type type_error atom The argument Atom must be an atom but is a term of another type Example user atom_chars atom X lt ENTER gt X a t o m lt ENTER gt yes user atom_chars X a t o m lt ENTER gt IF Prolog V5 3 99 Reference Manual Term conversion Predicate atom_chars 2 X atom lt ENTER gt yes List may be partially uninstantiated if Atom is instantiated user atom_chars abcd _ X c Y lt ENTER gt X b Y d lt ENTER gt yes Standard This predicate complies with the definition of the ISO standard for Prolog See also number chars 2 atom_codes 2 Reference Manual 100 IF Prolog V5 3 atom_codes 2 Predicate Term conversion Convert between an atom and individual character codes atom_codes Atom List atom_codes Atom List The predicate atom_codes 2 establishes the relationship between an atom and the list com prising of the individual character codes of the atom A distinction is made between two cases 1 Atom is instantiated List must be either a variable or a list of variables or character codes The predicate atom_codes 2 creates the list of character codes of Atom and unifi
239. The argument Position must be a positive integer but is negative type_error compound The argument Structure must be a structure but is a term of another type Furthermore if an arithmetic expression is specified for the argument Position all the exceptions for is 2 can occur Example user arg 2 f x y z T lt ENTER gt T y lt ENTER gt yes user S struc A B lt ENTER gt write S nl lt ENTER gt Reference Manual 80 IF Prolog V5 3 arg 3 Predicate Term conversion arg 1 S one lt ENTER gt write S nl lt ENTER gt struc _69 _70 struc one _70 S struc one _70 A one B _70 lt ENTER gt yes Standard This predicate complies with the definition of the ISO standard for Prolog The use of arithmetic expressions in the argument Position is not allowed in the ISO standard for Prolog In the ISO compatibility mode see Prolog flag iso therefore no arithmetic expressions may be used as arguments for this predicate Instead an evaluation must be programmed explicitly with the help of is 2 if necessary See also imnetorss 2 IF Prolog V5 3 81 Reference Manual Term classification Predicate array 1 Test for array array TestTerm The predicate array 1 succeeds if TestTerm is an array term otherwise it fails Arguments Test Term Term Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO
240. The argument Term must be an atom or a structure but is a term of another type domain_error compound The argument Term is a structure but its functor or arity are not correct The following error causes IF Prolog to be exited implementation_error Arity arity out of range The argument Arity is not within the range 0 127 Example The following simple C function realizes a predicate assignment 1 which checks if its argument is a term of the form Term1l Term2 include cpred h BOOLEAN assignment_1 void Reference Manual 754 IF Prolog V5 3 TermlsFunctor C Function Active C interface xx assignment Term return TermIsFunctor PrologArg 1 2 void Cboot void CPRIM assignment 1 assignment_1 See also TermIsCompound TermIsUniversal TermMakeFunctor IF Prolog V5 3 755 Reference Manual Active C interface C Function TermlsInteger Test for integer include cpred h BOOLEAN TermIsInteger TERM Term long Value The function TermIsInteger tests whether the term Term is an integer within the range of values for a C variable of the type signed long If it is the function stores the value of the number in Value and returns TRUE Otherwise it sets the error context and returns FALSE In this case Value is not changed Arguments Term Term variable Value Pointer to an integer number Exceptions instantiation_error The
241. V5 3 manual 0 1 Predicate System information Example user manual true lt ENTER gt Name true 0 Goal which is always true Syntax true Description The language construct true 0O succeeds exactly once Hints The language construct true O is not a predicate so it cannot be redefined The predicates current_predicate 1 and current_visible 2 do not indicate language constructs Explicit module qualification with 2 or 2 is not permitted for language constructs with the exception of call 1 Standard This language construct complies with the definition of the ISO standard for Prolog See also fail 0 yes user manual garbona lt ENTER gt yes Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also help 0 1 current_visible 2 import 1 2 IF Prolog V5 3 337 Reference Manual String processing Predicate match 2 3 Pattern matching match Mask Atom match Mask Atom Replacements The predicates match 2 3 carry out pattern matching The following special pattern characters can be used to form the mask At the place where this character stands in Mask any single character may occur in Atom At the place where this character stands in Mask any character string or an empty string may occur in Atom other All other characters
242. V5 3 365 Reference Manual Database Directive nonotify 0 Do not output load message nonotify The directive nonotify 0 disables the output of a message when the Prolog text is read in with consult 1 reconsult 1 or compile 1 The effect is local in contrast to the Prolog flag consult i e applies only for the Prolog text containing the directive and files included from this text Exceptions Errors in directives are detected with consult 1 reconsult 1 or compile 1 No exceptions are generated Instead only error messages are output on the current error output stream Hints Directives are evaluated during consultation see consult 1 reconsult 1 or compi lation see compile 1 procmp command Standard The directive nonotify 0 is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also consult 1 ensure_loaded 1 include 1 compile 1 set_prolog_flag 2 Reference Manual 366 IF Prolog V5 3 nonvar 1 Predicate Term classification Test for instantiation nonvar TestTerm The predicate nonvar 1 succeeds if TestTerm is not a variable otherwise it fails Arguments Test Term Term Example user nonvar a X Y lt ENTER gt X _68 Y _69 lt ENTER gt yes user nonvar three lt ENTER gt yes user nonvar X lt ENTER gt no user Y is 35 nonvar Y lt E
243. _error callable The argument Goal must have the syntactical structure of a Prolog goal existence_error procedure In executing Goal a predicate was to be activated which is not defined and the Prolog flag unknown has the value error type_error atom The argument Goal or a subgoal has been qualified by means of 2 or 2 with a term that is not an atom existence_error module The argument Goal or a subgoal is qualified by means of 2 or 2 with an atom that does not name an existing module Hints The language construct call 1 is not a predicate so it cannot be redefined The predicates current_predicate 1 and current_visible 2 do not indicate language constructs Explicit module qualification with 2 is not permitted for this language construct The predicates activated in the goal must be visible in the calling module or in the specified Module unless the 2 qualification is used for such a predicate to indicate explicitly the module in which this predicate is visible IF Prolog V5 3 125 Reference Manual Execution control Language construct call 1 The predicates activated in the goal are normally executed in the context of the module in which they are defined This does not apply to metapredicates which are executed in the context of the calling module or the specified Module unless the 2 qualification is used for a metapredicate to indicate explicitly the module context in which this predicate is to be execu
244. _length Atom Length The predicate byte_length 2 unifies Length with the number of bytes in the atom Atom The predicate is equivalent to atom_length 2 if IF Prolog has not been configured with multiple octet characters or the current language is ascii Arguments Atom Atom Length Integer Exceptions instantiation_error The argument Atom must not be a variable but a variable was specified type_error atom The argument Atom must be an atom but is a term of another type type_error integer The argument Length must be a variable or an integer but is a term of another type domain_error not_less_than_zero The argument Length must be a positive integer but is negative Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also atom _length 2 Reference Manual 124 IF Prolog V5 3 call 1 Language construct Execution control Call a goal call Goal Module The language construct cal1 1 calls the goal Goal in the calling module or in the specified Module and succeeds if Goal succeeds By backtracking Goal can return several results If Goal is a composite goal and contains a cut 0 then this cut will have no effect beyond call 1 Arguments Goal Goal Exceptions instantiation_error The argument Goal must not be a variable but a variable was specified type
245. _mode 3 See also abolish 1 dynamic 1 modify_mode 3 Reference Manual 408 IF Prolog V5 3 predicate_type 2 Predicate Database Query predicate type predicate_type Predicate Type Module The predicate predicate_type 2 determines the type of the Predicate Type is unified with an atom that represents the type of the predicate Identification of the predicate is based on its visibility in the calling module or in the specified Module The following types are possible Type Explanation builtin The predicate is defined and is either a built in predicate or a C language predicate compiled The predicate is a user defined and compiled Prolog predicate imported The predicate is an imported predicate that is defined in another module linear The predicate is a user defined but uncompiled Prolog predicate or was declared as dynamic control The argument is a language construct not a predicate undefined Otherwise Arguments Predicate Structure of the form Functor Arity Type Atom Functor Atom Arity Integer 0 lt Arity lt 127 Exceptions instantiation_error The argument Predicate or a subterm must not be a variable but a variable was specified type_error predicate_indicator The argument Predicate must be a predicate indicator i e a structure with the format Functor Arity but is a term of another type type_error atom The name of the predicate Predicate must be an atom
246. a normal structure X is 544 273 Reference Manual 796 IF Prolog V5 3 Terms Prolog Syntax Blanks not functioning as delimiters In strings delimited by single or double quotes blanks are part of the string and thus do not function as delimiters Disabling the The return key retains its delimiter function even in strings enclosed in single or double quotes unless it is disabled by the backslash The disabled end of line character is not included in atoms or character lists Without the preceding backslash lt will result in a syntax violation if used in these strings gt abcde fgh corresponds to abcdefgh Making inputs easier to read Delimiters can be used to make Prolog text easier to read Delimiters tabs blanks com ments new line characters may be inserted between any lexical elements except between the functor and opening parenthesis in normal structures as otherwise the functor would be interpreted as an operator Examples of dividing into lexical elements Prolog can recognize lexical elements in the following cases among others 3is 1 2 The characters i and each indicate the end of the preceding number blanks are not required However there must be at least one blank between is and 1 as Prolog would otherwise interpret the input as the atom is1 X Blanks are not required 10 2 3 The slash indicates the end
247. a structure into a list or a list into a structure A distinction can be made between two cases 1 Structure is instantiated In this case List must be a variable or a list A list is formed from Structure in which the first element is the functor of Structure and subsequent elements are the arguments of Structure The resultant list is unified with List If Structure is a constant then the constructed list contains only this constant Structure is uninstantiated In this case List must have at least one element If List contains precisely one element this must be a constant and Structure is unified with this element If List consists of more than one element the first element must be an atom and a structure is constructed from List The structure has this first element as the functor and the remaining elements of List as arguments Structure is then unified with this structure Arguments Structure Structure constant List List regular and not empty Exceptions type_error list The argument List must be a variable or a list but is a term of another type instantiation_error The argument List must not be a variable but a variable was specified instantiation_error The first element of List must not be a variable but a variable was specified type_error atom List is a list whose head is neither an atom nor a variable and whose tail is not the empty list type_error atomic List is a list whose head is a compound te
248. a variable a character or the special atom end_ of_file but is a term of another type or an invalid atom IF Prolog V5 3 281 Reference Manual Elementary input output Predicate get _until 3 4 domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error input stream The argument Stream is not a stream which has been opened for input open mode read permission_error past_end_of_stream The open option eof_action error was set for the input stream Stream and the end of the stream has already been reached system_error read system_error interrupted The error indicated was reported by the operating system when reading the input stream Stream Example Reading a complete input line user get_until n Line End lt ENTER gt This is one Line lt ENTER gt Line This is one Line End n lt ENTER gt yes Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also get_char 1 2 Reference Manual 282 IF Prolog V5 3 getchar 3 Predicate String processing Access a character in an atom
249. aa a 634 back_parent 0 Branch back to CALL port of parent goal 635 back_subgoal 0 Branch back to CALL port of subgoal 636 break 0 Start new input loop s aso ee hoch ss 4 Gok eh PRS EO ee 637 ally i Exec ltea Prolog goal s ct wee es ea ee BS a we EA 638 continue 0 Continue to next breakpoint 02 4 639 deactivate_stop 0 1 Deactivate breakpoint temporarily 640 error 2 Raise an exception see ewe ee ed 642 exit 0 Force current subgoal to succeed 22 000 fail O Force the current subgoal to fail 0 fast_skip 0 1 Accelerate execution to exit of a subsequent subgoal halt 0 Terminate debugger and IF Prolog help O Display help information 20 nonstop 0 Continue without stopping port 2 Set debugger port lt e ec oe coe bh wR eR eR EERE EEE Rw remove_stop 0 1 Remove explicit breakpoints set_debug_depth i Set structure depth 4 eet hietery 1 Configure history o c ostes ek Oe eae ae RED Owe SDs set_trace_depth 1 Set structure depth for trace outputs set_trace_length 1 Set length of trace field skip 0 1 Execute up to exit of a subsequent subgoal snapshot 0 1 2 Store feld e ea e e epa oe Be eee ee RR step 0 Execute up to next monitored port aooo a stop 4 stop_interac
250. able but a variable was specified type_error atom The argument Alias must be an atom but is a term of another type Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also assign alias 2 current_alias 2 Reference Manual 130 IF Prolog V5 3 catch 3 Predicate Contexts Exceptions Intercept a context jump catch Goal CatchMask SubstituteGoal Module The predicate catch 3 opens a context for intercepting context jumps and calls the goal Goal If Goal succeeds catch 3 is successfully exited By backtracking Goal can return several results If Goal does not or does no longer succeed catch 3 also fails i e backtracking is initiated If throw Term is called while Goal is being executed execution is terminated and Catch Mask is unified with a copy of Term If the unification is successful SubstituteGoal is called If the unification fails the next outer context is used see throw 1 Exceptions which are detected by IF Prolog and which are not processed using a handler see context 2 throw error Error Info is implicitly called where Error indicates the error type and Info is a list of terms of the type InfoName Value which provide additional information about the error InfoName is an atom indicating the type of additional information and Value is any term see also exce
251. able form Output a term in readable form Clear to end of line Clear to end of line Clear to end of screen Clear to end of screen Clear screen Clear screen Determine the cursor position Determine the cursor position Position the cursor Position the cursor Query the screen size Query the screen size Define the body of a module Define a character conversion IF Prolog V5 3 27 Reference Manual Overview by functionality Predicates discontiguous PredicateList dynamic PredicateList end_module end_module Module ensure_loaded Filename export PredicateList import Module Module PredicateList include Filename init Goal initialization Goal meta PredicateList module Module multifile PredicateList import nonotify op Priority Assoc Names private PredicateList reexport Module reexport Module PredicateList set_prolog_flag Flag Value Modules Module Predicate Predicate Module begin_module Module calling_context Module compile Filename current_default_module Module current_module Module end_module end_module Module export PredicateList import Module import Module PredicateList load Filename meta PredicateList Declare discontiguous predicate definition Declare predicates as modifiable Conclude the
252. ack variables are displayed with internal numbers Arguments VariableName Variable Exceptions type_error variable The argument VariableName must be a variable but is a term of another type existence_error variable The argument VariableName specifies a variable that does not occur in the specified clause of the predicate existence_error constraint_variable The argument VariableName is not a constraint variable Reference Manual 680 IF Prolog V5 3 view_variable 0 1 Debugger command Command interface domain_error arity The command view_variable 0 1 was called with an incorrect number of param eters Hints The information described here is formatted in accordance with the interface The appearance of the output therefore depends on the interface See also view_constraints 0 IF Prolog V5 3 681 Reference Manual Command interface Debugger command view_variable 0 1 Reference Manual 682 IF Prolog V5 3 Chapter 7 Overview by functionality of C interface This section contains an overview of the built in functions of the active and passive C interface arranged into groups according to their functionality The name of each C function is printed in bold type Each argument is preceded by its data type The result type of the function stands before the function name Active Prolog goals C Function void PrologClose t_cursor ActGoal BOOLEAN PrologError t_cursor ActGoal TERM Term BOOLEA
253. ad the Prolog flag search_path will be used as search path for files to be read see set_prolog_flag 2 The same applies for open 3 4 The predicate file_test 2 is based on the C function access 2 see 10 IF Prolog V5 3 245 Reference Manual Operating system Predicate file_test 2 Example The current directory contains a file called example pro which belongs to the user user file_test example pro read lt ENTER gt yes Users are normally not allowed to create files in the root directory of the file system user file_test write lt ENTER gt no Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also open 3 4 set_prolog flag 2 Reference Manual 246 IF Prolog V5 3 filepos 2 3 Predicate Stream processing Determine position within an input stream filepos Stream Line filepos Stream Line Column The predicate filepos 2 determines the current line position of the specified input stream Stream and unifies the result with Line The current line position is the number of lines processed plus one The predicate filepos 3 additionally determines the character position of the input line and unifies the result with Column The current character position is the number of characters processed in this line plus one Arguments Stream Stream
254. ad_system 1 IF Prolog V5 3 329 Reference Manual Database Predicate load_system 1 Restore the old system status load_system Filename The predicate load_system 1 loads a system state saved with save_system 1 from File name If Filename does not contain the extension pst and if a file of this name cannot be opened for reading the extension is appended and the resultant filename is used The current database is completely overwritten in the process After load_system 1 the goal user program is activated if the predicate program 0 is defined in the module user Otherwise the input loop of IF Prolog break 0 is started Arguments Filename Atom name of a file Exceptions instantiation_error The argument Filename must not be a variable but a variable was specified type_error atom The argument Filename must be an atom but is a term of another type domain_error file_name The value of the argument Filename is not a valid name for a file permission_error open source_sink The argument Filename specifies a file or a different I O medium that cannot be opened system_error read system_error interrupted The error indicated was reported by the operating system when reading the input stream Filename domain_error save_state The argument Filename specifies a file that does not contain a system state gen erated with save_system 1 or save_runtime 1 Example A system state with a user
255. ail in the section 9 4 on Arithmetic expressions and functions in this manual In particular this section explains when and how the value of an arithmetic expression is formed IF Prolog offers two types of function e Arithmetic functions These take the values of the arguments and evaluate the result according to mathe matical conventions e Logical functions These are defined only for integer arguments These arguments are interpreted as bit sequences The result is always an integer The following tables provide an overview of the arithmetic and logical functions which are available in IF Prolog and which may occur in arithmetic expressions I stands for an integer Q for a rational number R for a floating point number QI for an integer or rational number and N for any possible number For functions with names declared as operators the type of the operator associativity is specified in the Type column and the precedence of the operator is specified in the Prec column see op 3 IF Prolog V5 3 309 Reference Manual Arithmetic Predicate is 2 Arithmetic functions with arity 0 Name Function cputime Used CPU time in seconds time System time in seconds random Random number pi Constant 7 dsize Total size of the database bytes dused Portion of the database used in csize Total size of the local control stack bytes cused Portion of the local control stack used in esize Total size of the extended term
256. ains an actual goal but will only be accessible after the execution of the new current goal has been terminated see PrologClose Therefore nested execution of queries is possible Arguments Module Structure see PrologModule Goal Term VarList Term list of variables in Goal See also PrologModule PrologClose PrologError PrologFetch QueryOpen ParseProlog IF Prolog V5 3 729 Reference Manual Active C interface C Function PrologUndo Undo unification include cpred h void PrologUndo void The function PrologUndo cancels undoes all term manipulations see TermUnify Q TermMake in the current call of a C function All terms constructed since the start of a C function are now void and all term unifications are undone The function PrologUndo is necessary when after a failing unification a C function is not immediately terminated with return FALSE or FAIL Hints A detailed description of macros used in the example to get a more clear implementation of complex C predicates COROUTINE etc can be found in the IF Prolog User s Guide 2 Example The second argument L of the predicate element_of E L shall be a list of Prolog terms By backtracking the first argument E is unified with each term of the list L include cpred h typedef struct size_t no index static BOOLEAN proper_list TERM list TERMCONTEXT context TermContext w
257. al Input output for terms Predicate write_canonical 1 2 Hints The call write_canonical Term is identical to write_term Term quoted true ignore_ops true numbervars false The output produced by write_canonical 1 2 is suitable for re input with read_ term 2 3 Example user write_canonical a 4 7 nl lt ENTER gt a 4 7 yes user write_canonical a b 3 7 17 nl lt ENTER gt 1 Cab a T a 17 0 yes Standard These predicates comply with the definition of the ISO standard for Prolog See also print 1 2 write 1 2 writeq 1 2 write term 2 3 Reference Manual 606 IF Prolog V5 3 write_formatted 2 3 Predicate Formatted input output for terms Formatted output of terms write_formatted Format TermList write_formatted Stream Format TermList The predicate write_formatted 2 outputs the terms specified in TermList to the current output stream in accordance with the formatting instructions in Format while taking the existing operator definitions in the calling module or in the specified Module into account The predicate write_formatted 3 acts in the same way as write_formatted 2 but writes to the specified output stream Stream The specification of Format is analogous to the C function printf 3C see 10 with some Prolog specific enhancements The argument Format can be a string of any characters and formatting sequences where t
258. al Serial lt ENTER gt Serial kb 511000000 lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1A The predicate prolog_serial 1 is new See also system_hostid 1 system_name 1 prolog_version 1 proroot 1 Reference Manual 424 IF Prolog V5 3 prolog_version 1 Predicate System information Query IF Prolog version prolog_version Version The predicate prolog_version 1 unifies Version with an atom which contains the version number of IF Prolog The version number changes with each new release of IF Prolog and can be used to control version specific actions in an application Arguments Version Atom Exceptions type_error atom The argument Version must be a variable or an atom but is a term of another type Example user prolog_version Ver lt ENTER gt Ver 5 1A lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also prolog_serial 1 proroot 1 system_hostid 1 system_name 1 IF Prolog V5 3 425 Reference Manual System information Predicate proroot 1 Query path of IF Prolog system proroot Path The predicate proroot 1 unifies Path with an atom containing the installati
259. al 2 has several solutions for the current call IF Prolog V5 3 197 Reference Manual Contexts Exceptions Predicate current_signal 2 Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also signal_handler 3 signal_control 2 context 2 Reference Manual 198 IF Prolog V5 3 current _socket 3 Predicate Net communication Query communication sockets current_socket Domain Type Socket The predicate current_socket 3 queries endpoints for communication The argument Domain is unified with the communications domain within which communi cation takes place The argument Type is unified with the semantics of the communication The argument Socket is unified by backtracking with a system generated term Arguments Domain Atom internet unix Type Atom datagram stream Socket Socket system defined term Exceptions type_error atom The argument Domain or Type must be a variable or an atom but is a term of another type type_error socket The argument Socket must be a variable or a socket supplied by socket 3 but is a term of another type Hints The sequence of solutions is undefined if current_socket 3 has several solutions for the current call Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode
260. alling module or in the specified Module unless the 2 qualification is used for such a predicate to indicate explicitly the module in which this predicate is visible The predicates activated in the goal are normally executed in the context of the module in which they are defined This does not apply to metapredicates which are executed in the context of calling module or the specified Module unless the 2 qualification is used for a metapredicate to indicate explicitly the module context in which this predicate is to be executed Example The database contains the following clauses user listing lt ENTER gt user is_father_of 2 is_father_of Zeus Athena is_father_of Zeus Apollo is_father_of Cronos Zeus is_father_of Cronos Poseidon yes You can now find all fathers with user findall V is_father_of V _ L lt ENTER gt V _68 L Zeus Zeus Cronos Cronos lt ENTER gt yes And you can find the children with user findall K is_father_of _ K L lt ENTER gt K _68 L Athena Apollo Zeus Poseidon lt ENTER gt yes In the following examples the first argument does not occur in Goal Reference Manual 250 IF Prolog V5 3 findall 3 Predicate Execution control user findall X member Y a b c L lt ENTER gt X _68 Y _69 L _152 _145 _138 lt ENTER gt
261. alphabetical order Predicates which are adjacent to each other in the alphabet and which are similar in function are described together The language constructs directives and the special user defined predicates used by IF Prolog can also be found here Predicates which permit backtracking are indicated by a hash character in front of the functor This character does not appear with predicates not having this capability For metapredicates the argument list is followed by the text Module The module qualification can be specified by 2 Metapredicates are supplied with information on the calling module Directives are special syntactic structures which can be specified in IF Prolog texts and which are processed when these texts are read in e g with consult 1 They are indicated by in front of the functor as they would be written in a Prolog text User definable predicates are automatically called at particular points by IF Prolog if the user has defined them They are identified by the text Body after the argument list The call mode specifies the instantiation of an argument at the time of the call In front of each argument there is a sign or to indicate the call type of the argument as follows The argument is a pure input parameter The current parameter specified in the call must be of the prescribed type and any uninstantiated variables contained in this parame
262. als conjunction 42 disjunction 53 IF THEN conjunction 47 IF THEN ELSE conjunction 296 grammar rules call 401 consult 163 expand 240 operator 44 reconsult 446 transform 240 gsize 309 gused 309 head of a list 812 hexadecimal number IF Prolog V5 3 839 Reference Manual Index syntax 802 history configure 654 import predicates 299 infix operator 813 input byte 266 395 character 268 271 397 399 character string 281 query end of line 93 query end of stream 95 skip line 507 syntax errors 548 term 437 442 input loop generate 123 installation path of IF Prolog system 426 instantiation test 289 367 integer generate 770 syntax 801 test 308 756 unify 787 integer division 309 integer expression test 757 integers generate a sequence 258 interface of a module 354 invocation parameters query 422 iteration for 258 repeat 456 left shift 309 letter test 316 lexical elements 795 line skip 507 list append 77 convert to structure 60 decompose 77 element 812 form from head and tail 161 generate 771 777 head 812 individual element 324 last element 317 number of elements 319 remove sublist 454 reverse 463 sort 527 syntax 811 tail 812 test 758 test membership 344 347 364 unify 788 literal 821 local control stack size 309 used 309 log 309 logical function 309 820 loop for 258 repeat 456 lowercase letters conv
263. am The argument Stream is not a stream which has been opened for input open mode read permission_error input binary_stream The current input stream or the argument Stream must be a text stream but is associated with a binary stream permission_error past_end_of_stream The open option eof_action error was set for the input stream Stream and the end of the stream has already been reached system_error read system_error interrupted The error indicated was reported by the operating system when reading the input stream Stream instantiation_error The argument Options or a subterm must not be a variable but a variable was specified type_error list The argument Options must be a list but is a term of another type domain_error read_option An element of Options specifies an option that is not permitted IF Prolog V5 3 443 Reference Manual Input output for terms Predicate read_term 2 3 syntax_error Syntax errors were detected during analysis of input All the syntax errors de scribed for syntax_error 2 can occur Hints If the read process is interrupted by a signal the predicate fails even if the signal is handled Example user read_term T varnames V lt ENTER gt a X Y lt ENTER gt T a _131 _132 V X _131 Y _132 lt ENTER gt yes user read_term T varnames V singletons S lt ENTER gt a X Y write Y lt ENTER gt T a _150 _151 write _15
264. am is not a stream which has been opened for input open mode read permission_error input binary_stream The current input stream or the argument Stream must be a text stream but is associated with a binary stream permission_error past_end_of_stream The open option eof_action error was set for the input stream Stream and the end of the stream has already been reached system_error read Reference Manual 268 IF Prolog V5 3 get_char 1 2 Predicate Elementary input output system_error interrupted The error indicated was reported by the operating system when reading the input stream Stream type_error atom The argument Character must be a variable or an atom but is a term of another type representation_error in_character The argument Character must be a variable a character or the special atom end_ of_file but is not representable as a single character representation_error character The entity read from the stream is not representable as a single character Example The following predicate is defined for entering words user listing lt ENTER gt h user get_atom 1 get_atom A get_char C get_list C L atom_chars A L user get_list 2 get_list get_list n get_list end_of_file get_list C CIL get_char C1 get_list C1 L yes Applying this repeatedly to an input line would yield user repeat get_atom A lt ENTER gt I
265. am which has been opened for input open mode read Standard This predicate complies with the definition of the ISO standard for Prolog See also set_error 1 set_output 1 current_input 1 current_output 1 current_error 1 IF Prolog V5 3 483 Reference Manual Memory management Predicate set_memory_management 3 Set memory management parameters set_memory_management Area Parameter Value The predicate set_memory_management 3 sets the value of the parameter Parameter relat ing to memory management for the memory area Area IF Prolog manages the memory areas database global constraints local trail and extension Each possesses the parameters minimal_size maximal_size minimal_gap maximal_gap default_gap and trace The values of all but the last parameter are positive integers The parameter trace has the value on or of f The parameters have the following meaning minimal_size Minimum size of the memory area in bytes maximal_size Maximum size of the memory area in bytes 0 if unlimited default_gap The value specified is interpreted as a percentage and is automatically limited to the range 0 1000 After garbage collection the amount of free memory in the area must be at least default_gap percent of the memory used otherwise the size of the memory area is automatically increased The size of the free memory is further restricted by the parameters minimal_gap and maximal_gap If maximal_gap
266. ame Functor the arity Arity and the arguments Args and returns it as the result If an element of the vector is NULL a new Prolog variable is generated for this argument and it is used as the structure argument Arguments Functor Character string name of the structure Arity Integer 0 lt Arity lt 127 Args Vector with Arity term variables Exceptions The following errors cause IF Prolog to be exited implementation_error Arity arity out of range The argument Arity is not within the range 0 127 implementation_error TermMakeUniversal out of memory The function TermMakeUniversal could not be executed successfully due to a lack of memory Example The following simple C function realizes a predicate make_assignment 3 which makes a term of the form Term1 Term2 of its arguments include cpred h BOOLEAN make_assignment_3 void xx make_assignment Term1 Term2 Assignment TERM terms 2 Reference Manual 774 IF Prolog V5 3 Term MakeUniversal C Function Active C interface terms 0 PrologArg 1 terms 1 PrologArg 2 return TermUnify PrologArg 3 TermMakeUniversal 2 terms void Cboot void CPRIM make_assignment 3 make_assignment_3 See also TermMakeCompound TermMakeFunctor TermIsUniversal IF Prolog V5 3 775 Reference Manual Active C interface C Function Term MakeVar Generate a Prolog variable include cpred h
267. amp TermIsInteger PrologArg 2 amp value Reference Manual 768 IF Prolog V5 3 Term MakeFunctor C Function Active C interface amp amp TermUnify PrologArg 3 TermMakeFunctor string value void Cboot void CPRIM make_struct 3 make_struct_3 See also TermMakeCompound TermMakeUniversal TermIsFunctor IF Prolog V5 3 769 Reference Manual Active C interface C Function Term Makelnteger Generate a Prolog integer include cpred h TERM TermMakelInteger long Value The function TermMakeInteger generates a Prolog integer and returns it as the result Arguments Value Integer Exceptions The following error causes IF Prolog to be exited implementation_error TermMakelInteger out of memory The function TermMakeInteger could not be executed successfully due to a lack of memory See also TermlsInteger Reference Manual 770 IF Prolog V5 3 Term MakeList C Function Active C interface Generate a Prolog list include cpred h TERM TermMakeList TERM Head TERM Tail The function TermMakeList generates a Prolog list where Head is used as the list head and Tail as the list tail The generated list is returned as the result If Head or Tail is NULL a Prolog variable is generated instead and is used as the list argu ment Arguments Head Term variable Tail Term variable Exceptions The following error cau
268. and activate_stop activate_stop Numbers deactivate_stop deactivate_stop Numbers remove_stop remove_stop Numbers stop Breakpoint Ports Conditions Actions stop Monitored Variable BindingType Conditions Actions stop_interactive Breakpoint stop_interactive Breakpoint Ports Short as ds ds rs st st Functionality Reactivate current breakpoints Reactivate breakpoints Deactivate all breakpoints temporarily Deactivate breakpoint temporarily Remove all current explicit breakpoints Remove explicit breakpoints Set breakpoint Set breakpoint to the monitoring of variables Set interactive breakpoint Set interactive breakpoint 623 Overview by functionality Debugger commands stop_interactive Breakpoint Ports Conditions Actions stop_ interactive MonitoredVariable BindingType Conditions Actions activate_stop activate_stop Numbers deactivate_stop deactivate_stop Numbers remove_stop remove_stop Numbers stop Breakpoint Ports Conditions Actions stop MonitoredVariable BindingType Conditions Actions stop_interactive Breakpoint stop_interactive Breakpoint Ports stop_interactive Breakpoint Ports Conditions Actions stop_ interactive MonitoredVariable BindingType Conditions Actions Control commands Command abort break call Goal Module halt system abort break call Goal Module
269. andard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also socket 3 current_socket 3 select 3 host_addr 2 net_service 3 socket_accept 3 socket_bind 2 socket_connect 2 socket_close 1 socket_listen 1 2 socket_raw_receive 4 5 socket_send 2 3 socket_shutdown 1 2 Reference Manual 522 IF Prolog V5 3 socket_send 2 3 Predicate Net communication Send data to socket socket_send Socket List socket_send Socket Addr List The predicates socket_send 2 3 transmit data to a socket The predicate socket_send 2 sends data to a connected socket see socket_connect 2 and socket_accept 3 The predicate socket_send 3 sends a datagram to the specified address The argument Socket must be a term representing a socket The argument Addr of socket_send 3 is the address where the data is to be sent The address for internet domain socket must have the form Host Port where Host is either the atom representing the hostname or a single quoted atom or a list of three integers both representing the IP Address of the receiving machine and Port is the port number The address for unix domain socket must be an atom Filename The argument List must be a completely instantiated list of character codes Arguments Socket Socket system defined term Addr Structure Host Port or atom Filename Hos
270. ans of 2 or 2 with an atom that does not name an existing module type_error list The argument List must be a variable or a list but is a term of another type Example The following grammar rules have been entered into the database sentence gt nom_phrase verb_phrase nom_phrase gt dogs verb_phrase gt bark The first grammar rule can be called as follows IF Prolog V5 3 401 Reference Manual Database Predicate phrase 2 user phrase sentence L L dogs bark lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also gt 2 expand_term 2 Reference Manual 402 IF Prolog V5 3 pop_global 2 Predicate Global variables Query global variable and remove value pop_global Name Value Module The predicate pop_global 2 unifies Value with the topmost element of the value stack of the global variable Name in the calling module or in the specified Module and removes this value from the stack If the value stack of the global variable Name is emptied as a result the global variable is deleted unset_global 1 Arguments Name Atom name of a global variable Value Term Exceptions instantiation_error The argument Name must not be a variable but a variable was specified type_error atom The argument Name must be an atom but
271. anual String processing Predicate concat_atom 2 3 user concat_atom a b c _ B lt ENTER gt B a_b_c lt ENTER gt yes user concat_atom a b 15 X lt ENTER gt X ab15 lt ENTER gt yes user concat_atom a Y lt ENTER gt Y ax lt ENTER gt yes user concat_atom Z lt ENTER gt Z lt ENTER gt yes user concat_atom p a n g pang lt ENTER gt yes Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also append 3 atom_concat 3 write_atom 2 match_atom 2 atom split 3 Reference Manual 160 IF Prolog V5 3 connect 3 Predicate List processing Connect a head and a tail to form a list connect List Head Tail The predicate connect 3 unifies the head of List with Head and the rest with Tail Arguments List List Head Term Tail Term Hints The call connect List Head Tail is identical to List Head Tail Exceptions type_error list The argument List must be a variable or a list but is a term of another type Example user connect L alpha beta lt ENTER gt E alpha beta lt ENTER gt yes user connect a b c Head Tail lt ENTER gt Head a Tail b c lt ENTER gt no The last element of List need not necessarily be the empty list IF Prolog V5 3 16
272. applies to the FAILBODY port The maximum structure depth is restricted by this parameter when terms are output by the debugger If 0 is specified there is no restriction The number of goal and clause boxes to be stored for the alpha and Motif interfaces Tracing in activated Tracing is deactivated Reference Manual 208 IF Prolog V5 3 debug_config 3 Predicate Debugger display automatic The user interface is set automatically by the sys tem in accordance with the system environment This value is the default setting unless the system parameter stream was specified when the Prolog system was started see system_parameters 1 alpha The most basic interface for alphanumeric screens is set The I O device must be a terminal and the device driver must be able to perform terminal control functions If this is not the case the value is automatically reset to stream stream The most basic command oriented interface is set It does not require any terminal functions i e it can also be used for redirected input output This value is the default setting if the system parameter stream was specified when the Prolog system was started see system_parameters 1 motif An attempt is made to start the debugger s Motif interface on the default X display see Motif doc umentation If this attempt is unsuccessful the value is automatically reset to alpha motif Display Display is regarded as the specification of an X dis p
273. apply to terms of different types Variable lt Floating point Floating point lt Rational number Rational number lt Integer Integer lt Atom Atom lt Structure The following applies to terms of the same type Variable The order is undefined and the result is therefore random Floating point Arithmetic order Rational number Arithmetic order Integer Arithmetic order Atom Character code order Structure Ordered primarily according to their arity then by the name of the functor and finally by the arguments from left to right Arguments Op Atom lt gt Term1 Term Term2 Term Reference Manual 152 IF Prolog V5 3 compare 3 Predicate Term comparison Exceptions type_error atom The argument Op must be a variable or an atom but is a term of another type Example user compare Op adam zeppelin lt ENTER gt Op lt lt ENTER gt yes user compare lt 3 77 1 lt ENTER gt yes user compare gt 13 hello lt ENTER gt no user compare Op g z g x y lt ENTER gt Op lt lt ENTER gt yes user X is 4 5 Y is 2 10 compare Op X Y lt ENTER gt X 20 Y 20 Op lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Compatibility V5 0B The predicate compare 3 is new IF Prolog V5 3 153 Reference Manual Term comparison Predic
274. arations They can be modified to a certain extent explicitly by the user These include the following e List mode see list_mode 3 e Debug mode see debug_mode 3 e Exception mode see predicate_mode 3 e Modification mode see modify_mode 3 These attributes are retained even if the predicate is deleted with abolish 1 for ex ample Standard This predicate complies with the definition of the ISO standard for Prolog See also retract 1 2 dynamic 1 debug_ mode 3 list mode 3 modify_mode 3 predicate_mode 3 Reference Manual 74 IF Prolog V5 3 abort 0 Predicate Execution control Return to the toplevel loop of IF Prolog abort The predicate abort O is a special predicate that neither succeeds nor fails Its effect is purely procedural and causes normal execution to be interrupted Calling abort 0 returns to the toplevel active input loop of the IF Prolog system break 0 regardless of how many such nested input loops are active The abort message is output to the current error output stream If abort 0 is called in the toplevel input loop IF Prolog remains in this loop If there is no input loop active IF Prolog is exited with an error message Hints The predicate abort 0 is based on throw 1 This predicate is not part of the IF Prolog runtime system and is therefore not available for applications intended for third parties Example user break lt ENTER gt user 2 break lt
275. are destroyed This has the following effects e While executing G Prolog is now committed to the clause where the cut was called as a subgoal e All instantiations made till now when executing G become permanent If the cut is again reached from the right in the course of backtracking the execution of the calling goal G will fail because it is impossible to make any new variable instantiations or to select new clauses A further interpretation of the cut is that a goal can be executed precisely once and in precisely one way if the cut is called at a suitable position normally at the start of the body of a clause Backtracking is not performed The cut has an important function in loops which are constructed using the predicate repeat 0 When used there it prevents a loop from being reentered during backtracking once the termination condition has been encountered Hints 1 0 greatly reduces the readability of programs The cut should therefore be used very sparingly The use of language construct gt 2 can avoid many traditional applications of 0 The language construct 0 is not a predicate so it cannot be redefined The predicates current_predicate 1 and current_visible 2 do not indicate language constructs Explicit module qualification with 2 or 2 is not permitted for language constructs with the exception of call 1 Example In contrast to append 3 the predicate append_x 3 defined here searches only for the f
276. are not inserted into the database If there are already clauses in the database for a predicate defined in Filename they are not deleted before the new clauses are inserted in the database However this applies only if these clauses are not part of an explicitly defined module body in Filename since the definition of a module body see begin_module 1 will first delete any existing body of the same module If the Prolog flag debug is set to on assertz_with_names 2 is used for insertion in the database so that for example listing 0 1 can be used to display the clauses of these predicates with their original variable names Otherwise assertz 1 is used If grammar rules formulated with gt 2 occur in Filename they are interpreted by con sult 1 and converted into normal Prolog clauses Directives occurring in Filename are evaluated and executed according to their functionality This may affect the further operation of consult 1 operator and module definitions for example The following directives are available Directive Description op 3 Define and delete operators char_conversion 2 Define a character conversion include 1 Include a Prolog file in the source text ensure_loaded 1 Insert a Prolog file in the source text once discontiguous 1 Declare discontiguous predicate definition multifile 1 Declare predicates as being scattered over several files init 1 Initialization goal initialization 1 Initialization goal dynamic 1 Declare
277. argument Term must not be a variable but a variable was specified type_error integer The argument Term must be an integer but is a term of another type domain_error single_precision_integer The argument Term must be an integer with machine precision but a big number was specified See also TermlsIntegerExpression TermIsFloat TermMakeInteger Reference Manual 756 IF Prolog V5 3 TermlIsIntegerExpression C Function Active C interface Test for integer expression include cpred h BOOLEAN TermIsIntegerExpression TERM Term long Value The function TermIsIntegerExpression tests whether the term Term is an expression whose result is an integer within the range of values for a C variable of the type signed long If it is the function stores the value of the number in Value and returns TRUE Otherwise it sets the error context and returns FALSE In this case Value is not changed Arguments Term Term variable Value Pointer to an integer number Exceptions instantiation_error The argument Term or a subterm must not be a variable but a variable was specified type_error integer The argument Term must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer See also TermIsInteger TermIsFloatExpression TermMakeInteger IF Prolog V5 3 757 Reference Manual Active C interface
278. arguments These attributes determine the normal structure to which an expression in operator notation corresponds Operator type In Prolog there are three types of operator e prefix operators the operator is located in front of the argument e infix operators the operator is located between two arguments IF Prolog V5 3 813 Reference Manual Prolog Syntax Operators e postfix operators the operator is located after the argument If the arguments of an operator are themselves not expressions in operator notation the type declaration is sufficient to determine its associated normal structure Expression Associated normal structure operator argument operator argument argument operator argument2 operator argument1 argument2 argument operator operator argument If an expression contains more than one operator the type specification is not sufficient alone to uniquely determine which operator is the functor of the associated normal structure and how the arguments are assigned to the different operators This assignment can be made unambiguous by means of parentheses To make the assignment unique even without parentheses each operator is given the at tributes operator precedence and associativity of arguments These two attributes define parentheses implicitly Operator precedence The precedence of an operator is represented by an integer between 1 and 1200 It is defined in the operator declaration
279. at is not an atom existence_error module The argument Goal or Handler or a subgoal is qualified by means of 2 or 2 with an atom that does not name an existing module Hints Exception handling of this nature is only permitted for signals for which active signal handling has been activated see signal_control 2 Before the Handler is activated signal handling for the incoming signal is set to off passive handling In other words signal handling must be reactivated from within the Handler if required The predicate signal_handler 3 is mapped to context 2 The predicate signal_handler 3 is a metapredicate and calls its goal in the calling module or in the specified Module The predicates activated in the goal must be visible in the calling module or in the specified Module unless the 2 qualification is used for such a predicate to indicate explicitly the module in which this predicate is visible The predicates activated in the goal are normally executed in the context of the module in which they are defined This does not apply to metapredicates which are executed in the context of calling module or the specified Module unless the 2 qualification is used for a metapredicate to indicate explicitly the module context in which this predicate is to be executed Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also
280. ate compare 3 See also lt 2 lt 2 gt 2 gt 2 2 Q 2 Reference Manual 154 IF Prolog V5 3 compile 1 Predicate Database Compile a Prolog text compile Filename The predicate compile 1 compiles the Prolog text in the file with the name Filename If Filename does not contain the extension pro and if a file of this name cannot be opened for reading the extension is appended and the resultant filename is used The compiled Prolog text is stored in internal format in a file with the extension cmp This file is then implicitly loaded with the predicate load 1 If Filename contains only module bodies the interface of this module must be known to IF Prolog for compilation and the complete module is stored in the file created In contrast to incremental compilation used with asserta 1 2 etc additional optimizations can be made with compile 1 All the predicates defined in Filename which have not been declared with the dynamic 1 directive can then no longer be modified displayed or tested This applies irrespective of the value of the Prolog flag debug Arguments Filename Atom name of a file Exceptions instantiation_error The argument Filename must not be a variable but a variable was specified type_error atom The argument Filename must be an atom but is a term of another type domain_error file_name The value of the argument Filename is not a valid name for a file
281. ator define 379 383 delete 379 383 infix 813 postfix 814 precedence 814 prefix 813 query 186 syntax 813 type 813 ordering of terms 65 152 output byte 428 character 430 432 newline 362 position cursor 356 389 563 readable format 605 term 411 601 607 613 618 user defined 404 parameters invocation 422 system 561 user defined 596 pattern matching 338 341 pipe create 590 position of a character string in an atom 304 postfix operator 814 precedence of an operator 814 predicate IF Prolog V5 3 841 Reference Manual Index declare 413 export 241 IF THEN ELSE conjunction 296 import 299 reexport 450 prefix atom 111 prefix operator 813 process create 584 fork 584 query ID 587 send signals 588 spawn 584 wait for termination of child 592 production operator 44 profile goal 415 query statistics 418 reset statistics 417 Prolog compiler call 7 Prolog cross referencer call 17 Prolog definition referencer call 8 Prolog flag query 191 set 488 493 Prolog optimizer call 13 Prolog preprocessor call 14 Prolog system call 9 Prolog tag generator call 16 Prolog text compile 155 load 50 163 328 446 Prolog specific characters 794 meaning of 794 Raise an exception 642 random 309 random number 309 rational division 309 rational number decompose 435 denominator 435 numerator 435 syntax 804 test 434 rdiv 309 read term 4
282. ator notation instead of term notation some structures will have different texts but will be identical in their internal representation Assuming the following operator definitions op 100 fy say die op 200 yf say die the following terms will have an identical internal representation say never die never say die die say never die never say say never die die say never die say never die say never IF Prolog V5 3 817 Reference Manual Prolog Syntax Operators The internal representation of a term can best be checked by outputting a term with the predicate write_canonical 1 2 since this predicate ignores operator declarations If a name is defined both as a prefix and as a postfix operator there is no way of decid ing which representation should be selected for outputting the term since output in prefix notation and output in postfix notation are both correct The operator declarations are the same as in the previous example The following call can therefore produce one of the above outputs user write die say never die say never If a left and a right associative operator have the same precedence then ambiguities may arise when a term containing both operators is read Such ambiguities are always resolved in favor of the right associative operator i e in this case the binding of the right associative operator is stronger Such operator declarations should be avoided however 9 3
283. atus save_system Filename The predicate save_system 1 saves all static information concerning the current system status in the file Filename If Filename does not contain the extension pst the extension is appended and the resultant filename Filename pst is used This includes status information on the database e global variables e operators e modules The saved state can be subsequently restored by calling IF Prolog with the parameter r Filename or by using load_system 1 during a Prolog session Arguments Filename Atom Exceptions instantiation_error The argument Filename must not be a variable but a variable was specified type_error atom The argument Filename must be an atom but is a term of another type domain_error file_name The value of the argument Filename is not a valid name for a file permission_error open source_sink The argument Filename specifies a file or a different I O medium that cannot be opened system_error write system_error close system_error flush_output system_error interrupted The indicated error was reported by the operating system when writing on the output stream Filename IF Prolog V5 3 469 Reference Manual Database Predicate save_system 1 Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also save runtime 1 load_system 1
284. auses in the database listing Module listing Functor Module listing Predicate Module The predicate listing O outputs the clauses of all the predicates defined in the calling module or in the specified Module for which the list mode is not off see list_mode 3 as formatted clauses to the current output stream The variables if present in the database are also output with their original names see assertz_with_names 3 If the database does not contain any information on the original names of variables in the listed predicates then symbolic names are assigned for these variables Depending on the argument the predicate Listing 1 restricts output to the predicates with the functor Functor or to the predicate specified by Predicate If the argument is an atom then it may also be a pattern as in match 2 3 and all the predicates matching the pattern are listed Arguments Predicate Structure with the format Functor Arity Functor Atom Arity Integer 0 lt Arity lt 127 Exceptions instantiation_error The argument Predicate Functor or Arity must not be a variable but a variable was specified type_error atom The argument Functor must be an atom but is a term of another type type_error integer The argument Arity must be an integer but is a term of another type domain_error not_less_than_zero The argument Arity must be a positive integer but is negative representatio
285. be a variable but a variable was specified type_error array The argument Array must be an array but is a term of another type type_error integer The argument Index must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer domain_error array_size The argument Index must be a positive integer less than or equal to the number of elements in the array but is not positive or larger Furthermore if an arithmetic expression is specified for the argument Index all the exceptions for is 2 can occur Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1A The predicate get_array 3 is new See also arg 3 array 1 2 create_array 2 set_array 3 IF Prolog V5 3 265 Reference Manual Elementary input output Predicate get_byte 1 2 Input a byte get_byte ByteCode get_byte Stream ByteCode The predicate get_byte 1 reads the next byte from the current input stream current_ input and unifies ByteCode with its integer value The predicate get_byte 2 acts in the same way for the specified input stream Stream If the end of the input stream has been reached ByteCode is unified with 1 The predicates can be applied only for binary streams see open 3 4 Arguments Stream Stream system define
286. be rock tipora OR we eee es 233 exception_handler 3 Define local exception handling 236 exe 1 2 Overlay process lt e cos ettor Boke Eh eR Ree Le ERE 238 expand_term 2 Transform a grammar rule oaoa we A we ees 240 xport Export predicates o c ss coca taric anpi dap tisa 241 fail 0 Initiate Dackiracking e i ee kie dE OS ee eS 243 file_test 2 Check access permission for a file 245 filepos 2 3 Determine position within an input stream 247 findall 3 Find all solutions of a goal co lt s sceo we ee eee ee ees 249 float 1 Test for floating point number aoa 4 ee eee wd 252 float_format 2 Query and set floating point format 253 flush_output 0 1 Flush the buffer of an output stream 256 for 3 Generate a sequence of integers 2 02000 258 functor 3 Generate or analyze a structure 2 024 261 garbage_collection 1 Activate garbage collection 264 get_array 3 Query array element 2 0204 265 Set byee 1 2 Inp t a ee so ses eo eo wh ee he es 266 pet chars 1 2 lat acer s s es sorado tresk ee eee HY SO ee 268 get code 1 2 Input a citer sa nk ea Ew KES God OS Go ea 271 get_file_info 2 3 Get operating system information on files 273 get_global 2 Query the value of a global variable 276 get_last 2 3 Determine the cursor position oo
287. but is a term of another type Hints The first element of ParameterList need not match the name given by the user on the command line it may also be an appropriately expanded pathname under which IF Prolog was found in the system This name will usually vary from system to system Example The file example pro contains the following Prolog program program system_parameters List write List nl Calling IF Prolog as shown below would then return IF Prolog V5 3 561 Reference Manual System information Predicate system_parameters 1 prolog nonotify c example data hello lt ENTER gt IF PROLOG V5 1 Copyright C Siemens Nixdorf Information Systems AG 1996 prolog nonotify c example Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also program _parameters 1 user_parameters 1 Reference Manual 562 IF Prolog V5 3 tab 1 2 Predicate Elementary input output Move the cursor forward tab Number tab Stream Number The predicate tab 1 outputs Number spaces on the current output stream current_ output The predicate tab 2 has the same effect but on the specified output stream Stream If Number is less than 1 or negative the predicates tab 1 2 has no effect Arguments Number Integer or integer expression Stream Stream system defined term or alias a
288. by functionality C interface BOOLEAN Unify term with structure TermUnifyUniversal TERM Term STRING Functor ARITY Arity TERM Args BOOLEAN Unify terms TermUnifyVar TERM Term1 TERM Term Reference Manual 690 IF Prolog V5 3 Chapter 8 Reference section on C functions This section contains descriptions of all functions of the C interface and the device driver interface in alphabetical order A detailed description of all C interfaces and more examples of the use of C interfaces can be found in the IF Prolog User s Guide 2 The function prototype is noted in ANSI ISO C syntax notation 691 Active C interface C Function Cbhoot Link a C function to IF Prolog include cpred h void Cboot void The function Cboot is called automatically when IF Prolog is started It is used to link all the user defined C predicates and device drivers to IF Prolog Hints An empty Cboot function supplied by he system is used if the user did not define an own Cboot function See also Cshutdown CPRED CPRIM MCPRIM MCPRED DeviceCreate Reference Manual 692 IF Prolog V5 3 CPRED C Function Active C interface Add a complex C function to IF Prolog include cpred h void CPRED STRING Functor ARITY Arity CPREDFUN Function size_t Size The function CPRED is used to incorporate the predicate Functor Arity into IF Prolog The predicate is
289. can always be addressed via the built in alias current_input as well IF Prolog V5 3 471 Reference Manual Stream processing Predicate see 1 Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also seen 0 seeing 1 set_input 1 error_tell 1 tell 1 open 3 4 assign_alias 2 Reference Manual 472 IF Prolog V5 3 seeing 1 Predicate Stream processing Query current input stream seeing Stream The predicate seeing 1 unifies Stream with the current input stream The current input stream may be a stream that was set with see 1 or set_input 1 Arguments Stream Stream system defined term or alias atom Exceptions domain_error stream_or_alias The argument Stream must be a variable or an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream Hints The predicate seeing 1 can unify Stream with an alias or the filename that was possibly used with see 1 or open 4 All input predicates that have no explicit stream argument refer to the current input stream This stream can always be addressed via the built in alias current_input as well Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog
290. cate profile_reset 0 is new See also profile 1 2 profile_stat 0 1 trace 1 trace_output 4 trace_config 3 debug 1 call 1 set_prolog flag 2 import 1 IF Prolog V5 3 417 Reference Manual Profiling Predicate profile_stat 0 1 Query profiling statistics profile_stat profile_stat List The predicate profile_stat 1 queries the profiling data The argument List is unified with an unsorted list of compound terms of the form profile_data Predicate Port Count where Predicate is a predicate indicator Port is an atom and Count is a positive integer The predicate profile_stat 0 outputs the profiling statistics sorted by predicate name to the current output stream Arguments List List Predicate Structure with the format Functor Arity Functor Atom Arity Integer 0 lt Arity lt 127 Port Atom call exit fail redo suspend wakeup error failmatch enterbody exitbody redobody trymatch failbody Count Integer Exceptions type_error list The argument List must be a variable or a list but is a term of another type Hints The profiling predicates are included in the module profiler This module must be imported before the predicates can be used These predicates are not part of the IF Prolog runtime system and are therefore not available for applications intended for third parties Standard These predicates are not required by the ISO standard for Prolog Therefore
291. cated in the module user i e all subsequent predicate definitions and directives relate to the module user until a new module is defined or until the load process is terminated Arguments Module Atom name of a module Exceptions Errors in directives are detected with consult 1 reconsult 1 or compile 1 No exceptions are generated Instead only error messages are output on the current error output stream This directive can produce the following error messages instantiation_error The argument Module must not be a variable but a variable was specified type_error atom The argument Module must be an atom but is a term of another type existence_error module The argument Module is not the name of an existing module domain_error current_module The argument Module is not the name of the current module permission_error directive module The specified directive end_module 1 is not valid in this position IF Prolog V5 3 225 Reference Manual Module concept Directive end_module 0 1 Hints The atom end_module is defined as a prefix operator Directives are evaluated during consultation see consult 1 reconsult 1 or compi lation see compile 1 procmp command Standard The directive end_module 0 1 is not required by the ISO standard for Prolog There fore it is not available in ISO compatibility mode see Prolog flag iso See also module 1 begin module 1 import 1 2 export 1 reexport 1 2 meta 1
292. cceeds if the concatenation of the elements in List can be unified with Atom If all elements of List are atoms the predicate acts in the way as concat_atom 2 If any elements of List are variables IF Prolog finds by backtracking such atoms that the concate nation of the elements forms the atom Atom The predicate match_atom 2 can be used for simple pattern matching instead of match 2 Arguments List List of atoms or variables Atom Atom Exceptions type_error list The argument List must be a list but is a term of another type type_error atom An element of List must be an atom but is a term of another type instantiation_error The argument Atom must not be a variable but a variable was specified type_error atom The argument Atom must be an atom but is a term of another type Example user match_atom A B C abc lt ENTER gt A B C abc lt ENTER gt A 2 B a C be lt ENTER gt A a IF Prolog V5 3 341 Reference Manual String processing Predicate match_atom 2 B a ks C bc lt ENTER gt A 5 33 B ab C c lt ENTER gt A a B b C c lt ENTER gt A ab B FD G c lt ENTER gt A eo B abc G gt lt ENTER gt A a B be G gt lt ENTER gt A ab B c G gt lt ENTER gt A abc B 9 C gt lt ENTER gt no user match_atom A B C A 9 B 3 C D lt ENTER gt yes user match_atom p a n
293. ce of operators type_error atom The argument Assoc or an element of Names must be an atom but is a term of another type domain_error operator_specifier The argument Assoc is not a valid type for an operator definition type_error list The argument Names must be a regular list or an atom but is a term or another type or not regular permission_error modify operator The argument Names specifies an existing operator whose definition is incompat ible with the new definition permission_error create operator The argument Names specifies an existing operator that may not be redefined Hints The section 9 3 1 on Converting expressions into equivalent normal structures contains a detailed description of the significance of the precedence and the type of an operator when an expression is converted into an equivalent normal structure A list of built in operators can be found in this manual in the section 9 3 2 Different operators may have the same name they are then distinguished on the basis of their type A prefix operator and an infix operator with the same name are different and may have different priorities For example IF Prolog has two different built in operators with the name the subtraction operator defined as op 500 yfx and the negation operator defined as op 200 fy If expressions with operators of the same precedence are used in the argument area of a non associative operator when entering te
294. cessMode filepos Stream Line filepos Stream Line Column flush_output flush_output Stream open DeviceAndName Mode Stream open DeviceAndName Mode Stream Options reset_streams see Stream seeing Stream seen set_error Stream Query global variable and remove value Set value of a global variable Set value of a global variable Delete a global variable Define an alias for an input output stream Cancel an alias for an input output stream Close an input output stream Close an input output stream Query aliases of input output streams Query information on device drivers Query current error output stream Query current input stream Query current output stream Query information on device drivers Control an input output device Edit a file Edit a file Set current error output stream Query current error output stream Reset current error output stream Check access permission for a file Position within an input stream Position within an input stream Flush the buffer of an output stream Flush the buffer of an output stream Open an input output stream Open an input output stream Restore default values for current streams Set current input stream Query current input stream Reset current input stream Set current error output stream Reference Manual 24 IF Prolog V5 3 Predicates Overview by functionality set_input Stream set_output Stream set_stream_position Stream Pos
295. ck tracking and unification A ground term contains no variables Conclusion lefthand part of a clause implementation part of a module Contains predicate and operator definitions import infix notation Making a predicate from another module visible and thus usable Structure notation where the operator is located between the operands e g A B instantiated variable Variable which is instantiated with a constant or a compound instantiation list literal load local variable logical variable metapredicate term Substitution of a variable by a non variable A Prolog term either the empty list or a compound term whose functor is and which has two arguments the second of which is a list Atom or structure Reading compiled modules into the database Variable which is visible in only one clause A term which can represent any term A metapredicate has an additional argument which specifies the module in whose context it is to be executed Reference Manual 832 IF Prolog V5 3 Appendix C Glossary module module body module interface operator overflow parser postfix notation predicate prefix notation predicate indicator principal functor procedure Prolog flag Prolog text proof proof tree qualification query recursion resolution rule side effect stack statement Logical collection of predicates a module has a mod
296. cking for all matching clauses which were found in the database at the time of the first call even if they have since been modified logic update view Arguments Head Structure atom Body Term VarList List in the form Name Variable Name Atom Variable Variable Exceptions instantiation_error The argument Head must not be a variable but a variable was specified type_error callable The argument Head must have the syntactical structure of a clause head permission_error access static_procedure The argument Head specifies a predicate that was not declared as dynamic type_error callable The argument Body must have the syntactical structure of a Prolog goal type_error list The argument VarList must be a variable or a list but is a term of another type type_error assignment An element of VarList is not an assignment with the format Name Variable type_error atom The argument Name must be a variable or an atom but is a term of another type type_error variable The argument Variable must be a variable but is a term of another type Reference Manual 142 IF Prolog V5 3 clause_with_names 3 Predicate Database Hints The predicate clause_with_names 3 is a metapredicate and considers only predicate definitions which are visible in the calling module or in the specified Module Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibili
297. cktrace Value is the sequence of goals that led to the error The order of the additional information is not defined Info can also be extended to include additional information The identifiers listed above should only be used according to their meaning Arguments Error Structure or atom Info List containing elements of the type InfoName Value InfoName Ground term Value Term Exceptions instantiation_error The argument Error Info or InfoName must not be a variable but a variable was specified Reference Manual 234 IF Prolog V5 3 exception 2 Predicate Contexts Exceptions type_error list The argument Info must be a list but is a term of another type type_error assignment An element of Info is not an assignment with the format InfoName Value Hints Exceptions are implicitly raised by IF Prolog when errors occur Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also context 2 exception_handler 3 throw 1 IF Prolog V5 3 235 Reference Manual Contexts Exceptions Predicate exception_handler 3 Define local exception handling exception_handler Goal Exception Handler Module The predicate exception_handler 3 executes Goal and enables exceptions to be processed If Goal succeeds exception_handler 3 is successfully exited Goal can be re executed by backtracking
298. cpred h BOOLEAN TermIsFloat TERM Term double Value The function TermIsFloat tests whether the term Term is a number that can be repre sented as a floating point number If it is the function stores the value of the number in Value and returns TRUE Otherwise it sets the error context and returns FALSE In this case Value is not changed Arguments Term Term variable Value Pointer to a floating point number Exceptions instantiation_error The argument Term must not be a variable but a variable was specified type_error real The argument Term must be a number whose value can be converted implicitly into a floating point number but is a term of another type evaluation_error overflow The argument Term is a number for which an overflow occurred during its implicit conversion into a floating point number See also TermIsFloatExpression TermIsInteger TermMakeF loat Reference Manual 752 IF Prolog V5 3 TermIsFloatExpression C Function Active C interface Test for floating point expression include cpred h BOOLEAN TermIsFloatExpression TERM Term double Value The function TermIsFloatExpression tests whether the term Term is an expression whose result can be represented as a floating point number If it is the function stores the value of the number in Value and returns TRUE Otherwise it sets the error context and returns FALSE In this case
299. cuted for a system module domain_error arity The command view_module 0 1 was called with an incorrect number of parame ters Hints The information described here is formatted in accordance with the interface The appearance of the output therefore depends on the interface See also view _predicate 0 1 stop 4 stop_interactive 1 2 4 IF Prolog V5 3 675 Reference Manual Command interface Debugger command view_predicate 0 1 Display listing of a predicate view_predicate v view_predicate Predicate v Predicate The view_predicate 0 1 command displays the predicate Predicate from the Prolog data base The predicates are displayed with the clause and subgoal numbers These numbers can be used with stop 4 and stop_interactive 1 2 4 when a breakpoint is created If this command is called without parameters the current predicate is displayed Arguments Predicate Expression with the format e Module Functor Arity e Functor e Module Functor Functor Atom Module Atom name of a module Arity Integer 0 lt Arity lt 127 Exceptions instantiation_error The argument Predicate or a subterm must not be a variable but a variable was specified type_error predicate_indicator The argument Predicate must be a predicate indicator with the above mentioned format but is a term of another type type_error atom The name of the predicate Predicate or the specified Module must be an atom type_error
300. d Example user bagof X current_op V fy X L lt ENTER gt X _68 V 200 L lt ENTER gt X _68 V 900 L not lt ENTER gt no user bagof X X 1 X 2 X 1 S lt ENTER gt X _152 S 1 2 1 lt ENTER gt yes user bagof X Y X 1 Y 1 X 2 Y 2 X 1 Y 3 S lt ENTER gt X _152 S 1 2 1 lt ENTER gt IF Prolog V5 3 119 Reference Manual Execution control Predicate bagof 3 yes Standard This predicate complies with the definition of the ISO standard for Prolog See also call 1 findall 3 setof 3 2 2 set_prolog_flag 2 Reference Manual 120 IF Prolog V5 3 begin_module 1 Directive Module concept Define the body of a module begin_module Module begin_module Module The directive begin_module 1 marks the start of the body of the module Module The body contains a declaration part containing directives e g initialization 1 or import 1 2 and the implementation part of the module i e clauses of the predicates At the time the directive is processed the interface of the module must be known to IF Prolog This applies if the interface of Module was defined in the Prolog text before the directive begin_module 1 or the interface was loaded into IF Prolog before the directive was processed The body of one module ends with the start of a new module module 1 at the start of another body begin_mo
301. d Body clause_with_names Head Body VarList current_predicate Predicate current_visible DefModule Predicate listing listing Functor listing Predicate predicate_type Predicate Type Predicate attributes debug_mode Predicate Before After discontiguous PredicateList dynamic PredicateList export PredicateList import Module import Module PredicateList list_mode Predicate Before After meta PredicateList Q modify_mode Predicate Before After multifile PredicateList Read in a Prolog file Remove a clause from database Remove a clause from database Remove a clause from database Remove a clause from database Save system status for creating applications Save current system status Search the database for specific clauses Search the database for specific clauses Query visible predicates Query visible predicates List the clauses in the database List the clauses in the database List the clauses in the database Query predicate type Query and set the debug mode of a predicate Declare discontiguous predicate definition Declare predicates as modifiable Export predicates Import predicates Import predicates selectively Query and set the list mode of a predicate Declare metapredicates Query and set the modify mode of a predicate Declare predicates as being scattered over several files Reference Manual 30 IF
302. d for such a predicate to indicate explicitly the module in which this predicate is visible The predicates activated in the goal are normally executed in the context of the module in which they are defined This does not apply to metapredicates which are executed IF Prolog V5 3 71 Reference Manual Execution control Language construct 1 in the context of the specified Module unless the 2 qualification is used for a meta predicate to indicate explicitly the module context in which this predicate is to be executed Example The language construct 1 can be used to call a goal without variables being instan tiated user member X a b lt ENTER gt X _68 lt ENTER gt yes Standard This language construct complies with the definition of the ISO standard for Prolog See also not 1 call 1 fail 0 2 2 set_prolog_flag 2 Reference Manual 72 IF Prolog V5 3 abolish 1 Predicate Database Remove a predicate from the database abolish Predicate Module The predicate abolish 1 removes all clauses matching the predicate indicator Predicate from the database based on its visibility in the calling module or in the specified Module Attributes of the predicate defined by the declarations dynamic 1 or meta 1 are unaffected If Predicate does not exist in the calling module or in the specified Module abolish 1 still succeeds Arguments Predicate Structure of
303. d system state in the file Filename will be modified A saved system state can be generated with the predicates compile 1 save_module 1 save_system 1 or save_runtime 1 Optimizing an already optimized system state has no effect The save state generated by the command procmp is already optimized The size of the file can increase by optimization This does not mean that the runtime memory requirement will also increase After a successful optimization the optimizer exits with the exit value 0 If an error occurs a message is printed and the optimizer exits with the exit value 1 Exceptions illegal savestate The file Filename is not a legal save state not enough memory The optimizer does not get enough dynamic memory by the operating system could not open file The file Filename does not exist or cannot be opened for reading and writing could not open temporary file A temporary file could not be opened write error An error occurred during writing of the file This file is now inconsistent and will therefore be removed read error An error occurred during reading a file usage proopt was called without or with more than one parameters See also procmp compile 1 save module 1 save_system 1 IF Prolog V5 3 13 Reference Manual Prolog system System command propp Invoke the Prolog preprocessor propp Flag Filename The command propp preprocesses a Prolog file that may contain conditional
304. d term or alias atom ByteCode Integer 1 lt ByteCode lt 255 Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error input stream The argument Stream is not a stream which has been opened for input open mode read permission_error input text_stream The current input stream or the argument Stream must be a binary stream but is associated with a text stream permission_error past_end_of_stream The open option eof_action error was set for the input stream Stream and the end of the stream has already been reached system_error read L A tapi eer The error indicated was reported by the operating system when reading the input stream Stream Reference Manual 266 IF Prolog V5 3 get_byte 1 2 Predicate Elementary input output type_error integer The argument ByteCode must be a variable or an integer but is a term of another type representation_error in_byte The argument ByteCode must be a variable or an integer in the range 1 lt Byte Code lt 255 Standard These predicates comply with the definition of the
305. d variable It is instantiated to a system generated term Mode specifies the I O direction for which the stream is to be opened The following entries are possible read The stream is opened for reading write The stream is opened for writing If the DeviceAndName object to be opened e g a file already exists the original contents are overwritten append The stream is opened for writing If the DeviceAndName object to be opened e g a file already exists the stream is appended to the original contents of the object without overwriting Options must be specified in the form of a list which may contain the following elements type Type This specification defines the type of stream The following entries are possible for Type text For a stream containing characters default binary For a stream containing binary data The text and binary types are equivalent under UNIX Other operating systems may involve specific conversions when certain characters are read written buf fer Buffering Defines how data is to be buffered by IF Prolog The following entries are pos sible for Buffering no No buffering line Line buffering only meaningful with the text option IF Prolog V5 3 385 Reference Manual Stream processing Predicate open 3 4 full reposition Bool Device dependent buffering default Enables positioning and subsequent repositioning within the stream The follow ing entries are possible for B
306. d with a list of character codes including binary zero If no data have been received yet socket_raw_receive 4 5 will block control until data arrive Provisional inquiry whether data exist is possible by select 4 The argument Length is unified with the integer length of the received data up to the supplied buffer size If the receiving socket is designated as non blocking see set_socket_option 3 and nothing has been received List will be unified with the empty list Length will deliver zero and processing continues Arguments Socket Socket system defined term Size Integer expression Addr Structure Host Port or Atom Filename Host Atom Port Integer Filename Atom List List of character codes Length Integer IF Prolog V5 3 519 Reference Manual Net communication Predicate socket_raw_receive 4 5 Exceptions instantiation_error The argument Socket must not be a variable but a variable was specified type_error socket The argument Socket must be a socket supplied by socket 3 but is a term of another type domain_error socket The argument Socket must be a currently open socket supplied by socket 3 type_error integer The argument Size must be an integer but is a term of another type type_error host port The argument Addr must be a variable or a structure of the form Host Port but is a term of another type type_error atom The argument Host must be a variable or an atom but is a term of another type
307. d with a system error message Arguments Argno Integer 1 lt Argno lt Arity of Term Term Term variable Exceptions The following errors cause IF Prolog to be exited implementation_error Argno argno out of range The argument Argno is not within the prescribed range of values implementation_error TermArg compound term expected The argument TermArg is not a structure See also PrologArg TermDecompose Reference Manual 740 IF Prolog V5 3 TermCloseList C Function Active C interface Close a Prolog list include cpred h BOOLEAN TermCloseList TERM Tail The function TermCloseList closes a list opened by TermOpenList and built by Term AddList Technically this function unifies Tail with an empty list If unification is successful the function returns TRUE otherwise it returns FALSE Arguments Tail Term variable Example See example at TermAddList See also TermAddList TermOpenList TermUnifyNil IF Prolog V5 3 741 Reference Manual Active C interface C Function TermCollect TermCollectSequence Release term variables include cpred h void TermCollect TERMCONTEXT Context void TermCollectSequence TERMCONTEXT Context size_t N TERM TermList These functions release all term variables that were generated since Context was determined with the exception of the pointers to the term variables listed
308. d with an open stream permission_error open source_sink An element of Options is reposition true but it is not possible to reposition this stream Hints With access mode read the Prolog flag search_path will be used as search path for files to be opened see set_prolog_flag 2 Standard This predicate complies with the definition of the ISO standard for Prolog The option buffer is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso IF Prolog V5 3 387 Reference Manual Stream processing Predicate open 3 4 See also close 1 2 stream_device 2 stream_control 2 stream_property 2 Reference Manual 388 IF Prolog V5 3 outtab 1 2 Predicate Elementary input output Position the cursor outtab Position outtab Stream Position The predicate outtab 1 sets the cursor in the current output stream current_output to the specified Position on the current line provided the cursor was previously to the left of Position Otherwise the cursor is moved to the specified Position on the next line The predicate outtab 2 has the same effect but on the specified output stream Stream Arguments Position Integer or integer expression Stream Stream system defined term or alias atom Exceptions instantiation_error The argument Stream or Position must not be a variable but a variable was specified type_err
309. dbuf Size of output buffer integer type Type of the socket atom Arguments Socket Socket system defined term Option Atom Value Integer or atom on off Exceptions instantiation_error The argument Socket must not be a variable but a variable was specified IF Prolog V5 3 279 Reference Manual Net communication Predicate get_socket_option 3 type_error socket The argument Socket must be a socket supplied by socket 3 but is a term of another type domain_error socket The argument Socket must be a currently open socket supplied by socket 3 type_error atom The argument Option must be a variable or an atom but is a term of another type domain_error socket_option The argument Option is not in the prescribed range of values Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also socket 3 current _socket 3 set_socket_option 3 net_service 3 socket_accept 3 socket _bind 2 socket_connect 2 socket_close 1 socket_listen 1 2 socket_receive 2 3 socket_raw_receive 4 5 socket_send 2 3 socket_shutdown 1 2 Reference Manual 280 IF Prolog V5 3 get_until 3 4 Predicate Elementary input output Read up to a specific character get_until SearchChar Text EndChar get_until Stream SearchChar Text EndChar The predicate get_until 3 reads characters from the current input
310. de 3 e Exception mode see predicate_mode 3 e Modification mode see modify_mode 3 These attributes are retained even if the predicate is deleted with abolish 1 for ex ample Reference Manual 322 IF Prolog V5 3 list_mode 3 Predicate Database Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also abolish 1 listing 0 1 dynamic 1 modify_mode 3 IF Prolog V5 3 323 Reference Manual List processing Predicate list_nth 3 Access elements of a list list_nth Position List Element The predicate list_nth 3 succeeds if Element is unifiable with the element of List at the position specified by Position The first list element has the Position 1 The following cases are possible 1 Position is an integer The predicate succeeds if the element of List at the position specified by Position is unifiable with Element If Position is 0 zero or greater than the length of List the predicate fails 2 Position is uninstantiated Position is instantiated to the first position where Element is unifiable with an element of List The predicate is not backtrackable even if Element occurs multiply in List Arguments Position Integer or integer expression List List Element Term Exceptions instantiation_error The argument List must not be a variable but a variable was specified type_
311. ded with the command line option 1 or the predicate load 1 After a successful compilation the compiler exits with the exit value 0 If an error occurs a message is printed and the compiler exits with the exit value 1 In this case no result file is created The command procmp processes some command line options which are also valid for the command prolog c File 1 File These options can be used to provide module interfaces of modules from which predicates are imported sp Path This option determines the search path of files It is used as search path for files to be loaded or included see include 1 nowarnings Suppress the output of possible warning messages iso Only the features required by the ISO standard are available The implementa tion specific extensions of IF Prolog are not available Exceptions All the error messages and warnings from read_term 2 assertz 1 and assertz_ with_names 2 may occur See also prolog proopt compile 1 save system 1 save module 1 IF Prolog V5 3 7 Reference Manual Prolog system System command procref Invoke the Prolog definition referencer procref Flag Filename Filename The command procref generates a list of defined predicates with declaration information from Prolog source files and outputs the list on standard output If the file Filename exists and is readable this is the input file Otherwise if Filename does not already have a pro
312. def A lt ENTER gt A abcdef lt ENTER gt yes user atom_concat A B abc lt ENTER gt A ae B abc lt ENTER gt IF Prolog V5 3 103 Reference Manual String processing Predicate atom_concat 3 no Standard a bce lt ENTER gt ab c lt ENTER gt abc gt lt ENTER gt This predicate complies with the definition of the ISO standard for Prolog See also concat_atom 2 3 atom_part 4 atom_prefix 3 atom suffix 3 getchar 3 index 3 sub_atom 5 atom_split 3 Reference Manual 104 IF Prolog V5 3 atom_length 2 Predicate String processing Count the characters in an atom atom_length Atom Length The predicate atom_length 2 unifies Length with the number of characters in the atom Atom Arguments Atom Atom Length Integer Exceptions instantiation_error The argument Atom must not be a variable but a variable was specified type_error atom The argument Atom must be an atom but is a term of another type type_error integer The argument Length must be a variable or an integer but is a term of another type domain_error not_less_than_zero The argument Length must be a positive integer but is negative Example The atom short is 5 characters long user atom_length short 5 lt ENTER gt yes Single quotes used in the external representation are not part of an atom user atom_length ATOM X lt ENTER gt X 4 lt ENTER gt yes
313. defined database has been saved with save_system 1 Reference Manual 330 IF Prolog V5 3 load_system 1 Predicate Database user listing lt ENTER gt user tst 1 tst 1 tst 2 tst 3 yes user save_system example lt ENTER gt yes This system state and hence this database also can be restored in a later IF Prolog session user load_system example lt ENTER gt user listing lt ENTER gt k user tst 1 tst 1 tst 2 tst 3 yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also save_system 1 load 1 IF Prolog V5 3 331 Reference Manual Operating system Predicate localtime 9 Determine the date and time localtime Time Year Month Day DoW DoY Hour Min Sec The predicate localtime 9 converts a system time see function time in is 2 into date and time information according to the local time zone The individual arguments are unified with the following information as integers Year Year number 4 digits Month Month number 1 12 Day Day of month 1 31 DoW Day of week 1 7 Mon Sun DoY Day in year 1 366 Hour Hours 0 23 Min Minutes 0 59 Sec Seconds 0 59 Arguments Time Integer or integer expression Year Integer 1900 lt Year Month Integer 1 lt Month lt 12 Day Integer 1 l
314. defined predicate portray 2 in the calling module or in the specified Module to output Term if Term is not a variable If the call does not succeed e g because portray 2 is undefined fails or returns an exception the output is the same as with write 1 2 If Term is a structure the attempt to call portray 2 is repeated for each subterm in Term Arguments Stream Stream system defined term or alias atom Term Term Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error output stream The argument Stream is not a stream which has been opened for output open mode write or append system_error write system_error close system_error flush_output system_error interrupted The indicated error was reported by the operating system when writing on the output stream Stream Hints The call print Term IF Prolog V5 3 411 Reference Manual Input output for terms Predicate print 1 2 is equivalent to write_term Term portrayed true numbervars true Example Output of all integers as floating point numbers
315. defined with set_global 2 or push_global 2 at which time they are assigned a value The names of the global variables declared in the module can be queried with current_global 1 The definition of a global variable is canceled with the predicate unset_global 1 Value Any term is valid as the value for a global variable The creation and removal of global variables and the assignment of values to them are side effects of Prolog goal execution and are therefore not affected by backtracking In particular the value assignment can be overwritten as often as you like by calling set_global 2 Temporal validity A global variable is valid from the moment it is defined by means of set_global 2 or push_ global 2 It is retained for the remainder of the Prolog session even after a procedure has been termi nated A global variable loses its validity when the goal unset_global 1 is called or at the end of the Prolog session Logical scope In contrast to Prolog variables global variables can be accessed from all predicates by their names Global variables are set up on a module specific basis and are visible only in this module All the predicates which are used to process global variables are metapredicates so that it is possible to access a global variable in a different module by specifying the appropriate module name user set_global var 5 my_module yes user current_global var no user current_global var my_mod
316. definition of a module Conclude the definition of a module Insert a Prolog file in the source text once Export predicates Import predicates Import predicates selectively Include a Prolog file in the source text Initialization goal Initialization goal Declare metapredicates Define a module Declare predicates as being scattered over several files Do not output load message Define and delete operators Declare predicates as private Reexport predicates Reexport predicates Set value of a Prolog flag Specify the module of the called predicate Specify module context for predicate call Define the body of a module Query the module argument of metapredicates Compile a Prolog text Query current module Query modules Conclude the definition of a module Conclude the definition of a module Export predicates Import predicates Import predicates selectively Load compiled Prolog text Declare metapredicates Reference Manual 28 IF Prolog V5 3 Predicates Overview by functionality module Module Define a module private PredicateList Declare predicates as private reexport Module Reexport predicates reexport Module PredicateList save_module Filename set_default_module Module unload Module Grammar rules Argl gt Arg2 expand_term Termln TermOut phrase Goal List Database manipulation Filename Filename abolish Predicate asserta
317. depth first search directive disjunction dynamic predicate error context exception export expression extended term fact flag functor global variable goal ground head of a module Is defined by the directives which are possible in it Search strategy in proof trees which continues to pursue only one path until that path is successful or ends in a blind alley In the latter case for example backtracking can be initiated Structure having the functor and arity 1 A directive is eval uated when Prolog text is read in ORing of statements A statement A B is true when at least one of the statements A or B is true Predicate whose clauses may be be modified during execution Context in which an error is handled Programmable event In the event of user errors the system branches to the part of the program defined to handle this ex ception If the exception is not caught the system issues an error message Making a predicate visible to and thus usable by other modules A term consisting of numbers and compound terms with evalu able functors Combination of terms using operators Fact concerning the properties and names of objects A fact describes a clause whose body is true see Prolog flag The name of a predicate or structure Variable whose scope is not local to a clause and whose value is not lost during backtracking Term whose proof is attempted with depth first searching ba
318. dicate trace_output 4 is called with Port as a null atom and Goal as the term error Error Info The argument VariableNames contains the empty list Arguments CallNumber List of integers Port Atom call exit fail redo suspend wakeup error failmatch enterbody exitbody redobody trymatch failbody Goal Term VariableNames List with the format Name Variable Name Atom Variable Variable Hints This predicate is not part of the IF Prolog runtime system and is therefore not available for applications intended for third parties Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also trace 1 IF Prolog V5 3 579 Reference Manual Execution control Language construct true 0 Goal which is always true true The language construct true 0 succeeds exactly once Hints The language construct true 0 is not a predicate so it cannot be redefined The predicates current_predicate 1 and current_visible 2 do not indicate language constructs Explicit module qualification with 2 or 2 is not permitted for language constructs with the exception of call 1 Standard This language construct complies with the definition of the ISO standard for Prolog See also fail 0 Reference Manual 580 IF Prolog V5 3 tty_size 2 3 Predicate Screen control Query the screen
319. dicates write_term 2 3 with the option quoted true write_canon ical 1 2 writeq 1 2 and writeq_atom 2 ignore this format so that the re readability of terms is not impaired Example Output in g format user float_format F F lt ENTER gt F g 0 6 lt ENTER gt yes Reference Manual 254 IF Prolog V5 3 float _format 2 Predicate Input output for terms user write 1 0e5 nl lt ENTER gt write 1 0e6 nl lt ENTER gt 100000 1e 06 yes Output in e format user float_format _ e 20 5 lt ENTER gt write 0 544021437 nl lt ENTER gt 5 44021e 01 yes Output in f format user float_format _ f 10 8 lt ENTER gt write 5 44021734e 1 nl lt ENTER gt 0 54402173 yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also number_chars 2 write_term 2 3 write 1 2 IF Prolog V5 3 255 Reference Manual File processing Predicate flush_output 0 1 Flush the buffer of an output stream flush_output flush_output Stream The predicate flush_output 0 flushes the contents of the output buffer of the current output stream and clears the buffer The predicate flush_output 1 works in the same way for the specified output stream Stream Arguments Stream Stream system defined term or alias atom Exceptions instantiation_error The arg
320. dule 1 at the start of the end_module O 1 directive or at the end of a file If a body has already been loaded for Module it is completely deleted as soon the begin_ module 1 directive appears Arguments Module Atom name of a module Exceptions Errors in directives are detected with consult 1 reconsult 1 or compile 1 No exceptions are generated Instead only error messages are output on the current error output stream This directive can produce the following error messages instantiation_error The argument Module must not be a variable but a variable was specified type_error atom The argument Module must be an atom but is a term of another type existence_error module The argument Module is not the name of an existing module permission_error modify system_module The argument Module is the name of a system module System modules may not be modified IF Prolog V5 3 121 Reference Manual Module concept Directive begin_module 1 Hints The atom begin_module is defined as a prefix operator Directives are evaluated during consultation see consult 1 reconsult 1 or compi lation see compile 1 procmp command Standard The directive Module is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also module 1 end_module 0 1 import 1 2 export 1 reexport 1 2 meta 1 Reference Manual 122 IF Prolog V5 3 break 0 P
321. e IF Prolog V5 3 25 Reference Manual Overview by functionality Predicates nl Stream outtab Position outtab Stream Position peek_byte ByteCode peek_byte Stream ByteCode Character peek_char Stream Character CharCode peek_code Stream CharCode put_byte ByteCode put_byte Stream ByteCode put_char Char put_char Stream Char put _code CharCode Stream CharCode peek_char peek_code put_code skip_line skip_line Stream tab Number tab Stream Number Input output for terms char_conversion CharacterIn CharacterOut char_conversion CharacterIn CharacterOut current_char_ conversion CharacterIn CharacterOut current_op Priority Assoc Name float_format FormatOld FormatNew op Priority Assoc Names op Priority Assoc Names portray Stream Term print Term print Stream Term read Term read Stream Term read_error Line Number Output newline Position the cursor Position the cursor Input a byte Input a byte Input a character Input a character Input a character Input a character Output a byte Output a byte Output a character Output a character Output a character Output a character Skip an input line Skip an input line Move the cursor forward Move the cursor forward Define a character conversion Define a character conversion directive Information on character conversions
322. e domain_error arity The command set_trace_length 1 was called with an incorrect number of pa rameters Furthermore if an arithmetic expression is specified for the argument Length all the exceptions for is 2 can occur Hints This command is only available in the alpha interface of the debugger See also view_trace 0 Reference Manual 656 IF Prolog V5 3 skip 0 1 Debugger command Command interface Execute up to exit of a subsequent subgoal skip S skip Number s Number The skip 0 1 command is resumes the debugger session the debugger stops at the exit EXIT of the current Number th subgoal starting at the current subgoal and switches to interactive mode If Number is larger than the number of the remaining subgoals in the current clause the debugger is positioned after the last subgoal of the current clause it stops at the next subgoal of the parent clause If the current Number th subgoal fails the debugger stops at the exit FAIL ERROR of the subgoal involved The skip 0 command is equivalent to skip 0 Arguments Number Integer or integer expression Number gt 0 Exceptions instantiation_error The argument Number or a subterm must not be a variable but a variable was specified type_error integer The argument Number must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer
323. e type_error list The argument VarList must be a list but is a term of another type Reference Manual 90 IF Prolog V5 3 assertz_with_names 2 3 Predicate Database type_error assignment An element of VarList is not an assignment with the format Name Variable type_error atom The argument Name must be an atom but is a term of another type type_error variable The argument Variable must be a variable but is a term of another type Hints The predicates consult 1 and reconsult 1 use assertz_with_names 2 3 to insert clauses in the database if the Prolog flag debug has the value on The information about variables is used by listing 1 2 for example The predicate assertz_with_names 2 3 is a metapredicate and manipulates the data base in the calling module or in the specified Module Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also asserta_with names 2 3 clause_with names 3 retract_with names 2 3 assertz 1 2 listing 1 2 IF Prolog V5 3 91 Reference Manual Stream processing Predicate assign_alias 2 Define an alias for an input output stream assign_alias Alias Stream The predicate assign_alias 2 defines an alias Alias for the input output stream Stream An alias is an alternative name that can be used as an argument for all input output pred icates instead
324. e if an arithmetic expression is specified for the argument Number all the exceptions for is 2 can occur Hints Arithmetic expressions will only be evaluated if Atom is not instantiated Example user atom_number 140218 X lt ENTER gt IF Prolog V5 3 107 Reference Manual Term conversion Predicate atom_number 2 X 140218 lt ENTER gt yes user atom_number X 10 7 lt ENTER gt X 1 4285714285714286 lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1A The predicate generates an exception if the atom is not representable as a number See also atom_codes 2 atom_chars 2 number_codes 2 number_chars 2 Reference Manual 108 IF Prolog V5 3 atom_part 4 Predicate String processing Determine the subatom of an atom atom_part Atom Position Length SubAtom The predicate atom_part 4 unifies SubAtom with the part of Atom defined by Position and Length If Position is less than 1 or greater than the length of Atom then SubAtom is unified with the null atom The same applies if Length is less than 1 If Length is greater than the remaining length of Atom after Position then SubAtom is unified with the rest of Atom starting from Position Arguments Atom Atom Position Integer or integer expression Length Int
325. e view_module Module view_predicate view_predicate Predicate view_stops view_variable view_variable VariableName Jump commands Command back_clause back_parent back_subgoal error Error Info exit fail back_clause back_parent back_subgoal error Error Info exit fail Scrolling and paging Command FoF vv Short be bp err bec bp err Short Store or append field in file Logging passes through ports Display the goal box in the window Display the clause box in the window Display the goal or clause box in the history list Display the trace field in the window Show dynamic call chain Show dynamic call chain Display default values Display constraints Display list of predicates in module Display list of predicates in module Display listing of a predicate Display listing of a predicate Display explicit breakpoints Display variable constraints Display variable constraints Functionality Branch back to clause head Branch back to CALL port of parent goal Branch back to CALL port of subgoal Raise an exception Force current subgoal to succeed Force the current subgoal to fail Branch back to clause head Branch back to CALL port of parent goal Branch back to CALL port of subgoal Raise an exception Force current subgoal to succeed Force the current subgoal to fail Functionality Scroll line by line forwards IF Prolog V5 3 627 Reference Manual Overvi
326. e 1 calling_context 1 Reference Manual 350 IF Prolog V5 3 modify_mode 3 Predicate Database Query and set the modify mode of a predicate modify_mode Predicate Before After Module The predicate modify_mode 3 defines whether or not the predicate Predicate is modifiable i e whether its clauses in the database and its attributes may be manipulated Identification of the predicate is based on its visibility in the calling module or in the specified Module The argument Before is unified with the previously valid mode The modification mode is then set according to After Like C predicates built in predicates cannot be modified If After is on then the definition of Predicate can be dynamically modified and the predicate attributes can be modified off then the definition of Predicate and the predicate attributes cannot be modified The predicates for manipulating the database asserta 1 2 retract 1 2 etc may only manipulate predicates for which the modification mode is set to on except abolish 1 This normally applies only to predicates which have been declared with dynamic 1 or for which the Prolog flag debug was set to on when they were defined The predicate Predicate need not yet be defined This attribute is retained beyond abol ish 1 Arguments Predicate Structure with the format Functor Arity Before Atom on off After Atom on off Functor Atom Arity Integer 0 lt Arity
327. e C interface C Function PrologModule Get Prolog module include cpro h MODULE PrologModule STRING Name The function PrologModule checks if a module with the name Name exists and returns it The function returns NULL if the module Name is not defined within IF Prolog Arguments Name Character string Hints The predefined modules system and user are accessible by the global variables System Module and UserModule Module specifications are used to indicate explicitly the module context in which a predicate is to be executed See also PrologFetch PrologOpen QueryCreate Reference Manual 728 IF Prolog V5 3 PrologOpen C Function Passive C interface Create current Prolog goal include cpro h t_cursor PrologOpen MODULE Module TERM Goal TERM VarList The function PrologOpen creates an active Prolog goal This Prolog goal also becomes the current Prolog goal The goal to be prepared for execution is defined by the goal term Goal and VarList the list of the variables in Goal This can be the result of a preceding call of ParseProlog The goal can then be executed with PrologFetch in the module context Module The function returns the structure t_cursor with the information about the state of the active Prolog goal This information will be used as reference to the current goal A goal that was the current goal before the call of PrologOpen rem
328. e Goal is being executed and the name of the signal received can be unified with Signal execution of Goal is interrupted and the specified Handler is called After the Handler is successfully processed the interrupted attempt to execute Goal is resumed If Handler fails the exception error system_error error interrupt signal S goal G is activated implicitly for the incoming signal S and the interrupted goal G If a predicate implemented in C is interrupted the entry interrupted Predicate is added to the above mentioned list Arguments Goal Goal Signal Atom abort alarm interrupt pipe quit termination user_1 user_2 Handler Goal Exceptions instantiation_error The argument Goal or Handler must not be a variable but a variable was specified type_error atom The argument Signal must be a variable or an atom but is a term of another type instantiation_error The argument Goal or Handler must not be a variable but a variable was specified type_error callable The argument Goal or Handler must have the syntactical structure of a Prolog goal IF Prolog V5 3 505 Reference Manual Contexts Exceptions Predicate signal_handler 3 existence_error procedure In executing Goal or Handler a predicate was to be activated which is not defined and the Prolog flag unknown has the value error type_error atom The argument Goal or Handler or a subgoal has been qualified by means of 2 or 2 with a term th
329. e empty list TermUnifyUniversal Unify term with structure TermUnifyVar Unify terms 2 hes 4 2 He ee Rae a 9 Prolog syntax nis 9 2 9 3 9 4 9 5 Basic Prolog elements 4 4454 be ek ew PRE Ee EEE ERA Oe eS g2 Constants ea sca 445 43 24S eR oS Oe oie 24 Sed 28 Ged o2 ee ces ce Hh cas es Be gs SS ce oe BH eS eS Se Dita OUCIUTES 2s de oy kale oe he ee oe eg beg ee es He Bt Operators a Sek ee Ee eo Bs Se SS Oe Ee OE 9 3 1 Converting expressions into equivalent normal structures 9 3 2 _Listof built in Operators s lt ss scs ss ee eee EEE BS 9 3 3 Test and definition predicates i o s ses es eee eee ee Arithmetic expressions and functions o o oa o a e a a Prologi tek t o s patema es pa eR ioe RO ee ee e G a A ISO Standard Directives and Predicates B ASCII table xvii 793 793 798 799 804 808 813 813 818 820 820 821 825 827 C Glossary 831 Bibliography 835 Index 836 xviii Chapter 1 Introduction The IF Prolog system from Siemens AG Austria is an implementation of the ISO Prolog standard ISO International Standardization Organization This standard was prepared by ISO Working Group 17 comprising representatives from various national standardization bodies IF Prolog also contains interfaces and predicates which extend the language and ensure compatibility with earlier versions of the product The Standard dictates us to sup
330. e indicates the variable in the clause ClauseNumber to be monitored The atom bind or modify may be specified as the BindingType bind refers to the moni toring of the binding of the variable Monitored Variable to a term The binding type modify includes the functionality of bind but automatically extends the monitoring to include any variables in the bound term Explicit breakpoints The Breakpoint is defined by specifying a predicate indicator or a predicate indicator and clause number or a predicate indicator clause number and subgoal number The debugger checks whether the predicate has been defined when the breakpoint is set The ports at which the debugger is to stop in the relevant box is specified in the Ports argument One of the following atoms or a list of the following atoms may be specified as the port IF Prolog V5 3 661 Reference Manual Command interface Debugger command stop 4 stop_interactive 1 2 4 Port Abbreviation Meaning call c CALL port enterbody eb ENTERBODY port fail f FAIL port failbody fb FAILBODY port failmatch fm FAILMATCH port redo r REDO port redobody rb REDOBODY port suspend S SUSPEND port trymatch tm TRYMATCH port wakeup wW WAKEUP port exit X EXIT port exitbody xb EXITBODY port error er ERROR port The following designations may be used for frequently used combinations of ports Designation Meaning all all ports inner enterbody failbody failmatch redobody trymatch exitbody out
331. e objects If the file Filename exists and is readable this is the input file Otherwise if Filename does not already have a pro or ppp suffix the suffix pro will be appended to Filename This is then the name of input file The following flags are allowed on the command line a the output consists of functor name filename and search pattern default X output predicate name arity line number of first occurrence and file name This output can be used as a readable predicate index Exceptions Prolog exceptions from file access open read may occur existence error source_sink The input file does not exist permission error open source_sink The input file cannot be opened for reading Compatibility V5 1A The command protags is new Reference Manual 16 IF Prolog V5 3 proxref System command Prolog system Invoke the Prolog cross referencer proxref Flag Filename Filename The command proxref generates a list of predicates with their cross references from Prolog source files and outputs the list on standard output The list of cross references is either forward or backward chained A forward chained reference lists all predicates that are called in the body A backward chained reference lists from which predicate s a predicate is called If the file Filename exists and is readable this is the input file Otherwise if Filename does not already have a pro or ppp suffix th
332. e suffix pro will be appended to Filename This is then the name of input file The following flags are allowed on the command line a the output is in alphabetical order default u the output is in the order of occurrence in files f generate a forward chained reference list default p generate a forward chained reference list including builtin predicates b generate a backward chained reference list Exceptions Prolog exceptions from file access open read may occur existence error source_sink The input file does not exist permission error open source_sink The input file cannot be opened for reading Compatibility V5 1A The command proxref is new IF Prolog V5 3 17 Reference Manual Prolog system System command proxref Reference Manual 18 IF Prolog V5 3 Chapter 3 Overview by functionality of predicates This section contains an overview of the built in predicates arranged into groups according to their functionality It also includes the language constructs directives and special user defined predicates that can be used in the Prolog system The functor of each predicate is printed in bold type Each argument is preceded by one of the characters or symbolizing the call type of the argument see page 37 Predicates which allow backtracking are identified by the character before the functor Metapredicates are identified by the character be
333. e used for generating variable masks user append X Y Z lt ENTER gt X y _69 Z _69 lt ENTER gt X _125 y _69 Z _125 _69 lt ENTER gt X _125 _129 y _69 Z _125 _129 _69 lt ENTER gt X _125 _129 _133 Y _69 _125 _129 _133 _69 lt ENTER gt N Il yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also connect 3 member 2 IF Prolog V5 3 79 Reference Manual Term conversion Predicate arg 3 Access individual arguments of a structure arg Position Structure Argument The predicate arg 3 unifies Argument with the term of Structure at the argument position specified by Position If Position is 0 zero or greater than the arity of Structure the predicate fails The predicate can be used to extract arguments from structures and to instantiate as yet uninstantiated arguments of structures see examples Arguments Position Integer or integer expression Structure Structure Argument Term Exceptions instantiation_error The argument Position or Structure must not be a variable but a variable was specified type_error integer The argument Position must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer domain_error not_less_than_zero
334. e_error atom The argument After must be an atom but is a term of another type domain_error on_or_off The argument After must be one of the atoms on or off but is another atom type_error atom The argument Before must be a variable or an atom but is a term of another type domain_error on_or_off The argument Before must be a variable or one of the atoms on or off but is another atom permission_error access system_module The predicate predicate_mode 3 must not be executed for a system module Hints The exception mode is normally set to on only for predicates that were declared with dynamic 1 The predicate predicate_mode 3 is a metapredicate and manipulates the database in the calling module or in the specified Module A predicate may have certain attributes which when it is created are set implicitly by the system according to the current environment or declarations They can be modified to a certain extent explicitly by the user These include the following e List mode see list_mode 3 e Debug mode see debug_mode 3 e Exception mode see predicate_mode 3 e Modification mode see modify_mode 3 These attributes are retained even if the predicate is deleted with abolish 1 for ex ample Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso IF Prolog V5 3 407 Reference Manual Database Predicate predicate
335. eam must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error output stream The argument Stream is not a stream which has been opened for output open mode write or append Hints The terminal control predicates are implemented via the appropriate stream control functions of the device drivers see stream_control 2 The standard device drivers implement screen control via the terminfo termcap ser vice of the operating system They support only one terminal type for all output streams Reference Manual 146 IF Prolog V5 3 clear_eos 0 1 Predicate Screen control Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also clear_eol 0 1 clear_screen 0 1 IF Prolog V5 3 147 Reference Manual Screen control Predicate clear_screen 0 1 Clear screen clear_screen clear_screen Stream The predicate clear_screen 0O clears the entire screen connected to the current output stream The cursor is placed in the top left hand corner of the screen If
336. ecimal Meaning a T Bell Alert b 8 Backspace t 9 Horizontal tab n 10 Line feed v 11 Vertical tab f 12 Form feed r 13 Carriage return e 27 Escape ESC e If the backslash is followed by new line key the new line character ignored so that long atoms can be entered easily abc def equivalent to abcdef If the backslash is followed by an apostrophe the delimiter function of the apos trophe is disabled represents the apostrophe character has the same effect as a double apostrophe abc de fg equivalent to abc de fg To represent the printable character you have to disable the backslash by entering it twice h a equivalent to h a If the backslash is followed by up to three octal digits 0 7 and a further backslash this sequence is equivalent to the character with this character code The character code must be in the range 1 to 255 octal 377 In this way nonprintable characters can be represented abc 040 def equivalent to abc def Reference Manual 800 IF Prolog V5 3 Terms Prolog Syntax e If the backslash is followed by x two hexadecimal characters 0 9 a f A F anda further backslash this sequence is equivalent to the character with this character code The character code must be in the range 1 to 255 In this way nonprintable characters can be represented abc x64 ef
337. ecuting predicates in the context of the defining module All the metapredicates can be qualified in the call by an explicit definition of the module context in which they are to be executed see 2 For this they are implicitly passed an additional argument which contains the relevant module name For most predicates the context in which they are executed is not important but asserta 1 for example should normally enter facts and rules into the database in the module from which it was called and not in the module system where it is defined All the built in predicates which have module specific side effects such as asserta 1 2 which use module specific data such as write 1 2 or which themselves call goals such as findal1 3 are therefore defined as metapredicates Arguments PredicateList List with the format Predicate or structure with the format Predicate Predicate Structure with the format Functor Arity Functor Atom Arity Integer 0 lt Arity lt 127 Exceptions Errors in directives are detected with consult 1 reconsult 1 or compile 1 No exceptions are generated Instead only error messages are output on the current error output stream This directive can produce the following error messages IF Prolog V5 3 349 Reference Manual Module concept Directive meta 1 instantiation_error The argument PredicateList or a subterm must not be a variable but a variable was specified type_error list The argument
338. ed in PredicateList available for other modules The exported predicates must be made visible with import 1 2 The directives reexport 1 2 may only occur in the module interface Arguments Module Atom name of a module PredicateList List with the format Predicate or structure with the format Predicate Predicate Structure with the format Functor Arity Functor Atom Arity Integer 0 lt Arity lt 127 Exceptions Errors in directives are detected with consult 1 reconsult 1 or compile 1 No exceptions are generated Instead only error messages are output on the current error output stream This directive can produce the following error messages instantiation_error The argument Module or PredicateList or a subterm must not be a variable but a variable was specified type_error atom The argument Module must be an atom but is a term of another type existence_error module The argument Module is not the name of an existing module type_error list The argument PredicateList must be a regular list but is a term of another type or not regular Reference Manual 450 IF Prolog V5 3 reexport 1 2 Directive Module concept type_error predicate_indicator The argument Predicate in PredicateList must be a predicate indicator i e a structure with the format Functor Arity but is a term of another type type_error atom The name of the predicate Predicate in PredicateList must be an atom type_error integer
339. ed like structures with the arity 0 Arguments Term Term variable Functor Character string name of the structure Arity Integer 0 lt Arity lt 127 Pointers to term variables Exceptions instantiation_error The argument Term must not be a variable but a variable was specified type_error atom_or_compound The argument Term must be an atom or a structure but is a term of another type domain_error compound The argument Term is a structure but its functor or arity are not correct The following error causes IF Prolog to be exited implementation_error Arity arity out of range The argument Arity is not within the range 0 127 Example The following simple C function realizes a predicate indicator 1 which checks if a term is a predicate indicator i e a term of the form Functor Arity Reference Manual 750 IF Prolog V5 3 TermIsCompound C Function Active C interface include cpred h BOOLEAN indicator_1 void indicator Term TERM name arity long number STRING string return TermIsCompound PrologArg 1 2 amp name amp arity amp amp TermIsAtom name amp string amp amp TermIsInteger arity amp number void Cboot void CPRIM indicator 1 indicator_1 See also TermIsFunctor TermIsUniversal TermMakeCompound IF Prolog V5 3 751 Reference Manual Active C interface C Function TermlIsFloat Test for floating point number include
340. edicate which has not been declared as dynamic and therefore cannot be modified type_error list The argument VarList must be a variable or a list but is a term of another type type_error assignment An element of VarList is not an assignment with the format Name Variable type_error atom The argument Name must be a variable or an atom but is a term of another type type_error variable The argument Variable must be a variable but is a term of another type IF Prolog V5 3 461 Reference Manual Database Predicate retract_with_names 2 3 Hints If all clauses of a predicate are removed with retract_with_names 2 3 the predicate will remain defined but will always fail The predicate abolish 1 can be used to delete a predicate The predicate retract_with_names 2 3 is a metapredicate and manipulates the data base in the calling module or in the specified Module Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also abolish 1 asserta_with names 2 3 assertz_with_names 2 3 clause_with_names 2 3 retract 1 2 modify_mode 3 Reference Manual 462 IF Prolog V5 3 reverse 2 Predicate List processing Reverse a list reverse List ReversedList The predicate reverse 2 reverses List and unifies ReversedList with the reversed list Arguments List List ReversedList List Exception
341. efore depends on the interface IF Prolog V5 3 647 Reference Manual Command interface Debugger command nonstop 0 Continue without stopping nonstop no The nonstop 0 command is resumes the debugging session The debugger does not stop throughout subsequent execution until it reaches the last port before it exits It then switches to interactive mode Exceptions domain_error arity The command nonstop 0 was called with an incorrect number of parameters See also step 0 skip 0 1 continue 0 fast_skip 0 1 Reference Manual 648 IF Prolog V5 3 port 2 Debugger command Command interface Set debugger port p Ports Switch port Ports Switch The port 2 command can be used to set the debugger ports One of the following atoms or a list of the following atoms may be specified as the port s Port Abbreviation Meaning call c CALL port enterbody eb ENTERBODY port fail f FAIL port failbody fb FAILBODY port failmatch fm FAILMATCH port redo r REDO port redobody rb REDOBODY port suspend S SUSPEND port trymatch tm TRYMATCH port wakeup w WAKEUP port exit X EXIT port exitbody xb EXITBODY port error er ERROR port The following designations may be used for frequently used combinations of ports Designation Meaning all all ports inner enterbody failbody failmatch redobody trymatch exitbody outer call fail redo wakeup suspend exit error Arguments Ports Atom or list
342. eger or integer expression SubAtom Atom Exceptions instantiation_error The argument Atom Position or Length must not be a variable but a variable was specified type_error atom The argument Atom must be an atom but is a term of another type type_error integer The argument Position or Length must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer type_error atom The argument SubAtom must be a variable or an atom but is a term of another type Furthermore if an arithmetic expression is specified for the argument Position or Length all the exceptions for is 2 can occur Example user atom_part atom_part 6 4 P lt ENTER gt P part lt ENTER gt yes IF Prolog V5 3 109 Reference Manual String processing Predicate atom_part 4 Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also atom_concat 3 atom_prefix 3 atom_suffiix 3 getchar 3 index 3 sub_atom 5 atom_split 3 Reference Manual 110 IF Prolog V5 3 atom_prefix 3 Predicate String processing Determine the prefix of an atom atom_prefix Atom Length Prefix The predicate atom_prefix 3 unifies Prefix with the atom formed by the first Length char acters in Atom If Length is less than 1 Prefix is unified with the null atom
343. elimiter Subatoms atom_suffix Atom t Length Suffix byte_length Atom Length concat_atom List Atom concat_atom List Delimiter Atom current_language Language getchar Atom Position Character index Atom String Position lower_upper Lowercase Uppercase lower_upper Lowercase Uppercase match Mask Atom match Mask Atom Replacements match_atom List Atom match_atom List Atom parse_atom String StartPosition EndPosition Term VarList Error regexp RegExp Atom regexp RegExp Atom List sub_atom Atom StartLength Length RestLength SubAtom write_atom Term Atom write_formatted_atom Atom Format TermList writeq_atom Term Atom List processing append Head Tail List atom_chars Atom List atom_chars Atom List atom_codes Atom List atom_codes Atom List concat_atom List Atom Decompose an atom Determine the suffix of an atom Count the bytes in an atom Concatenate individual atoms to form an atom Concatenate individual atoms to form an atom with separators Query current language Access a character in an atom Determine the position of a character string in an atom Convert lowercase letters into uppercase Convert uppercase letters into lowercase Pattern matching Pattern matching Concatenate atoms to form an atom Concatenate matching atoms to form an atom Parse a character string
344. em and which cannot be prevented by Prolog e g C runtime stack overflows Arguments Term1 Term Term2 Term Hints The atom is built in as an infix operator Example The following example constructs a cyclic list which normally leads to endless loops on output In our example this is prevented by limiting the structure depth for output and by undoing the instantiation by means of the final fail 0 user a R R lt ENTER gt write_term R maxdepth 10 nl lt ENTER gt fail lt ENTER gt La a La a La a a a fa fa a 1 no The following examples demonstrate the normal behavior of 2 Reference Manual 58 IF Prolog V5 3 2 Predicate Term comparison user yes user yes user yes user yes Standard See also X a b lt ENTER gt a b lt ENTER gt X Y 3 4 lt ENTER gt 3 4 lt ENTER gt LA 3 7 B lt ENTER gt 7 3 lt ENTER gt a b A B lt ENTER gt a b lt ENTER gt unify with occurs check 2 2 2 2 Q 2 eyclic 1 This predicate complies with the definition of the ISO standard for Prolog IF Prolog V5 3 59 Reference Manual Term conversion Predicate 2 Convert between a structure and a list Structure List Structure List Structure List Structure List The predicate 2 converts
345. en 3 4 for reading or writing the redundant side of the pipe is closed automatically The predicate unix_make_pipe 1 is based on the C function pipe 2 see 10 This predicate is system dependent and may not be available on all operating systems Example See the example in the section Process management and communication in the IF Prolog User s Guide 2 Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Reference Manual 590 IF Prolog V5 3 unix_make_pipe 1 Predicate Stream processing See also open 3 4 close 1 2 unix_fork 1 exec 1 2 IF Prolog V5 3 591 Reference Manual Operating system Predicate unix_wait 1 2 Wait for termination of a child process unix_wait Pid unix_wait Pid ExitStatus The predicate unix_wait 1 suspends the current IF Prolog process until a direct child process terminates and then unifies Pid with the process ID number of that process In some circumstances incoming signals may interrupt this wait state as well even if such signals are handled by IF Prolog or the user Pid is unified with 1 in such cases The predicate unix_wait 2 acts in the same way as unix_wait 1 except that ExitStatus is additionally unified with the the exit status of the terminated child process Arguments Pid Integer ExitStatus Integer Exceptions system_error no_c
346. en Start and End and finally with End If Counter is already instantiated when the first call is made then a check is carried out to determine whether Counter lies in the range Start End If instantiated all the arguments are evaluated Arithmetic expressions which have to return an integer result can therefore be specified Arguments Start Integer or integer expression Counter Variable integer or integer expression End Integer or integer expression Exceptions instantiation_error The argument Start or End must not be a variable but a variable was specified type_error integer The argument Start or End must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer type_error integer The argument Counter must be a variable an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer Furthermore if an arithmetic expression is specified for the argument Start End or Counter all the exceptions for is 2 can occur Example In the simplest case the predicate for 3 generates a sequence of integers Reference Manual 258 IF Prolog V5 3 for 3 Predicate Arithmetic user for 2 X 9 write X tab 1 fail lt ENTER gt 23456789 no Integers in descending order can also be generated user for 2 X 3 write X tab 1 fail lt ENTER gt 210 1 2
347. ence_error procedure In executing Goal a predicate was to be activated which is not defined and the Prolog flag unknown has the value error type_error atom The argument Goal or a subgoal has been qualified by means of 2 or 2 with a term that is not an atom existence_error module The argument Goal or a subgoal is qualified by means of 2 or 2 with an atom that does not name an existing module Hints The predicate context 2 is a metapredicate and calls its goal in the calling module or in the specified Module The predicates activated in the goal must be visible in the calling module or in the specified Module unless the 2 qualification is used for such a predicate to indicate explicitly the module in which this predicate is visible The predicates activated in the goal are normally executed in the context of the module in which they are defined This does not apply to metapredicates which are executed in the context of calling module or the specified Module unless the 2 qualification is used for a metapredicate to indicate explicitly the module context in which this predicate is to be executed Example The following predicate defines a daemon which becomes active when the signal user_1 is received and on completion of the activity waits for further signals The daemon terminates when the signal user_2 is received daemon WorkGoal signal_control user_1 on signal_control user_2 on context sleep
348. ent is supplied with information that is set depending of the term type The function returns the following values TERM_VAR The term is an uninstantiated Prolog variable Info gt varno is supplied with a variable number Two variables possess the same number if they are identical Note Info gt varno loses its validity when a function is called which generates new terms or evaluates arithmetic expressions TERM_ATOM The term is a Prolog atom Info gt name is supplied with the name of the atom Note Info gt name loses its validity when no other term containing an atom or functor with this name can be accessed TERM_INTEGER The term is an integer within in the range of values for a C variable of the type signed long Info gt ivalue is supplied with the value of the number TERM_FLOAT The term is a floating point number Info gt rvalue is supplied with the value of the number TERM_COMPOUND The term is a structure Info gt compound functor is supplied with the name of the structure Info gt compound arity is supplied with the arity of the structure Note Info gt compound functor loses its validity when no other term containing an atom or functor with this name can be accessed TERM_OTHER The term has a type not listed above The contents of the structure Info is undefined Reference Manual 746 IF Prolog V5 3 TermDecompose C Function Active C interface Arguments Term Term variable Info Pointer to a
349. ent_socket 3 select 3 socket_accept 3 socket_bind 2 socket_connect 2 socket_close 1 socket_receive 2 3 socket_raw_receive 4 5 socket_send 2 3 socket_shutdown 1 2 Reference Manual 518 IF Prolog V5 3 socket_raw_receive 4 5 Predicate Net communication Receive data from socket socket_raw_receive Socket Size List Length socket_raw_receive Socket Size Addr List Length The predicates socket_raw_receive 4 5 receive data with buffer and length information from a socket The predicate socket_raw_receive 4 receives data from a connected socket see socket_connect 2 and socket_accept 3 The predicate socket_raw_receive 5 re ceives a datagram from any address The argument Socket must be a term representing a socket The argument Size must be a positive integer expression representing a buffer size for incoming data Data are only received up to this buffer size With a connected socket the remaining data sent from the same source if any may be received by a subsequent socket _ raw_receive 4 With a datagram socket the remaining data are discarded immediately The argument Addr of socket_raw_receive 5 is unified with the address from which data were received The address for internet domain socket has the form Host Port where Host is the name of the receiving machine and Port is the port number The address for unix domain socket is an atom Filename The argument List is unifie
350. er The entity read from the stream is not representable as a single character Standard These predicates comply with the definition of the ISO standard for Prolog Compatibility V5 0B ISO conformance exception permission_error input binary_stream is gen erated instead of permission_error input text_stream when the stream is not a text stream See also get_code 1 2 peek_byte 1 2 peek_char 1 2 Reference Manual 400 IF Prolog V5 3 phrase 2 Predicate Database Call a grammar rule phrase Goal List The predicate phrase 2 can be used to call a goal that has been generated from grammar rules The grammar rules are generated with the language construct gt 2 The argument Goal has been given as the left side of a grammar rule The argument List is unified by backtracking with all productions generated with the rule Arguments Goal Term List List Exceptions instantiation_error The argument Goal must not be a variable but a variable was specified type_error callable The argument Goal must have the syntactical structure of a Prolog goal existence_error procedure In executing Goal a predicate was to be activated which is not defined and the Prolog flag unknown has the value error type_error atom The argument Goal or a subgoal has been qualified by means of 2 or 2 with a term that is not an atom existence_error module The argument Goal or a subgoal is qualified by me
351. er call fail redo wakeup suspend exit error If stop_interactive Breakpoint is used the breakpoint is set at the call port Conditions enables the user to restrict further the criterion that determines whether the debugger is to stop at a breakpoint These conditions can be used to query a variable instantiation the instance tree depth and recursion depth can be used directly in integer expressions with the format Keyword Operator Value The keyword frequency is the number of passes through the breakpoint depth is the current search depth in the search tree and recursionis the recursion depth in the current search tree If the condition match Head is specified the debugger checks whether Head can be unified with the current subgoal If the condition match Head Body is specified the debugger also attempts to prove Body If the unification test for Head or proof of Body is not successful the breakpoint is ignored Unification with the clause head does not have any effect on the goal proving operation i e it cannot be used to instantiate variables in the goal being proved In the condition match Head Head refers to the specified subgoal if the Breakpoint is defined as PredicateIndicator ClauseNumber SubGoalNumber The debugger checks whether Body can in principle be unified with the specified subgoal in Breakpoint If this is not the case an error message domain_error is displayed and the breakpoint is not set
352. erefore lead to the first solution again The following steps can be followed after IF Prolog has been initialized with InitProlog 1 Call of ParseProlog in order to get a goal term 2 By means of PrologOpen this goal becomes the current goal and is therefore ready for execution 3 One or more calls of PrologFetch execute the goal The solutions may be analyzed with PrologGoal and the functions of the active C interface and may be processed further 4 The current goal is deactivated with PrologClose Arguments ActGoal Structure information on the current Prolog goal Hints Solutions can not be simultaneously searched for more than one goal However nested execution of queries is possible See also ParseProlog PrologClose PrologError PrologOpen QueryOpen Reference Manual 722 IF Prolog V5 3 PrologGoal C Function Passive C interface Prolog goal as term include cpro h TERM PrologGoal t_cursor ActGoal The function PrologGoal returns the current goal ActGoal as term After a successful execution this term contains the results as bound arguments Arguments ActGoal Structure information on the current Prolog goal See also PrologFetch PrologOpen QueryOpen IF Prolog V5 3 723 Reference Manual Passive C interface C Function PrologIsFloat Get floating point number from variable include cpro h BOOLEAN PrologIsFloa
353. erm from variable 727 PrologModule Get Prolog module 728 XV PrologOpen Create current Prolog goal 0 0 729 PrelogUnde Undo mniticaiion lt se a sa dee ed dew ed dee LES 730 QueryDispose Release passive Prolog goal 733 QueryOpen Activate a passive Prolog goal 734 sprintt Formatted output of Prolog terms and C data objects 735 StreamFlush Flush Prolog output buffer 736 StreamMode Query stream mode o oo a 737 TermAddList Add to a Prolog list lt u eest rernsieenasi eia 738 TermArg Access structure arguments osooso 740 TermCloseList Close a Prolog list 44 2286 ede dasad eS 741 TermCollect TermCollectSequence Release term variables 742 TermContext Determine current term context 745 TermDecompose Classify term 2 2 0 002000 000008 746 TermIsAton O Test ior aid i e oe hehe Roe ee eR REEDS 749 TermlsCompound Test for structure lt 4 464 64564642 e445 750 TermIsFloat Test for floating point number 752 TermIsFloatExpression Test for floating point expression 753 TermlePunctor Test for structure cce es se dai sa Sew Bek oo 754 TermIsInteger Test for integer aoaaa aaa a 756 TermIsIntegerExpression Test for integer expression T
354. erm of another type Hints The sequence of solutions is undefined if current_host 1 has several solutions for the current call Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also host_addr 2 net_service 3 socket 3 Reference Manual 180 IF Prolog V5 3 current _input 1 Predicate Stream processing Query current input stream current_input Stream The predicate current_input 1 unifies Stream with the current input stream Arguments Stream Stream system defined term Exceptions domain_error stream The argument Stream must be a variable or an input output stream supplied by open 3 4 Hints The predicate current_input 1 will never unify Stream with an alias or the filename that was possibly used with see 1 or open 4 Standard This predicate complies with the definition of the ISO standard for Prolog See also current_output 1 current_error 1 seeing 1 set_input 1 set_output 1 set_error 1 IF Prolog V5 3 181 Reference Manual Elementary input output Predicate current _language 1 Query current language current_language Language The predicate current_language 1 unifies Language with the current language The language can be set with the command line argument language It specifies which character set is supported for text streams If IF Prolo
355. error integer The argument Position must be an integer but is a term of another type domain_error not_less_than_zero The argument Position must be a positive integer but is negative type_error list The argument List must be a list but is a term of another type domain_error non_empty_list The argument List must be a non empty list but is empty Hints The first case of the predicate is semantically equivalent to the following definition Reference Manual 324 IF Prolog V5 3 list_nth 3 Predicate List processing list_nth 1 Element _ Element list_nth Position _ Rest Element Positioni is Position 1 list_nth Positionl Rest Element but is implemented more efficiently Example Query the third element of list user list_nth 3 c s c a X lt ENTER gt X c lt ENTER gt yes Instantiate the third element of list user list_nth 3 c b X c a lt ENTER gt X a lt ENTER gt yes Query position of an element user list_nth N b c a c c lt ENTER gt N 2 lt ENTER gt no Standard This predicate is not required by the ISO standard for Prolog available in ISO compatibility mode see Prolog flag iso Compatibility V5 1A The predicate list_nth 3 is new See also arg 3 member 2 memberchk 2 nonmember 2 list_last 2 Therefore it is not IF Prolog V5 3 325 Reference Manual Database Predicate listing 0 1 List the cl
356. error error_mask The argument Exception must be a structure with the format error _ _ but is a term of another type Hints The predicate exception_handler 3 is mapped to context 2 The predicate exception_handler 3 is a metapredicate and calls its goal in the calling module or in the specified Module The predicates activated in the goal must be visible in the calling module or in the specified Module unless the 2 qualification is used for such a predicate to indicate explicitly the module in which this predicate is visible The predicates activated in the goal are normally executed in the context of the module in which they are defined This does not apply to metapredicates which are executed in the context of calling module or the specified Module unless the 2 qualification is used for a metapredicate to indicate explicitly the module context in which this predicate is to be executed Example Define handling for all exceptions user exception_handler goal error E I catch_all error E I lt ENTER gt Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also call 1 context 2 exception 2 set_prolog flag 2 IF Prolog V5 3 237 Reference Manual Operating system Predicate exec 1 2 Overlay process exec Command exec Prog Args The predicate exec 1 starts an operating s
357. ert to uppercase 334 machine identification query 558 match pattern 338 341 regular expression 452 maximum function 309 maxint 309 memory database 309 global stack 309 local control stack 309 stacks 309 trail stack 309 memory management query parameters 183 set parameters 484 statistics 529 Reference Manual 840 IF Prolog V5 3 Index metapredicate declare 349 query module context 129 minimum function 309 minint 309 mod 309 module add a complex C function 708 add a simple C function 709 compile 155 conclude definition 225 declare metapredicates 349 declare predicates 413 define 354 define body 121 define current 479 define interface 354 delete 594 explicit specification 52 export predicates 241 import predicates 299 initialize 306 load 155 328 query current 175 query defined 184 reexport predicates 450 set call context 70 store in file 465 modulo function 309 multiplication 309 negation 71 368 newline output 362 normal structure 809 notational conventions 3 number binary 802 convert to atom 107 convert to character list 371 convert to list of character codes 374 fixed point 803 floating point 803 hexadecimal 802 octal 802 rational 804 syntax 801 test 370 numerical value calculate 309 occurs check 583 octal number syntax 802 operating system change drive 599 file information 273 query 560 query drive 600 oper
358. es of rational numbers 0r1 3 0r1256 1000000000 9 2 2 Variables In Prolog there are two different kinds of variables e Prolog variables These clearly differ in concept from variables in conventional programming languages Since this type of variable is the one most commonly used it will often be referred to simply as variable e Global variables These are identical in concept to variables in conventional programming languages such as C or Fortran Prolog variables A Prolog variable can be instantiated to any term regardless of whether the term is a constant a variable or a structure During goal execution Prolog variables are instantiated to terms by unification and therefore assume all the attributes of these terms This instantiation remains in force during goal execution and is not undone until backtracking takes place Any attempt to instantiate an already instantiated variable to another value will lead to the failure of the unification and will initiate backtracking to the last choice point If two variables are instantiated to each other they will be regarded as identical in subsequent processing user var X X a nonvar X atom X X a yes user X a var X no Reference Manual 804 IF Prolog V5 3 Terms Prolog Syntax user X Y X Y X Y X _100 Y _100 yes If a toplevel goal contains variables the associated variable instantiations if any will be output if the
359. es the result with List 2 Atom is uninstantiated List must be a completely instantiated list of character codes The predicate atom_ codes 2 uses List to create an atom the characters of which correspond to the char acter codes in List and unifies the result with Atom Arguments Atom Atom List List of integers or integer expressions Exceptions instantiation_error The argument List or a subterm must not be a variable but a variable was specified type_error list The argument List must be a list but is a term of another type type_error integer An element of List must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer representation_error character_code An element of List must be an integer representing a character code type_error atom The argument Atom must be an atom but is a term of another type Furthermore if an arithmetic expression is specified for an element in List all the exceptions for is 2 can occur Hints Integer expressions will only be evaluated if Atom is not instantiated IF Prolog V5 3 101 Reference Manual Term conversion Predicate atom_codes 2 Example user atom_codes hello X lt ENTER gt X 104 101 108 108 111 lt ENTER gt yes user atom_codes X 97 116 111 109 lt ENTER gt X atom lt ENTER gt yes List may be partially uninstantiated if Atom is instant
360. et or a stream opened for reading or opened for writing The predicate select 5 examines the sockets or streams in the list SocksOrStreams for readable or writable data Each stream element of SocksOrStreams must be a stream opened for reading or opened for writing The argument Timeout specifies the interval to wait for the selection to complete If Timeout is the atom off the predicate blocks i e waits infinitely until something is available or is interrupted If Timeout is zero the predicate polls the streams and returns immediately Otherwise Timeout must be a positive floating point number specifying the interval in seconds to wait if no socket or stream returns data The argument ReadyReadStreams resp ReadyReadSOS must be a variable It is instan tiated to the sublist of streams or sockets of Streams resp SocksOrStreams with readable data The argument ReadyWriteStreams resp ReadyWriteSOS must be a variable It is instan tiated to the sublist of streams or sockets of Streams resp SocksOrStreams with writable data If there is a timeout ReadyReadSOS resp ReadyWriteSOS is instantiated to the empty list The argument TimeLeft must be a variable It is instantiated to the remaining part of time left of the Timeout interval in seconds if a socket or stream returns earlier In default case TimeLeft returns zero Arguments Streams List of streams SocksOrStreams List of sockets or streams Timeout Positive floating point number
361. eturns several results e If ConditionGoal itself is a composite goal and if it contains a cut 0 then this cut will have no effect beyond the ConditionGoal If the new goal produced with gt 2 occurs as the first subgoal in a disjunction OR con struct 2 then 2 behaves differently This is similar to if then else constructs in other programming languages The new goal produced with gt 2 and 2 succeeds if either ConditionGoal and ThenGoal succeed or ConditionGoal fails and ElseGoal succeeds In procedural view this means that ConditionGoal is first executed If this is successful ThenGoal is executed and the composite goal succeeds if ThenGoal succeeds otherwise it fails If ConditionGoal fails ElseGoal is executed and the composite goal succeeds if ElseGoal succeeds otherwise it fails The subgoal ThenGoal is therefore only executed if ConditionGoal succeeds and ElseGoal is only executed if it fails By backtracking ThenGoal and ElseGoal can have several solutions Arguments ConditionGoal Goal ThenGoal Goal ElseGoal Goal IF Prolog V5 3 47 Reference Manual Execution control Language construct gt 2 Exceptions instantiation_error The argument ConditionGoal ThenGoal or ElseGoal must not be a variable but a variable was specified type_error callable The argument ConditionGoal ThenGoal or ElseGoal must have the syntactical structure of a Prolog goal existence_error procedure In exec
362. ew by functionality Debugger commands forward backward fast_forward fast_backward view_previous_screen lt view_last_screen lt lt view_next_screen gt view_first_screen gt gt forward backward fast_forward fast backward FF SR HR HE SHER HR SR HR HH HHH HR RHR RK view_previous_screen lt view_last_screen lt lt view_next_screen gt view_first_screen gt gt Scroll line by line backwards Scroll page by page forwards Scroll page by page backwards Scroll line by line forwards Scroll line by line backwards Scroll page by page forwards Scroll page by page backwards Display the previous goal or clause box Display the last goal or clause box stored Display the next goal or clause box Display the first goal or clause box stored Scroll line by line forwards Scroll line by line backwards Scroll page by page forwards Scroll page by page backwards Scroll line by line forwards Scroll line by line backwards Scroll page by page forwards Scroll page by page backwards Display the previous goal or clause box Display the last goal or clause box stored Display the next goal or clause box Display the first goal or clause box stored Reference Manual 628 IF Prolog V5 3 Chapter 6 Reference section on debugger commands This section contains descriptions of the commands of the debugger in alphabetical order A detailed description of debugger and examples can be found in the section
363. expression but is a term of another type or the result of the evaluation of the expression is not an integer representation_error character_code The argument CharCode must be an integer representing a character code Furthermore if an arithmetic expression is specified for the argument CharCode all the exceptions for is 2 can occur Hints Integer expressions for CharCode will only be evaluated if Character is not instantiated IF Prolog V5 3 133 Reference Manual Term conversion Predicate char_code 2 Example user char_code X 98 lt ENTER gt X b lt ENTER gt yes user char_code A Y lt ENTER gt Y 65 lt ENTER gt yes Standard This predicate complies with the definition of the ISO standard for Prolog The use of arithmetic expressions in the argument CharCode is not allowed in the ISO standard for Prolog In the ISO compatibility mode see Prolog flag iso therefore no arithmetic expressions may be used as arguments for this predicate Instead an evaluation must be programmed explicitly with the help of is 2 if necessary See also atom_codes 2 Reference Manual 134 IF Prolog V5 3 char_conversion 2 Predicate Input output for terms Define a character conversion char_conversion CharacterIn CharacterOut The predicate char_conversion 2 defines a character conversion A character conversion specifies that when reading terms each character Characte
364. expressions may be used as arguments for these predicates Instead an evaluation must be programmed explicitly with the help of is 2 if necessary Compatibility V5 0B Inconsistency in the ISO standard has been fixed exception type_error list or representation_error character _code is generated instead of domain _ error character_code_list when the argument List is not a list of char acter codes See also atom_codes 2 number_chars 2 char_code 2 Reference Manual 376 IF Prolog V5 3 once 1 Predicate Execution control Activate a goal once only once Goal Module The predicate once 1 behaves like cal1 1 but cannot be backtracked even if the specified Goal is re executable Arguments Goal Goal Exceptions instantiation_error The argument Goal must not be a variable but a variable was specified type_error callable The argument Goal must have the syntactical structure of a Prolog goal existence_error procedure In executing Goal a predicate was to be activated which is not defined and the Prolog flag unknown has the value error type_error atom The argument Goal or a subgoal has been qualified by means of 2 or 2 with a term that is not an atom existence_error module The argument Goal or a subgoal is qualified by means of 2 or 2 with an atom that does not name an existing module Hints The predicate once 1 is a metapredicate and calls its goal in the calling m
365. f a process ID number greater than zero is specified for Pid the signal is sent to precisely that process If 0 is specified for Pid the signal is sent to all processes that belong to the same process group as the current Prolog process Other special interpretations of Pid can be obtained from the description of the C function kil1 2 see 10 Arguments Pid Integer or integer expression Signal Atom integer or integer expression Exceptions instantiation_error The argument Pid or Signal or a subterm must not be a variable but a variable was specified type_error integer The argument Pid must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer Reference Manual 588 IF Prolog V5 3 unix_kill 2 Predicate Operating system type_error atom_or_integer The argument Signal must be an atom an integer or an integer expression but is a term of another type domain_error signal_name The argument Signal must be one of the built in signal names but is another atom Furthermore if an arithmetic expression is specified for the argument Pid or Signal all the exceptions for is 2 can occur Hints The predicate unix_kill 2 is based on the C function kill 2 see 10 This predicate is system dependent and may not be available on all operating systems Example user unix_getpid Pid lt ENTER gt unix_kill Pid interrupt lt ENTE
366. f it should be included in the system kernel Do you wish to use If another software product required by a package e g Informix or Motif has not been installed a warning message is printed and this package is not included e If a Prolog kernel name already exists the user is asked for confirmation to overwrite the old one If the user does not want to overwrite the kernel the system asks the user for a new name e The new kernel is linked A success or failure message is printed Exceptions IF Prolog Kernel name already exists There is already a file called name You have to install A product named in the message has to be installed before it can be linked to the Prolog kernel Re linking of IF Prolog Kernel name failed The new Prolog kernel could not be linked See also prolog Reference Manual 6 IF Prolog V5 3 procmp System command Prolog compiler Invoke the Prolog compiler procmp Option Filename The command procmp compiles the Prolog text contained in the file Filename The name of the compiled Prolog file is Name cmp Name is generated from the filename Filename by removing a possible suffix pro If a file Name cmp already exists it will be overwritten After a successful compilation the system invokes the command proopt to optimize the generated code The contents of the file Name cmp is similar to a saved system state see save_system 1 save_module 1 and can be loa
367. f term expected 9 too large constant 10 or expected 11 expected 12 gt or expected 13 or expected 14 illegal number 15 precedence error 16 expected 17 interrupt 18 i o error 19 illegal escape sequence 20 illegal character code 21 exceeded max_arity 22 unbound variable expected Arguments Number Integer or integer expression Message Atom Reference Manual 548 IF Prolog V5 3 syntax_error 2 Predicate Input output for terms Exceptions instantiation_error The argument Number must not be a variable but a variable was specified type_error integer The argument Number must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer type_error atom The argument Message must be a variable or an atom but is a term of another type Furthermore if an arithmetic expression is specified for the argument Number all the exceptions for is 2 can occur Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also read_error 2 3 read 1 2 read_term 2 3 IF Prolog V5 3 549 Reference Manual Operating system Predicate system 0 Start the operating system command interpreter system The predicate system 0 starts the operating system command interpreter whose program name path is defined in
368. fault error handling by IF Prolog If several contexts are nested the innermost context matching the corresponding context jump is used see section on Context jumps in IF Prolog User s Guide 2 If no matching context is found IF Prolog is exited with an error message The predicate break 0 Prolog input loop defines a context which matches all the context jumps initiated in the course of default error handling by IF Prolog 2 Exceptions Exceptions are raised by IF Prolog if errors have occurred However they can also be raised explicitly by the user exception 2 They are treated exactly as if they were exceptions raised by IF Prolog If there is information stored on how to handle the exception that has arisen for one of the active contexts searching takes place from the inside to the outside this exception handling is executed without the current search tree being discarded in the context Exception handling replaces the goal which raised the exception When it finishes execution is continued normally if no context jump is executed during the handling If an active context cannot be found which can handle the exception a context jump is automatically initiated by IF Prolog see section on Exceptions in IF Prolog User s Guide 2 3 Signals Signals are external events One of the ways in which signals can be dealt with is active handling by the application see section on Signals in IF Prolog User s Guide 2 If t
369. fference consists precisely of the atom bark This grammar is correct although it is by no means complete However you can see from it how to parse sentences user sentence dogs bark lt ENTER gt yes As you can see the mechanism can also be used to generate sentences even though this grammar is so small that it contains only one sentence user sentence X lt ENTER gt X dogs bark lt ENTER gt no IF Prolog V5 3 45 Reference Manual Database Language construct gt 2 Standard This language construct is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also expand_term 2 phrase 2 Reference Manual 46 IF Prolog V5 3 gt 2 Language construct Execution control IF THEN conjunction of goals ConditionGoal gt ThenGoal gt ConditionGoal ThenGoal ConditionGoal gt ThenGoal ElIseGoal 3 gt ConditionGoal ThenGoal ElseGoal The language construct gt 2 is used to combine two goals to form a new goal The new goal succeeds if both ConditionGoal and ThenGoal succeed ThenGoal will be executed only if ConditionGoal succeeds In contrast to 2 ConditionGoal is executed in a special way e Backtracking by ConditionGoal is not possible The composite goal can therefore only return several results if ConditionGoal succeeds and ThenGoal r
370. following predicates could be used to skip comments IF Prolog V5 3 507 Reference Manual Elementary input output Predicate skip_line 0 1 user read T skip_line read N lt ENTER gt gabba Comment lt ENTER gt next_line lt ENTER gt T gabba N next_line lt ENTER gt yes Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also get_char 1 2 get_until 3 4 Reference Manual 508 IF Prolog V5 3 socket 3 Predicate Net communication Create communication socket socket Domain Type Socket The predicate socket 3 creates an endpoint for communication The argument Domain specifies the communications domain within which communication will take place If Domain is unix communication uses UNIX protocols and is possible only between processes running on the same machine If Domain is internet communication uses DARPA Internet protocols and is also possible between processes running on different machines Prolog allows up to 64 sockets existing simultaneously The argument Type specifies the semantics of the communication If Type is datagram communication is based on connectionless unreliable messages of a fixed typically small maximum length If Type is stream communication is based on sequenced reliable two way connection based byte streams A stream socket must be in a
371. for equal to relationship user X 8 Y 8 0000 X Y lt ENTER gt X 8 Y 8 lt ENTER gt yes Testing two numbers for not equal to relationship user X 12 Y 10 X Y lt ENTER gt X 12 Y 10 lt ENTER gt yes Standard These predicates comply with the definition of the ISO standard for Prolog The set of permissible arithmetic expressions is an extension of the set of expressions prescribed by the ISO standard see is 2 See also is 2 op 3 IF Prolog V5 3 57 Reference Manual Term comparison Predicate 2 Unify terms Terml Term2 Terml Term2 The predicate 2 unifies Term1 with Term2 If neither term contains a variable then 2 is equivalent to the term comparison 2 For normal unification the Prolog system does not perform an occurs check in other words the system does not check whether one of the terms to be unified contains the other as a subterm Any attempt to unify such a term will either result in a endless loop in the Prolog system or produce cyclical structures Cyclical terms are output with a special notation Endless loops in the Prolog system do not necessarily result in an exception e g with resource_error and controlled exit since garbage collection and dynamic stack adjust ment mean that memory bottlenecks are not inevitable It is therefore possible for program crashes to occur which are based in the C runtime syst
372. for the underlying operating system The predicate get_socket_option 3 can be used to test the current setting of options Option Explanation Type of Value broadcast Transmit broadcast messages on off close_on_exec Control take over of current sockets on off debug Record debugging information on off dontroute Routing bypass for outgoing messages on off keepalive Keep connections alive on off nonblocking Make socket asynchroneous synchroneous on off oobinline Reception of out of band data on off linger Linger on close if data present integer revbuf Size of input buffer integer reuseaddr Local address reuse on off reuseport Local port reuse on off selectread Designate socket for reading on off selectwrite Designate socket for writing on off sndbuf Size of output buffer integer Arguments Socket Socket system defined term Option Atom Value Integer or atom on off Exceptions instantiation_error The argument Socket must not be a variable but a variable was specified type_error socket The argument Socket must be a socket supplied by socket 3 but is a term of another type IF Prolog V5 3 495 Reference Manual Net communication Predicate set_socket_option 3 domain_error socket The argument Socket must be a currently open socket supplied by socket 3 type_error atom The argument Option must be an atom but is a term of another type domain_error socket_option The argument Option is not in the
373. fore the functor Directives are identified by before the functor Predicates with functors that are defined as operators are shown in operator notation by default Term classification array TestTerm Test for array array Array Dimension Query dimension of an array atom TestTerm Test for atom atomic TestTerm Test for constant compound TestTerm Test for structure cyclic TestTerm Test for cyclic term digit Test Term Test for digit float TestTerm Test for floating point number ground TestTerm Test for ground instantiation integer TestTerm Test for integer 19 Overview by functionality Predicates letter TestTerm nonvar Test Term number TestTerm rational TestTerm var TestTerm Term comparison Terml Term2 Terml Term2 Terml Term2 Terml lt Term2 Terml gt Term2 Terml lt Term2 Terml gt Term2 Terml Term2 Terml Term2 Terml Term2 compare Op Term1 Term2 unify_with_occurs_check Term1 Term2 Term conversion Structure List Structure List arg Position Structure Argument atom_chars Atom List atom_chars Atom List atom_codes Atom List atom_codes Atom List atom_number Atom Number atom_number Atom Number char_code Character CharCode char_code Character CharCode copy_term Term1 Term2 Test for letter Test for instantiation Test for number Test for rat
374. g pang lt ENTER gt yes Reference Manual 342 IF Prolog V5 3 match_atom 2 Predicate String processing Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also match 2 3 regexp 2 3 concat_atom 2 3 IF Prolog V5 3 343 Reference Manual List processing Predicate member 2 List membership member Element List The predicate member 2 establishes the relationship between lists and their elements The following cases are possible 1 Element and List are instantiated the predicate member 2 checks whether Element is contained in List If so member 2 succeeds during backtracking as often as Element occurs in List Otherwise member 2 fails 2 Element is uninstantiated and List is instantiated member 2 fails if List is the empty list Otherwise when the goal is first executed the first element from List is instantiated to Element During each backtracking cycle Element is instantiated to the next element of List 3 Element is instantiated and List is uninstantiated the predicate member 2 unifies List in the first call with a list containing Element as its first element and a tail variable In each backtracking cycle Element appears as the second third etc element of List 4 Element and List are uninstantiated the predicate member 2 generates variable masks which fu
375. g point numbers at the time of the call and changes the format to that specified in FormatNew FormatNew must be a structure with two integer arguments L and P L specifies the minimum length of the output field If a negative value is specified for L the number is output left justified in the field if a positive value is specified the number is output right justified in the field P specifies the number of positions after the decimal point If P 0 then no decimal point is output The number to be output is rounded as appropriate The following structures are permissible as format specifications e L P Exponential notation i e the floating point number is output in the form d dddeSdd S is either or The exponent always has at least two digits E L P Same as e L P except that the character E is used to introduce the expo nent f L P The number is output as follows dddd ddd g L P The number is output in the form e L P if in this form the exponent is less than 4 or greater than the value of P Otherwise the number is output in the form f L P Trailing zeros are removed The decimal point is output only if it is followed by further digits L P Same as g L P except that the character E is used to introduce the expo nent The default setting for the output format is g 0 6 Arguments FormatOld Structure e L P L P g L P E L P G L P FormatNew Structure e L
376. g V5 3 435 Reference Manual Term conversion Predicate rational 3 yes user rational 7 Numer Denom lt ENTER gt Numer 7 Denom 1 lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also rational 1 is 2 operator rdiv Reference Manual 436 IF Prolog V5 3 read 1 2 Predicate Input output for terms Input a term read Term read Stream Term The predicate read 1 reads in a term from the current input stream and unifies it with Term The predicate read 2 acts in the same way as read 1 but reads from the specified input stream Stream If the end of the input stream is reached Term is unified with the atom end_of_file If a syntax error is detected when attempting to read in a valid Prolog term the behavior of read 1 2 is determined by the setting of the Prolog flag read_error see current_ prolog_flag 2 Arguments Stream Stream system defined term or alias atom Term Term Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream T
377. g has been configured with multiple octet characters following language specifi cations are supported ascii ASCII character set default euc EUC character set sjis SJIS character set chinese Chinese character set korean Korean character set taiwanese Taiwanese character set If IF Prolog has not been configured with multiple octet characters only the character set ascii is available Arguments Language Atom Exceptions type_error atom The argument Language must be a variable or an atom but is a term of another type Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Reference Manual 182 IF Prolog V5 3 current _memory_management 3 Predicate Memory management Query memory management parameters current_memory_management Area Parameter Value The predicate current_memory_management 3 unifies Area Parameter and Value by back tracking with the values assigned to one of the memory management parameters IF Prolog manages the memory areas database global constraints local trail and extension Each possesses the parameters minimal_size maximal_size minimal_gap maximal_gap default_gap and trace The values of all but the last parameter are positive integers The parameter trace has the value on or off Arguments Area Atom database global constraints local tra
378. g of characters The list of individual replacements is unified with L user match long a long_atom L lt ENTER gt L _ tom lt ENTER gt yes user match a abrakadabra L lt ENTER gt L brakadabra lt ENTER gt L abr kadabra lt ENTER gt L abrak dabra lt ENTER gt L abrakad bra lt ENTER gt L abrakadabr lt ENTER gt no The predicate suffix_pro Name New_Name checks whether Name contains pro as its extension If not this extension is added The result is unified with New_Name user listing lt ENTER gt user suffix_pro 2 suffix_pro Name Name match pro Name suffix_pro Name New_Name atom_concat Name pro New_Name IF Prolog V5 3 339 Reference Manual String processing Predicate match 2 3 yes user suffix_pro file F lt ENTER gt F file pro lt ENTER gt yes user suffix_pro file pro F lt ENTER gt F file pro lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also match_atom 2 regexp 2 3 Reference Manual 340 IF Prolog V5 3 match_atom 2 Predicate String processing Concatenate matching atoms to form an atom match_atom List Atom match_atom List Atom The predicate match_atom 2 su
379. gaia uranus for example gaia and uranus are the arguments A non negative integer representing the number of arguments in a structure A basic object incapable of further subdivision denoted by an identifier Proving method which in the event of a failed route in a blind alley returns to the last choice point in the proof tree and checks alternative paths Condition righthand part of a rule Model illustrating how Prolog proves a goal breadth first search Search strategy in proof trees which considers several paths built in predicate choice point clause compound term conjunction constant constraint consult context cut database simultaneously A predicate defined by the Prolog system Node in the proof tree at which multiple possibilities to satisfy or refute the goal exist Statement about objects and relations concerning objects a fact or a rule see structure Combination of statements A statement A B is true when both statements A and then B are true An atom or a number Restriction for the value of one or more variables To read in analyse and store in the database a Prolog text executing any directives Logical environment for the entire proof tree covered by the spec ified goal A built in predicate that removes choice points Set of predicates and all the objects managed by Prolog exclud ing Prolog stacks 831 Glossary Appendix C declaration part
380. ge_collection 1 Activate garbage collection garbage_collection Area The predicate garbage_collection 1 activates the garbage collection for the memory area Area IF Prolog manages the memory areas database global constraints local trail and extension In addition Area can be assigned the value all In this case garbage collection is performed in all memory areas Arguments Area Atom all database constraints global local trail extension Exceptions instantiation_error The argument Area must not be a variable but a variable was specified type_error atom The argument Area must be an atom but is a term of another type domain_error memory_area The argument Area must specify a memory area of the Prolog system The specified atom is not a valid identifier Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also set_memory_management 3 current memory management 3 Reference Manual 264 IF Prolog V5 3 get_array 3 Predicate Term classification Query array element get_array Array Index Term The predicate get_array 3 queries the element of Array whose index is Index and unifies the element with Term Arguments Array Array system defined term Index Positive integer Term Term Exceptions instantiation_error The argument Array or Index must not
381. getchar Atom Position Character The predicate getchar 3 unifies Character with the Positionth character in Atom If Position is greater than the length of Atom or less than 1 getchar 3 fails Arguments Atom Atom Position Integer or integer expression Character Character Exceptions instantiation_error The argument Atom or Position must not be a variable but a variable was specified type_error atom The argument Atom must be an atom but is a term of another type type_error integer The argument Position must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer type_error character The argument Character must be a variable or a character but is a term of another type Furthermore if an arithmetic expression is specified for the argument Position all the exceptions for is 2 can occur Example user getchar atom 2 C lt ENTER gt C t lt ENTER gt yes user getchar AbCdEfG 5 W lt ENTER gt W E lt ENTER gt yes IF Prolog V5 3 283 Reference Manual String processing Predicate getchar 3 user getchar word 100 C lt ENTER gt no Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also atom_concat 3 atom_part 4 atom_prefix 3 atom_suffix 3 index 3 sub_atom
382. gument Stream is not a stream which has been opened for output open mode write or append permission_error output text_stream The current output stream or the argument Stream must be a binary stream but is associated with a text stream type_error integer The argument ByteCode must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer representation_error byte The argument ByteCode must be an integer in the range 0 lt ByteCode lt 255 system_error write system_error close Reference Manual 428 IF Prolog V5 3 put_byte 1 2 Predicate Elementary input output system_error flush_output system_error interrupted The indicated error was reported by the operating system when writing on the output stream Stream Furthermore if an arithmetic expression is specified for the argument ByteCode all the exceptions for is 2 can occur Example Output of ASCII characters user put_code 97 put_code 98 put_code 10 lt ENTER gt ab yes Standard These predicates comply with the definition of the ISO standard for Prolog The use of arithmetic expressions in the argument ByteCode is not allowed in the ISO standard for Prolog In the ISO compatibility mode see Prolog flag iso therefore no arithmetic expressions may be used as arguments for this predicate Instead an evaluation must be programmed explicitly with the hel
383. gument VarList must be a list but is a term of another type Reference Manual 86 IF Prolog V5 3 asserta_with_names 2 3 Predicate Database type_error assignment An element of VarList is not an assignment with the format Name Variable type_error atom The argument Name must be an atom but is a term of another type type_error variable The argument Variable must be a variable but is a term of another type Hints The information about variables is used by listing 1 2 for example The predicate asserta_with_names 2 3 is a metapredicate and manipulates the data base in the calling module or in the specified Module Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also assertz_with names 2 3 clause with names 3 retract with names 2 3 asserta 1 2 modify_mode 3 listing 1 2 IF Prolog V5 3 87 Reference Manual Database Predicate assertz 1 2 Insert a clause in the database assertz Clause Module assertz Head Body Module The predicate assertz 1 inserts the specified Clause in the database in the calling module or in the specified Module as the new last clause of the associated predicate If the database does not contain the predicate in the module Module or if the Predicate is not visible in Module the predicate will be created in Module The p
384. have their normal significance Exactly the same character must occur in the corresponding position in Atom The predicate match 2 succeeds if Atom can be generated from Mask following the resolu tion of any pattern characters otherwise it fails The predicate match 3 acts in the same way as match 2 and if successful unifies Re placements with a list of all the characters or character strings generated from the pattern characters Since this assignment does not have to be unique a search can be carried out for further replacements by backtracking Arguments Mask Atom Atom Atom Replacements List of atoms Exceptions instantiation_error The argument Mask or Atom must not be a variable but a variable was specified type_error atom The argument Mask or Atom must be an atom but is a term of another type type_error list The argument Replacements must be a variable or a list but is a term of another type type_error atom An element of Replacements must be a variable or an atom but is a term of another type Reference Manual 338 IF Prolog V5 3 match 2 3 Predicate String processing Hints As Mask usually contains special characters it has to be enclosed in single quotes so that IF Prolog will recognize the string as an atom Example A question mark within Mask is replaced by precisely one character user match lon _a om long_atom lt ENTER gt yes The pattern character stands for any strin
385. he application handles signals actively see signal_control 2 and if there is information stored on how to handle the signal for one of the active contexts searching takes place from the inside to the outside the signal handling is executed without the current search tree being discarded as in the case of context jumps If handling is successful the goal execution interrupted by the signal is resumed as if the signal had not been received Otherwise or if a context cannot be found which can handle the signal the exception Reference Manual 166 IF Prolog V5 3 context 2 Language construct Contexts Exceptions error system_error error interrupt signal Signal is created The ContextInfo list can contain a number of entries for each of the context global actions When an appropriate event occurs the first set of information matching this event is used The following elements are valid in ContextInfo 1 catch CatchMask gt SubstituteGoal If throw 1 is called during execution within the context with a term which can be unified with CatchMask the entire context is rejected and the context 2 call replaced by SubstituteGoal 2 error Error Info gt Handler If an exception occurs within a context or if exception 2 is called and the information belonging to the exception see exception 2 can be unified with Error and Info then the goal which raised the exception is replaced by a copy of Handler and execution
386. he argument Goal must not be a variable but a variable was specified type_error callable The argument Goal must have the syntactical structure of a Prolog goal existence_error procedure In executing Goal a predicate was to be activated which is not defined and the Prolog flag unknown has the value error type_error atom The argument Goal or a subgoal has been qualified by means of 2 or 2 with a term that is not an atom existence_error module The argument Goal or a subgoal is qualified by means of 2 or 2 with an atom that does not name an existing module instantiation_error The argument Ports must not be a variable but a variable was specified type_error list The argument Ports must be a list but is a term of another type IF Prolog V5 3 415 Reference Manual Profiling Predicate profile 1 2 type_error atom An element of Ports must be an atom but is a term of another type Hints The profiling predicates are included in the module profiler This module must be imported before the predicates can be used These predicates are not part of the IF Prolog runtime system and are therefore not available for applications intended for third parties The predicate profile 1 2 is a metapredicate and calls its goal in the calling module or in the specified Module The predicates activated in the goal must be visible in the calling module or in the specified Module unless the 2 qualification is used for such a
387. he argument Stream must be associated with an open input output stream permission_error input stream The argument Stream is not a stream which has been opened for input open mode read permission_error input binary_stream The current input stream or the argument Stream must be a text stream but is associated with a binary stream permission_error past_end_of_stream The open option eof_action error was set for the input stream Stream and the end of the stream has already been reached system_error read IF Prolog V5 3 437 Reference Manual Input output for terms Predicate read 1 2 system_error interrupted The error indicated was reported by the operating system when reading the input stream Stream syntax_error Syntax errors were detected during analysis of input All the syntax errors de scribed for syntax_error 2 can occur Hints The call read Stream Term is identical to read_term Stream Term If the read process is interrupted by a signal the predicate fails even if the signal is handled Example user read T lt ENTER gt a 3 x lt ENTER gt T a 3 f x lt ENTER gt yes user read T1 read T2 lt ENTER gt a b c that s it lt ENTER gt T1 a b c T2 that s it lt ENTER gt yes Standard These predicates comply with the definition of the ISO standard for Prolog Compatibility V5 0B ISO conformance exception per
388. he argument Stream specifies a file or a different I O medium that cannot be opened existence_error stream The argument Stream must be associated with an open input output stream Hints All output predicates which do not have an explicit stream argument refer to the current output stream This stream can always be addressed via the built in alias current_ output as well IF Prolog V5 3 565 Reference Manual Stream processing Predicate tell 1 Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also told 0 telling 1 set_output 1 error_tell 1 see 1 open 3 4 assign_alias 2 Reference Manual 566 IF Prolog V5 3 telling 1 Predicate Stream processing Query current output stream telling Stream The predicate telling 1 unifies Stream with the current output stream The current output stream may be a stream that was set with tell 1 or set_output 1 Arguments Stream Stream system defined term or alias atom Exceptions domain_error stream_or_alias The argument Stream must be a variable or an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream Hints The predicate telling 1 can unify Stream with an alias or the filename that was possibly used with tel1 1 or
389. he calling module or in the specified Module The argument Before is unified with the previously valid mode The debug mode is then set according to After The debug mode can only be changed for predicates for which the modification mode is set to on The built in predicates like C predicates can never be monitored If After is on then the predicate Predicate can be monitored i e subgoals of the predicate can also be investigated off then Predicate cannot be monitored The predicate Predicate need not yet be defined This attribute is retained beyond abol ish 1 Arguments Predicate Structure with the format Functor Arity Functor Atom Arity Integer 0 lt Arity lt 127 Before Atom on off After Atom on off Exceptions instantiation_error The argument Predicate or After or a subterm must not be a variable but a variable was specified type_error predicate_indicator The argument Predicate must be a predicate indicator i e a structure with the format Functor Arity but is a term of another type type_error atom The name of the predicate Predicate must be an atom Reference Manual 212 IF Prolog V5 3 debug_mode 3 Predicate Database type_error integer The arity of the predicate Predicate must be an integer domain_error not_less_then_zero The arity of the predicate Predicate must be a positive integer but is negative representation_error max_arity The arity of the predicate Predicate must
390. he formatting sequences define how the associated elements of TermList are to be output and the other characters are output without special treatment as with write 1 2 Each formatting sequence in Format is associated with exactly one argument in TermList in the order of its occurrence The number of terms in TermList must thus match the number of conversion sequences in Format precisely and the types of the associated terms must match the conversion sequences Conversion sequences are introduced with the character The specification is not a conversion sequence but stands for the character itself The general structure of a conversion sequence is as follows LFlags Field length Precision Type Except for Type all other entries may be omitted Several Flags may be specified The following Flags are available Prints the sign with numbers in all cases Left justified output within the Field length a9 Prints a space instead of the sign for positive numbers Canonical output the significance is explained under the individual argument types 0 Replaces leading spaces by 0 in the output of integers The Field length specifies the minimum field length required for the output of the associated argument Output is normally right justified in this field Precision defines the output precision of the corresponding argument in relation to the type of format The significance for specific format types is g
391. he module in which they are defined This does not apply to metapredicates which are executed in the context of calling module or the specified Module unless the 2 qualification is used for a metapredicate to indicate explicitly the module context in which this predicate is to be executed Standard This predicate complies with the definition of the ISO standard for Prolog See also call 1 throw 1 context 2 exception 2 set_prolog_flag 2 Reference Manual 132 IF Prolog V5 3 char_code 2 Predicate Term conversion Convert between a character and a character code char_code Character CharCode char_code Character CharCode The predicate char_code 2 converts a Character into a CharCode or vice versa The fol lowing cases are possible 1 Character is instantiated the character code of Character is determined and unified with CharCode 2 Character is uninstantiated the character corresponding to CharCode is formed and unified with Character Arguments Character Character CharCode Integer or integer expression Exceptions type_error character The argument Character must be a character but is a term of another type representation_error character The argument Character is not representable as a single character instantiation_error The argument CharCode must not be a variable but a variable was specified type_error integer The argument CharCode must be an integer or an integer
392. he value of the argument Flag is not a valid Prolog flag Hints The default settings for the Prolog flags consult debug prompt search_path and warnings can be modified by system parameters see system_parameters 1 when IF Prolog is started The values of the Prolog flags notty iso and signal can be set using the appropriate system parameters only when IF Prolog is started Example user current_prolog_flag F W lt ENTER gt write F write lt ENTER gt write W nl fail lt ENTER gt bounded false char_conversion on consult notify debug off float_max 1 79769e 308 float_min 4 94066e 324 integer_rounding_function toward_zero iso off max_arity 127 max_integer 2147483647 Min_integer 2147483648 notty off prompt off read_error error report_read_error on Signal on search_path undefined_predicate error warnings on no user current_prolog_flag consult _ lt ENTER gt yes user current_prolog_flag warnings on lt ENTER gt IF Prolog V5 3 195 Reference Manual System information Predicate current _prolog_flag 2 yes Standard This predicate complies with the definition of the ISO standard for Prolog The Prolog flags backtrace consult double_quotes extended_syntax float_max float_min iso nested_comments notty prompt read_error report_read_error search_path signal warnings and write_depth are not required by
393. hen the execution sequence is undefined Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also consult 1 reconsult 1 IF Prolog V5 3 51 Reference Manual Module concept Language construct ee Specify the module of the called predicate Module Predicate Module Predicate This notation indicates that execution of Predicate is to be based on its visibility in Module It is not necessary for Predicate to have been exported from this module or for Module to have been imported in the current module The definition of the same predicate in the current module or in another imported module is ignored Predicate must not be a language construct or a qualified predicate Arguments Module Atom name of a module Predicate Atom or structure Exceptions The possible errors relating to this notation are detected and reported by IF Prolog during interpretation of a goal cal1 1 or on insertion in the database asserta 1 2 etc Hints The atom is defined as an infix operator A predicate call cannot be qualified more than once with Standard This language construct is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also 2 call 1 module 1 import 1 2 export 1 reexport 1 2 Reference Manual
394. hen writing on the output stream Stream Furthermore if an arithmetic expression is specified for the argument CharCode all the exceptions for is 2 can occur Example Output of ASCII characters user put_code 97 put_code 98 put_code 10 lt ENTER gt ab yes Standard These predicates comply with the definition of the ISO standard for Prolog The use of arithmetic expressions in the argument CharCode is not allowed in the ISO standard for Prolog In the ISO compatibility mode see Prolog flag iso therefore no arithmetic expressions may be used as arguments for this predicate Instead an evaluation must be programmed explicitly with the help of is 2 if necessary Compatibility V5 0B ISO conformance exception permission_error output binary_stream is generated instead of permission_error output text stream when the stream is not a text stream See also get_code 1 1 put_byte 1 2 put_char 1 2 IF Prolog V5 3 433 Reference Manual Term classification Predicate rational 1 Test for rational number rational TestTerm The predicate rational 1 succeeds if TestTerm is a rational number but not an integer otherwise it fails Arguments Test Term Term Example user rational Or3 7 lt ENTER gt yes user X is Or1 6 Or1 5 Ori 4 Ori 3 Or1 2 lt ENTER gt rational X lt ENTER gt X 0r29 20 lt ENTER gt yes user rational 7 lt ENTER gt n
395. her and can be used in an application to control actions specific to the operating system Example user system_name Sys lt ENTER gt Sys Sun0s 5 3 lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also prolog_serial 1 prolog_version 1 proroot 1 system_hostid 1 Reference Manual 560 IF Prolog V5 3 system_parameters 1 Predicate System information Query system parameters from IF Prolog call system_parameters ParameterList The predicate system_parameters 1 unifies ParameterList with a list of all parameters which were specified on calling IF Prolog and identified as system parameters The first element of the list is the name under which IF Prolog was called System parameters are all the call parameters which at call time appear in the command line before the first parameter that is not one of the parameters listed below and which do not follow the special system parameter Some system parameters require an argument This argument must follow the system pa rameter in question as a separate command line argument Arguments ParameterList List of atoms Exceptions type_error list The argument ParameterList must be a variable or a list but is a term of another type type_error atom An element of ParameterList must be a variable or an atom
396. hich data was received The address for internet domain socket has the form Host Port where Host is the name of the receiving machine and Port is the port number The address for unix domain socket is an atom Filename The argument List is unified with a list of character codes If nothing has been received List will be unified with the empty list Arguments Socket Socket system defined term Addr Structure Host Port or atom Filename Host Atom Port Integer Filename Atom List List of integers Exceptions instantiation_error The argument Socket must not be a variable but a variable was specified type_error socket The argument Socket must be a socket supplied by socket 3 but is a term of another type domain_error socket The argument Socket must be a currently open socket supplied by socket 3 type_error host port The argument Addr must be a variable or a structure of the form Host Port but is a term of another type type_error atom The argument Host must be a variable or an atom but is a term of another type IF Prolog V5 3 521 Reference Manual Net communication Predicate socket_receive 2 3 type_error integer The argument Port must be a variable or an integer but is a term of another type type_error atom The argument Filename must be a variable or an atom but is a term of another type type_error list The argument List must be a variable or a list but is a term of another type St
397. hild The predicate unix_wait 1 2 cannot be executed since no child process exists type_error integer The argument Pid or ExitStatus must be a variable or an integer but is a term of another type Hints The predicates unix_wait 1 2 are based on the C function wait 2 see 10 This predicate is system dependent and may not be available on all operating systems Example The following predicate implements system 2 user listing lt ENTER gt h user my_system 2 my_system _ Stat unix_fork Pid Reference Manual 592 IF Prolog V5 3 unix_wait 1 2 Predicate Operating system Pid 0 I A repeat unix_wait Pid Res lt 3 Res Stat my_system Com _ yes unix_exec Com user my_system exit 7 End lt ENTER gt End yes 7 lt ENTER gt See also the example in the section Process management and communication in the IF Prolog User s Guide 2 Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also unix_fork 1 unix_getpid 1 unix_kill 2 IF Prolog V5 3 593 Reference Manual Module concept Predicate unload 1 Remove module from the database unload Module The predicate unload 1 removes all information in connection with the specified Module from the database If the specified Module was the cur
398. hile TermIsList list NULL amp list TermCollect context NULL return ErrorContextIsSet static BOOLEAN nth_element size_t n TERM list TERM tm TERMCONTEXT context TermContext TERM element Reference Manual 730 IF Prolog V5 3 PrologUndo C Function Active C interface size_t i for i 0 i lt n i if TermIsList list amp element amp list TermCollect context NULL return FALSE F TermCollect context element NULL tm element return TRUE COROUTINE element_of index state BEGIN END RESUME 1 label1 HASEPILOG state gt no 0 if proper_list PrologArg 2 FAIL while nth_element state gt no PrologArg 2 amp tm if TermUnify PrologArg 1 tm DETACH 1 label1 else PrologUndo void Cbhoot void CPRED element_of 2 element_of sizeof index IF Prolog V5 3 731 Reference Manual Passive C interface C Function QueryCreate include cpro h t_query QueryCreate MODULE Module TERM Goal TERM VarList The function QueryCreate creates a passive Prolog goal The function returns the struc ture t_query with the information about the active Prolog goal This data structure will be needed for future reference to the passive Prolog goal A passive Prolog goal is not executable after creation It can be later repeatedly activated by QueryOpen and then executed The passive g
399. iana_jones X lt ENTER gt no The cut which is normally called for the predicate likes prevents the instantiation of X to snake from being undone and thus prevents a search for alternatives in this case tiger Standard This language construct complies with the definition of the ISO standard for Prolog See also repeat 0 fail 0 true 0 IF Prolog V5 3 Al Reference Manual Execution control Language construct 2 Conjunction of goals Goall Goal2 Goall Goal2 The language construct 2 is used to combine two goals to form a composite goal The new goal succeeds if both Goall and Goal2 succeed Goal2 will be executed only if Goall succeeds If Goall or Goal2 are re executable they can return several results Backtracking takes place first in Goal2 and if that is not or no longer possible in Goall Goal2 will then be re executed if Goall succeeds Arguments Goall Goal Goal2 Goal Exceptions instantiation_error The argument Goall or Goal2 must not be a variable but a variable was specified type_error callable The argument Goall or Goal2 must have the syntactical structure of a Prolog goal existence_error procedure In executing Goall or Goal2 a predicate was to be activated which is not defined and the Prolog flag unknown has the value error type_error atom The argument Goall or Goal2 or a subgoal has been qualified by means of 2 or 2 with a term that is not a
400. iated user atom_codes abcd _ X 99 Y lt ENTER gt X 98 Y 100 lt ENTER gt yes Standard This predicate complies with the definition of the ISO standard for Prolog The use of arithmetic expressions in the argument List is not allowed in the ISO standard for Prolog In the ISO compatibility mode see Prolog flag iso therefore no arithmetic expressions may be used as arguments for this predicate Instead an evaluation must be programmed explicitly with the help of is 2 if necessary See also number_codes 2 atom_chars 2 char_code 2 Reference Manual 102 IF Prolog V5 3 atom_concat 3 Predicate String processing Compose or decompose an atom atom_concat Atoml Atom2 Atom3 atom_concat Atom1 Atom2 Atom3 The predicate atom_concat 3 succeeds if Atom3 is a concatenation of Atom1 and Atom2 A distinction is made between the following two cases 1 Atom3 is instantiated Atom1 and Atom2 are unified by backtracking with all the possible decompositions of Atom3 2 Atom3 is uninstantiated Atom3 is unified with the atom arising from the concatenation of Atom1 and Atom2 Arguments Atom1 Atom Atom2 Atom Atom3 Atom Exceptions instantiation_error The argument Atom1 Atom2 and Atom3 must not be a variable but a variable was specified type_error atom The argument Atom1 Atom2 or Atom3 must be an atom but is a term of another type Example user atom_concat abc
401. iated both Functor and Arity must be instantiated If Arity is 0 then Functor must be a constant and Structure is simply unified with Functor Otherwise Functor must be an atom and a structure is generated with the functor Functor and as many different variables as arguments as are specified by Arity Struc ture is unified with this generated structure 2 Structure is instantiated If Structure is a constant atom or number Functor is unified with this constant and Arity with 0 If Structure is a genuine structure Functor is unified with the functor of the structure and Arity with its arity Arguments Structure Structure or constant Functor Constant atom or number Arity Integer or integer expression 0 lt Arity lt 127 Exceptions instantiation_error The argument Functor or Arity must not be a variable but a variable was specified type_error atomic The argument Functor must be an atomic term but is a term of another type type_error atom The argument Functor must be an atom but is a term of another type type_error integer The argument Arity must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer representation_error max_arity The argument Arity must be an integer within the range 0 127 IF Prolog V5 3 261 Reference Manual Term conversion Predicate functor 3 domain_error not_less_than_zero The argument Arity
402. ible with the new definition permission_error create operator The argument Names specifies an existing operator that may not be redefined Hints Directives are evaluated during consultation see consult 1 reconsult 1 or compi lation see compile 1 procmp command Operator declarations take effect as soon as the directive is evaluated Standard The directive op 3 complies with the definition of the ISO standard for Prolog The use of arithmetic expressions in the argument Priority is not allowed in the ISO standard for Prolog In the ISO compatibility mode see Prolog flag iso therefore no arithmetic expressions may be used as arguments for this predicate Instead an evaluation must be programmed explicitly with the help of is 2 if necessary See also op 3 current_op 3 Reference Manual 384 IF Prolog V5 3 open 3 4 Predicate Stream processing Open an input output stream open DeviceAndName Mode Stream open DeviceAndName Mode Stream Options The predicate open 4 opens DeviceAndName for input or output in accordance with the specified Mode and Options If DeviceAndName is an atom a file is opened with this name Otherwise DeviceAndName must be a structure of the form Device Name where Device is the name of an installed device driver see stream_device 2 and Name is an atom that is used by the device driver for identification purposes Stream must be an uninstantiate
403. ically call a Prolog goal Generate a choice point Find selected solutions of a goal Goal which is always true Schedule alarm IF Prolog V5 3 31 Reference Manual Overview by functionality Predicates catch Goal CatchMask SubstituteGoal context Goal ContextInfo current_signal Signal Mode exception Error Info exception_handler Goal Exception Handler signal_control Signal Command signal_handler Goal Signal Handler throw Ball Debugger debug Goal debug_begin debug_config Parameter Old New debug_end debug_mode Predicate Before After Tracer profile Goal profile Goal Ports profile_reset profile_stat profile_stat List trace Goal trace_begin trace_config Parameter Old New trace_end trace_output CallNumber Port Goal VariableNames Intercept a context jump Create a context Query signals and modes Raise an exception Define local exception handling Control signal processing Define local signal handling Initiate a context jump Activate the debugger for a goal User defined debugger initialization Configure the debugger User defined termination of the debugger Query and set the debug mode of a predicate Activate profiling for a goal Activate profiling for a goal Reset profiling statistics Query profiling statistics Query profiling statistics Activate tracing for a goal User defined tracer ini
404. icate by backtracking with the predicate indicators of all the visible predicates in the calling module or in the specified Module The predicate current_predicate 1 succeeds by backtracking for all the predicates which were visible at the time of the first call even if they have since been deleted or if other definitions have been added logic update view Arguments Predicate Structure with the format Functor Arity Functor Atom Arity Integer 0 lt Arity lt 127 Exceptions permission_error access system_module The predicate current_predicate 1 must not be executed for a system module type_error predicate_indicator The argument Predicate must be a variable or a predicate indicator i e a structure with the format Functor Arity but is a term of another type Hints The predicate current_predicate 1 is a metapredicate and considers only predicate definitions which are visible in the calling module or in the specified Module The sequence of solutions is undefined if current_predicate 1 has several solutions for the current call Standard This predicate complies with the definition of the ISO standard for Prolog See also current _visible 2 predicate_type 2 Reference Manual 190 IF Prolog V5 3 current _prolog_flag 2 Predicate System information Query Prolog flags current_prolog_flag Flag Value The predicate current_prolog_flag 2 unifies Flag by backtracking with all the names of
405. ice_control The value of the argument Command is none of the values permitted for a device control command Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also current_device_control 3 stream_device 2 IF Prolog V5 3 217 Reference Manual Term classification Predicate digit 1 Test for digit digit TestTerm The predicate digit 1 succeeds if TestTerm is an atom consisting of a digit character otherwise it fails Arguments Test Term Term Example user digit 7 lt ENTER gt yes user digit 7 lt ENTER gt no Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also letter 1 number 1 number_chars 2 Reference Manual 218 IF Prolog V5 3 discontiguous 1 Directive Database Declare discontiguous predicate definition discontiguous PredicateList discontiguous PredicateList A predicate declared with the directive discontiguous 1 does not have to be defined textu ally in a single block i e its definition can be interrupted by the definition of other predicates The directive discontiguous 1 may only occur in the declaration part of a module body The first discontiguous 1 directive indicating a predicate must precede all clauses f
406. ich refers to the C predicate and takes the information in the error context into consideration See also ErrorContextClear ErrorContextIsSet ErrorContextSet Reference Manual 700 IF Prolog V5 3 ErrorContextIsSet C Function Active C interface Status of the error context include cpred h BOOLEAN ErrorContextIsSet void The function ErrorContextIsSet returns TRUE if the error context is set otherwise it returns FALSE Hints The error context is always cleared before a C predicate is called If a C predicate returns FALSE and the error context is set IF Prolog automatically initiates an excep tion which refers to the C predicate and takes the information in the error context into consideration Example The following simple C function realizes a predicate list_length 2 which determines the length of a regular list include cpred h static BOOLEAN list_len_2 void xx list_len List Length TERM tail long length 0 tail PrologArg 1 while TermIsList tail NULL amp tail length return ErrorContextIsSet amp amp TermUnifyInteger PrologArg 2 length void Cbhoot void CPRIM list_len 2 list_len_2 IF Prolog V5 3 701 Reference Manual Active C interface C Function ErrorContextIsSet See also ErrorContextClear ErrorContextGet ErrorContextSet Reference Manual 702 IF Prolog V5 3 ErrorContex
407. icit breakpoints are deactivated An integer or list of integers may be specified as the argument If a list is specified all the breakpoints included in the list are deactivated Arguments Numbers Integer or integer expression or a list of integers or integer ex pressions Exceptions instantiation_error The argument Numbers or a subterm must not be a variable but a variable was specified type_error integer_or_list The argument Numbers must be an integer an integer expression or a list of integers or integer expressions but is a term of another type or the result of the evaluation of the expression is not an integer domain_error not_less_than_zero The argument Numbers must be a positive integer but is negative existence_error stop The argument Numbers does not specify an existing breakpoint domain_error arity The command deactivate_stop 0 1 was called with an incorrect number of pa rameters Furthermore if an arithmetic expression is specified for the argument Numbers all the exceptions for is 2 can occur Hints Breakpoints can be reactivated with the activate_stop 0 1 command Reference Manual 640 IF Prolog V5 3 deactivate_stop 0 1 Debugger command Command interface See also activate_stop 0 1 remove_stop 0 1 stop 1 2 4 stop_interactive 1 2 4 view_stops 0 IF Prolog V5 3 641 Reference Manual Command interface Debugger command error 2 Raise an exception error Error Info
408. ided the special structure VAR see numbervars under write_term 2 3 was not used Example user writeq hello nl lt ENTER gt hello yes user writeq new nline nl lt ENTER gt new nline yes user writeq Robert s daughter nl lt ENTER gt gt Robert s daughter yes user writeq 3 7 8 3 nl lt ENTER gt 3 7 8 3 yes Standard These predicates comply with the definition of the ISO standard for Prolog See also write 1 2 write term 2 3 write_canonical 1 2 read_term 2 3 IF Prolog V5 3 619 Reference Manual Term conversion Predicate writeq_atom 2 Convert a term into an atom writeq_atom Term Atom The predicate writeg_atom 2 converts Term into an atom taking the operator definitions into account and unifies the result with Atom Conversion to an atom occurs as with writeq 1 i e special characters in atoms are handled according to Prolog syntax rules Arguments Term Term Atom Atom Exceptions type_error atom The argument Atom must be a variable or an atom but is a term of another type Hints The call writeq_atom Term Atom is identical to open string test write S writeq S Term stream_control S string Atom close S An atom created by writeq_atom 2 is generally suitable for re input e g with parse_ atom 6 provided the same operator definitions are used for input as a
409. il extension Parameter Atom minimal_size maximal_size minimal_gap maximal_ gap default_gap trace Value Integer Value gt 0 or atom Value on off Exceptions type_error atom The argument Area Parameter or Value must be a variable or an atom but is a term of another type type_error integer The argument Value must be a variable or an integer but is a term of another type Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also set_memory_management 3 garbage_collection 1 statistics 0 2 IF Prolog V5 3 183 Reference Manual Module concept Predicate current_module 1 Query modules current_module Module The predicate current_module 1 unifies Module by backtracking with all the module names known to IF Prolog There are a number of built in module names in IF Prolog which cannot be redefined by the user Module Meaning system Built in predicates system Further system modules motif Motif interface informix Informix interface const_ Constraint package modules Further names for additional interfaces of IF Prolog may be added The predicate current_module 1 succeeds by backtracking for all the modules which existed at the time of the first call even if they have since been deleted or others have been added logic update view Arguments Module Atom name
410. ils The argument List must be a list The predicate checks whether Element is unifiable with an element in List If no unifiable element is found the predicate succeeds It would be meaningless to instantiate Element in any way since there are infinitely many terms that do not occur in List The predicate should be used only when Element and List are sufficiently instantiated Arguments Element Term List List Exceptions type_error list The argument List must be a list but is a term of another type Hints The predicate is semantically equivalent to the following definition nonmember Element List not memberchk Flement List but is implemented more efficiently Example The simplest application involves a check as to whether an element is not contained in a list user nonmember x c s c a lt ENTER gt yes The list must not necessarily be ground instantiated As soon as a unifiable element is found the predicate fails Reference Manual 364 IF Prolog V5 3 nonmember 2 Predicate List processing user nonmember a c X y z no An empty list contains nothing user nonmember X lt ENTER gt X _154 yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1A The predicate nonmember 2 is new See also member 2 memberchk 2 IF Prolog
411. in or TermList The function TermCollect contains a list of optional parameters The list must end with NULL The optional parameters are pointers to term variables that are not to be released A vector TermList with N terms as the parameters is passed to the function TermCollect Sequence The terms included in TermList are not to be released Arguments Context Term context Prolog terms the last argument must be NULL N Integer number of terms in vector TermList TermList Vector consisting of the terms Exceptions The following errors cause IF Prolog to be exited implementation_error TermCollect illegal context The argument TermCollect is not a term context generated with TermContext implementation_error TermCollectSequence illegal context The argument TermCollectSequence is not a term context generated with Term Context Example The following C function displays a term in LISP notation The internally user term variables are released as soon as possible in order to save memory space include cpred h static void display_lisp TERM t Reference Manual 742 IF Prolog V5 3 TermCollect TermCollectSequence C Function Active C interface TERMINFO info TERMCONTEXT context ARITY argno switch TermDecompose t amp info case TERM_COMPOUND printt 4s info compound functor context TermContext for argno 1 argno lt info compound arity targno pri
412. in accordance with Prolog syntax Regular expression matching Regular expression matching Analyze an atom Convert a term into an atom Formatted output of terms Convert a term into an atom Append or decompose lists Decompose an atom into a list of characters Convert a list of characters into an atom Decompose an atom into a list of character codes Convert a list of character codes into an atom Concatenate individual atoms to form an atom Reference Manual 22 IF Prolog V5 3 Predicates Overview by functionality concat_atom List Delimiter Atom connect List Head Tail list_last Element List list_length List Length list_nth Position List Element match_atom List Atom match_atom List Atom member Element List memberchk Element List nonmember Element List number_chars Number List number_chars Number List number_codes Number List number_codes Number List remove Sublist List Remainder reverse List ReversedList sort List SortedList Arithmetic Value lt Value Value gt Value Value lt Value Value gt Value Value Value Value Value atom_number Atom Number for Start Counter End for Start Counter End Result is Expression Global variables current_global Name get_global Name Value Concatenate individual atoms to form an atom with separators Connect a head and a
413. in lists user append a b c Y no user member M a bl c M a M no It is not advisable to use such structures since they cannot be processed correctly by all predicates Converting structures into lists The predicate 2 univ enables you to convert structures into non empty lists and vice versa Reference Manual 812 IF Prolog V5 3 Operators Prolog Syntax user X write user_output abcdefgh call X abcdefgh X write user_output abcdefgh yes Examples of lists List Equivalent normal structure Lab Led 2 9 0 06 d 1 1 al b Lea I Big of c da 1 a B a 1 B 9 3 Operators Operators are atoms which were defined as operators by means of op 3 At the same time the operator type the operator precedence and the associativity of its arguments are defined The following section describes how the conversion of an expression to the equivalent normal structure is controlled by these operator attributes The section 9 3 2 List of built in operators provides an overview of the built in operators of the Prolog system The section Test and definition predicates on page 820 deals with points to be taken into account in the operator definition 9 3 1 Converting expressions into equivalent normal structures At declaration time the following attributes are defined for an operator e type e operator precedence e associativity of
414. ined at the time of the first call even if they have since been deleted or if other associations have been added logic update view Arguments Name Atom Exceptions type_error atom The argument Name must be a variable or an atom but is a term of another type Hints The sequence of solutions is undefined if current_global 1 has several solutions for the current call Global variables are always assigned to a module they can be neither exported nor imported In operations with global variables therefore only those global variables defined in the calling module or in the specified Module are taken into account Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also get_global 2 pop_global 2 push_global 2 set_global 2 unset_global 1 IF Prolog V5 3 179 Reference Manual Net communication Predicate current _host 1 Query names of current host current_host Host The predicate current_host 1 queries the name s of the current host The argument Host is unified by backtracking with the standard name and the alias names of the current host The names are obtained either from the name server named the NIS service or the hosts database on UNIX etc hosts or etc inet hosts Arguments Host Atom Exceptions type_error atom The argument Host must be a variable or an atom but is a t
415. ing point notation The associated argument in TermList must be an floating point number or an expression The exponent part is introduced with the character E In canonical output flag the number is represented with maximum precision This type is equivalent to f or e and selects the shorter of the two notations This type is equivalent to f or E and selects the shorter of the two notations Prints a character The associated argument in TermList must be a character Prints a string The associated argument in TermList must be an atom Reference Manual 608 IF Prolog V5 3 write_formatted 2 3 Predicate Formatted input output for terms n No output The associated argument in TermList should be a variable This argu ment is unified with the number of characters that have been output by write_ formatted 2 3 so far If the unification does not succeed output is aborted and the predicate write_formatted 2 3 fails t Outputs a term in the same way as write 1 2 q Outputs a term in the same way as writeq 1 2 W Outputs a term in the same way as writeq 1 2 but using the maximum depth set for the Prolog flag write_depth Canonical output flag of the term is identical to write_canonical 1 2 Arguments Format Atom TermList List of terms Stream Stream system defined term or alias atom Exceptions instantiation_error The argument Stream Format or TermList must not be a variable but a variable was specified domai
416. ings Input File pointer standard input Output File pointer standard output Error File pointer standard error Hints The call of this function is necessary for the use of the passive C interface See also EndProlog ParseProlog IF Prolog V5 3 707 Reference Manual Active C interface C Function MCPRED Add a complex C function to a module include cpred h void MCPRED STRING Module STRING Functor ARITY Arity CPREDFUN Function size_t Size The function MCPRED is used to incorporate the predicate Functor Arity into IF Prolog The predicate is implemented by the complex C function Function A complex function is re executable i e allows backtracking Size specifies the size in bytes of the data structure needed for built in backtracking The predicate is assigned to the module Module Arguments Module Character string Functor Character string Arity Integer 0 lt Arity lt 127 Function C Function Size Integer Hints The function MCPRED should be called from the C function Cboot which is executed at startup of IF Prolog A module cannot be defined by simply adding C functions The predicates can only be used as soon as the module interface is created See also Choot CPRED CPRIM MCPRIM Reference Manual 708 IF Prolog V5 3 MCPRIM C Function Active C interface Add a simple C function to a module include cpred h void MCPRIM STRIN
417. int or one of the breakpoints does not exist an error message is generated In this case none of the specified breakpoints are removed Arguments Numbers Integer or integer expression or a list of integers or integer ex pressions Numbers gt 0 Exceptions instantiation_error The argument Numbers or a subterm must not be a variable but a variable was specified type_error integer _or_list The argument Numbers must be an integer an integer expression or a list of integers or integer expressions but is a term of another type or the result of the evaluation of the expression is not an integer domain_error not_less_than_zero The argument Numbers must be a positive integer but is negative existence_error stop The argument Numbers does not specify an existing breakpoint domain_error arity The command remove_stop 0 1 was called with an incorrect number of parame ters Furthermore if an arithmetic expression is specified for the argument Numbers all the exceptions for is 2 can occur IF Prolog V5 3 651 Reference Manual Command interface Debugger command remove_stop 0 1 See also stop 1 2 4 stop_interactive 1 2 4 view_stops 0 activate_stop 0 1 deactivate_stop 0 1 Reference Manual 652 IF Prolog V5 3 set_debug_depth 1 Alpha interface Alpha interface Set structure depth set_debug_depth Depth sdd Depth The set_debug_depth 1 command is used to specify the structure depth
418. ional number Test for variable Unify terms Compare terms for identity Compare terms for unidentity Terml less than Term2 order of terms Terml greater than Term2 order of terms Terml less or equal Term2 order of terms Terml greater or equal Term2 order of terms Term1 equal Term2 order of terms Terml not equal Term2 order of terms Test for non unifiability Compare terms Unify terms with occurs check Convert a structure into a list Convert a list into a structure Access individual arguments of a structure Decompose an atom into a list of characters Convert a list of characters into an atom Decompose an atom into a list of character codes Convert a list of character codes into an atom Convert an atom into a number Convert a number into an atom Convert a character into a character code Convert a character code into a character Create a term copy Reference Manual 20 IF Prolog V5 3 Predicates Overview by functionality create_array Array Dimension functor Structure Functor Arity functor Structure Functor Arity get_array Array Index Term number_chars Number List number_chars Number List number_codes Number List number_codes Number List parse_atom String StartPosition EndPosition Term VarList Error rational Number Numerator Denominator reduce Level Term ReducedTerm set_array Array Index Term write_atom Term Ato
419. irst possible solution and ignores any alternatives user listing lt ENTER gt h user append_x 3 x IF Prolog V5 3 39 Reference Manual Execution control Language construct 1 0 append_x L L append_x H T L HIEL append_x T L EL yes user append_x X Y a b c lt ENTER gt X R Y a b c lt ENTER gt no In order to state that Indiana Jones likes all animals except snakes you could say that the relationship indiana_jones likes snake is to be evaluated with fail If the cut were to be omitted from the following program the second clause for likes 2 would be found after backtracking and the goal likes indiana_jones snake could be executed The cut prevents backtracking and specifies that likes indiana_jones snake can be executed either exactly once or as in this case due to fail not at all user listing lt ENTER gt xxx user animal 1 animal snake animal tiger xxx user likes 2 x x likes indiana_jones snake fail likes indiana_jones X animal X yes user likes indiana_jones snake lt ENTER gt no user likes indiana_jones tiger lt ENTER gt yes However this definition has its disadvantages If you ask whether indiana_jones likes anything you receive an answer which conflicts with that given above Reference Manual 40 IF Prolog V5 3 1 0 Language construct Execution control user likes ind
420. is continued The search tree in the context is not discarded 3 signal Signal gt Handler If during execution within the context a signal occurs for which active handling is to take place see signal_control 2 and its name can be unified with Signal execution is interrupted a copy of the goal Handler is called and if this goal succeeds the interrupted execution is resumed without the search tree being discarded in the context If execution of Handler fails the exception error system_error error interrupt signal Signal goal SubGoal is created If a predicate implemented in C is interrupted the entry interrupt ed Predicate is added to the above mentioned list In this case SubGoal contains the goal that would follow the interrupted predicate Arguments Goal Goal ContextInfo List Exceptions instantiation_error The argument ContextInfo or Goal must not be a variable but a variable was specified type_error list The argument ContextInfo must be a list but is a term of another type IF Prolog V5 3 167 Reference Manual Contexts Exceptions Language construct context 2 type_error context_indicator An element of ContextInfo must be a structure with the format Mask gt Handler but is a term of another type instantiation_error The argument Goal must not be a variable but a variable was specified type_error callable The argument Goal must have the syntactical structure of a Prolog goal exist
421. is not available in ISO compatibility mode see Prolog flag iso See also open 3 4 close 1 2 stream_control 2 current _stream_control 3 IF Prolog V5 3 537 Reference Manual Stream processing Predicate stream_device 2 Determine device name of an input output stream stream_device Stream Device The predicate stream_device 2 unifies Device with the name of the device driver associated with Stream The following device drivers are normally built into IF Prolog Device Usage file Operating system files standard Standard I O streams string Strings socket Sockets pipe Operating system pipes null Null device in UNIX equivalent to dev nu11 Some devices e g pipe null may not be available on all operating systems Arguments Stream Stream system defined term or alias atom Device Atom Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream type_error atom The argument Device must be a variable or an atom but is a term of another type Standard This predicate is not required by the ISO standard for Prol
422. is unified with the null atom If Length is greater than the length of Atom Suffix is unified with Atom Arguments Atom Atom Length Integer or integer expression Suffix Atom Exceptions instantiation_error The argument Atom or Length must not be a variable but a variable was specified type_error atom The argument Atom must be an atom but is a term of another type type_error integer The argument Length must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer type_error atom The argument Suffix must be a variable or an atom but is a term of another type Furthermore if an arithmetic expression is specified for the argument Length all the exceptions for is 2 can occur Example user atom_suffix file pro 3 S lt ENTER gt S pro lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso IF Prolog V5 3 115 Reference Manual String processing Predicate atom_sufhix 3 See also atom_concat 3 atom_prefix 3 atom_part 4 getchar 3 index 3 sub_atom 5 atom_split 3 Reference Manual 116 IF Prolog V5 3 atomic 1 Predicate Term classification Test for constant atomic TestTerm The predicate atomic 1 succeeds if TestTerm is a constant atom or number otherwise
423. ist of atoms the atoms in the list are defined or deleted as operators in the given order The operator is assigned the specified Priority which is represented by a positive integer between 1 and 1200 If a value of 0 is specified as the Priority the operator is deleted if it already exists The operator has the specified associativity Assoc If operators of the same precedence occur together Assoc determines how the operands are associated Assoc also determines whether the operator is a prefix an infix or a postfix operator The following atoms are used to specify the type fx Prefix non associative fy Prefix right associative xf Postfix non associative yf Postfix left associative xfx Infix non associative xfy Infix right associative yfx Infix left associative Arguments Priority Integer or integer expression 0 lt Priority lt 1200 Assoc Atom xf yf fx fy xfx xfy yfx Names Atom or list of atoms Exceptions instantiation_error The argument Priority Assoc or Names or a subterm must not be a variable but a variable was specified IF Prolog V5 3 379 Reference Manual Input output for terms Predicate op 3 type_error integer The argument Priority must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer domain_error operator_priority The argument Priority is not in the prescribed range of values for the preceden
424. it fails Arguments Test Term Term Example user atomic 5 240551 lt ENTER gt yes user X is 5 2 atomic X lt ENTER gt X 3 lt ENTER gt yes user atomic f a b lt ENTER gt no user atomic X lt ENTER gt no Standard This predicate complies with the definition of the ISO standard for Prolog See also atom 1 compound 1 cyclic 1 float 1 ground 1 integer 1 nonvar 1 number 1 rational 1 var 1 IF Prolog V5 3 117 Reference Manual Execution control Predicate bagof 3 Find selected solutions of a goal bagof Term Goal TermList Module The predicate bagof 3 unifies TermList with a list of all instantiations of Term with which Goal succeeds Term and Goal should share common variables Backtracking can take place by the variables which occur in Goal and not in Term known as free variables If bagof 3 succeeds the variables occurring both in Term and in Goal remain uninstantiated If Goal is specified as Terml Term2 SubGoal SubGoal is executed and the variables in Term1 Term2 are no longer considered free even if they occur only in Goal and not in Term Backtracking as described above does not therefore take place by these variables Arguments Term Term Goal Goal TermList List Termi Term SubGoal Goal Exceptions instantiation_error The argument Goal must not be a variable but a variable was specified ty
425. it goal Goall SYNTAX_ERROR exception syntax_error syntax_error Parm1 argno Argno culprit Culprit goal Goal SYSTEM_ERROR or invalid argument exception system_error error Parm1 argno Argno culprit Culprit goal Goal IF Prolog V5 3 703 Reference Manual Active C interface C Function ErrorContextSet If Argno is the value 0 the entry argno Argno is not added to the info list for the exceptions If Culprit is the value NULL the entry culprit Culprit is not added to the info list for the exceptions If Culprit is part of the error first argument of exception 2 and is the value NULL the atom unknown is used instead of Culprit The element goal Goal is created by IF Prolog Arguments Errorclass Element of ERRORCLASS see cpred h Parm1 Parm2 String Argno Integer 0 lt Argno lt Arity of the C predicate Culprit Erroneous term or NULL Hints The error context is always cleared before a C predicate is called If a C predicate returns FALSE and the error context is set IF Prolog automatically initiates an excep tion which refers to the C predicate and takes the information in the error context into consideration Example The following simple C function realizes a predicate month 2 which determines the name of a month according to its number include cpred h static BOOLEAN month_2 void month Number Name long number static const char names January Februa
426. it fails The predicate 2 succeeds if Term1 and Term2 are not identical otherwise it fails Unification does not take place so different variables are not identical Arguments Term1 Term Term2 Term Hints The atoms and are built in as infix operators Example Different variables cannot be identical user X Y lt ENTER gt no user _ _ lt ENTER gt yes user f X f Y lt ENTER gt no If a variable is instantiated to a term it is identical to that term user X Y X Y lt ENTER gt X _68 IF Prolog V5 3 63 Reference Manual Term comparison Predicate 2 2 Y _68 lt ENTER gt yes user X 4 Y 17 X lt ENTER gt Z 17 4 Y Z lt ENTER gt X 4 Y 17 4 Z 17 4 lt ENTER gt yes The next predicate not_in Term List checks whether a term has not yet occurred in the list user listing lt ENTER gt user not_in 2 not_in _ not_in T Head Tail Head T not_in T Tail yes user not_in 3 a b c lt ENTER gt yes user not_in A a b Z lt ENTER gt A _68 Z _69 lt ENTER gt yes Standard These predicates comply with the definition of the ISO standard for Prolog See also 9 2 04 2 O lt 2 OS 2 gt a Reference Manual 64 IF Prolog V5 3 lt 2 lt 2 gt 2 gt 2 Predicate Term comparison Compare terms Term Q lt Term
427. itch trace mode trace_port Ports Switch tp Set trace ports port Ports Switch p Set debugger ports set_debug_depth Depth sdd Set structure depth set_history Number sh Configure history set_trace_depth Depth std Set structure depth for trace outputs set_trace_length Length stl Set length of trace field trace Switch t a Switch trace mode trace_port Ports Switch tp Set trace ports Data manipulation Command Short Functionality unify Variable Value Unify variable unify Variable Value Unify variable Execution control Command Short Functionality continue c Continue to next breakpoint fast_skip fs Accelerate execution to exit of the subsequent subgoal fast_skip Number fs Accelerate execution to exit of a subsequent subgoal nonstop no Continue without stopping IF Prolog V5 3 625 Reference Manual Overview by functionality Debugger commands skip skip Number step continue fast _skip fast _skip Number nonstop skip skip Number step Display information Command help snapshot snapshot File snapshot File Mode trace view_and_box view_or_box view_history view_trace view_ancestors view _ancestors Number view_configuration view_constraints view_module view_module Module view_predicate view _predicate Predicate view_stops view_variable view _variable VariableName help snapshot snapshot File
428. ite or append Hints The terminal control predicates are implemented via the appropriate stream control functions of the device drivers see stream_control 2 The standard device drivers implement screen control via the terminfo termcap ser vice of the operating system They support only one terminal type for all output streams Reference Manual 144 IF Prolog V5 3 clear_eol 0 1 Predicate Screen control Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also clear_eos 0 1 clear_screen 0 1 IF Prolog V5 3 145 Reference Manual Screen control Predicate clear_eos 0 1 Clear to end of screen clear_eos clear_eos Stream The predicate clear_eos O clears the remainder of the screen connected to the current output stream starting at the cursor position The position where the cursor is currently located is also cleared If there is no screen connected to the current output stream or if the device driver for this output stream is not capable of executing this operation the predicate has no effect and the call succeeds nevertheless The predicate clear_eos 1 acts in the same way as clear_eos 0 but uses the screen connected to the specified output stream Stream Arguments Stream Stream system defined term or alias atom Exceptions instantiation_error The argument Str
429. iter of the subatoms and will not appear in Subatoms Arguments Atom Atom Delimiter Atom Subatoms List of atoms Exceptions instantiation_error The argument Atom or Delimiter must not be a variable but a variable was spec ified type_error atom The argument Atom or Delimiter must be an atom but is a term of another type type_error list The argument Subatoms must be a list but is a term of another type type_error atom An element of Subatoms must be a variable or an atom but is a term of another type Hints The predicate is the opposite of the predicate concat_atom 3 Example user atom_split var adm log FSCK L lt ENTER gt L var adm log FSCK yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso IF Prolog V5 3 113 Reference Manual String processing Predicate atom_split 3 Compatibility V5 1A The predicate atom_split 3 is new See also concat_atom 2 3 atom_concat 3 atom_part 4 atom_prefix 3 atom_suffix 3 getchar 3 index 3 sub_atom 5 Reference Manual 114 IF Prolog V5 3 atom_sufhix 3 Predicate String processing Determine the suffix of an atom atom_suffix Atom Length Suffix The predicate atom_suffix 3 unifies Suffix with the atom formed by the last Length char acters in Atom If Length is less than 1 Suffix
430. ith a term that is not an atom existence_error module The argument Goal or a subgoal is qualified by means of 2 or 2 with an atom that does not name an existing module IF Prolog V5 3 127 Reference Manual Execution control Language construct call 2 Hints The language construct call 2 is not a predicate so it cannot be redefined The predicates current_predicate 1 and current_visible 2 do not indicate language constructs Explicit module qualification with 2 is not permitted for this language construct The predicates activated in the goal must be visible in the calling module or in the specified Module unless the 2 qualification is used for such a predicate to indicate explicitly the module in which this predicate is visible The predicates activated in the goal are normally executed in the context of the module in which they are defined This does not apply to metapredicates which are executed in the context of the calling module or the specified Module unless the 2 qualification is used for a metapredicate to indicate explicitly the module context in which this predicate is to be executed Example user call member A a b lt ENTER gt A a lt ENTER gt A b lt ENTER gt no Standard This language construct is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also call 1 once 1 2 2 set prolog f
431. ition stream_control Stream Command stream_copy Stream1 Stream2 stream_device Stream Device stream_property Stream Info stream_type Stream StreamType tell Stream telling Stream told unix_make_pipe Pipename Operators current_op Priority Assoc Name op Priority Assoc Names op Priority Assoc Names Elementary input output at_end_of_line at_end_of_line Stream at_end_of_stream at_end_of_stream Stream get_byte ByteCode get_byte Stream ByteCode get_char Character get_char Stream Character get_code CharCode get_code Stream CharCode get_until SearchChar Text EndChar get_until Stream SearchChar Text EndChar nl Set current input stream Set current output stream Position within an input output stream Control an input output stream Redefine streams Determine device name of an input output stream Query information on input output streams Query type of an input output stream Set current output stream Query current output stream Reset current output stream Create a pipe Information on operators Define and delete operators Define and delete operators directive Query end of line Query end of line Query end of stream Query end of stream Input a byte Input a byte Input a character Input a character Input a character Input a character Read up to a specific character Read up to a specific character Output newlin
432. its goal in the calling module or in the specified Module The predicates activated in the goal must be visible in the calling module or in the specified Module unless the 2 qualification is used for such a predicate to indicate explicitly the module in which this predicate is visible The predicates activated in the goal are normally executed in the context of the module in which they are defined This does not apply to metapredicates which are executed in the context of calling module or the specified Module unless the 2 qualification is used for a metapredicate to indicate explicitly the module context in which this predicate is to be executed Example user if member A a b lt ENTER gt write A write else lt ENTER gt a A a lt ENTER gt b A b lt ENTER gt no user if member A a b lt ENTER gt Cwrite A fail write else lt ENTER gt ab no IF Prolog V5 3 297 Reference Manual Execution control Predicate if 3 user if member x a b lt ENTER gt write x write else lt ENTER gt else yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1A The predicate if 3 is new See also gt 2 2 0 call 1 2 2 set_prolog_flag 2 IF Prolog V5 3 Reference Manual 298 import 1 2 Directive Module concept
433. ity by backtracking with the information on the commands valid for Device to control stream independent de vices see device_control 2 This predicate provides a means of checking whether a device driver provides certain stream independent functionality Since IF Prolog can be equipped with any device drivers using its C driver interface it is always best before using device_control 2 to check whether the driver can in fact execute it Arguments Device Atom device driver name Command Atom Arity Integer 0 lt Arity lt 127 Exceptions instantiation_error The argument Device must not be a variable but a variable was specified type_error atom The argument Device must be an atom but is a term of another type domain_error device_name The value of the argument Device is not an existing device driver type_error atom The argument Command must be a variable or an atom but is a term of another type type_error integer The argument Arity must be a variable or an integer but is a term of another type domain_error not_less_than_zero The argument Arity must be a positive integer but is negative representation_error max_arity The argument Arity must be an integer within the range 0 127 Hints The sequence of solutions is undefined if current_device_control 3 has several so lutions for the current call Reference Manual 176 IF Prolog V5 3 current _device_control 3 Predicate Stream processing Standa
434. ivated which is not defined and the Prolog flag unknown has the value error type_error atom The argument Goal or a subgoal has been qualified by means of 2 or 2 with a term that is not an atom existence_error module The argument Goal or a subgoal is qualified by means of 2 or 2 with an atom that does not name an existing module Hints If trace 1 is called within trace 1 or debug 1 this call is ignored The predicate trace 1 is a metapredicate and calls its goal in the calling module or in the specified Module The predicates activated in the goal must be visible in the calling module or in the specified Module unless the 2 qualification is used for such a predicate to indicate explicitly the module in which this predicate is visible The predicates activated in the goal are normally executed in the context of the module in which they are defined This does not apply to metapredicates which are executed in IF Prolog V5 3 573 Reference Manual Tracing Predicate trace 1 the context of calling module or the specified Module unless the 2 qualification is used for a metapredicate to indicate explicitly the module context in which this predicate is to be executed This predicate is not part of the IF Prolog runtime system and is therefore not available for applications intended for third parties Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO co
435. iven below IF Prolog V5 3 607 Reference Manual Formatted input output for terms Predicate write_formatted 2 3 e E f s t q Number of significant positions Number of decimal places Maximum number of characters to be output Maximum term depth to be output The individual format types are as follows Prints an integer in decimal notation The associated argument in TermList must be an integer or an integer expression Prints an integer in octal notation The associated argument in TermList must be an integer or an integer expression In canonical output flag the number is preceded by 0 Prints an integer in hexadecimal notation The associated argument in TermList must be an integer or an integer expression In canonical output flag the number is preceded by Ox Prints an integer in hexadecimal notation The associated argument in TermList must be an integer or an integer expression In canonical output flag the number is preceded by OX Prints a floating point number in fixed point notation The associated argument in TermList must be an floating point number or an expression Prints a floating point number in floating point notation The associated argument in TermList must be an floating point number or an expression The exponent part is introduced with the character e In canonical output flag the number is represented with maximum precision Prints a floating point number in float
436. ket socket_bind Socket Addr socket_close QSocket socket_connect Socket QAddr socket_listen Socket socket_listen Socket Quelen socket_raw_receive Socket Size List Length socket_raw_receive Socket Size Addr List Length socket_receive Socket List Spawn process Query process ID of current process Send signal to a process Wait for termination of a child process Wait for termination of a child process Query names of current host Query communication sockets Get socket option Query host address Query host name Query communication service Synchronous input multiplexing Synchronous input multiplexing Synchronous input multiplexing Set socket option Create communication socket Accept a connection Bind a name to a socket Close a socket Connect a socket Listen for connections Listen for connections Receive data from socket Receive data from socket Receive data from socket IF Prolog V5 3 35 Reference Manual Overview by functionality Predicates socket _receive Socket Addr List Receive data from socket socket_send Socket List Send data to socket socket_send Socket Addr List Send data to socket socket_shutdown Socket Close a socket socket_shutdown Socket How Close a socket Reference Manual 36 IF Prolog V5 3 Chapter 4 Reference section for the predefined predicates This section contains descriptions of the built in predicates in
437. l pro user_input Stream lt ENTER gt close Stream lt ENTER gt Stream stream 7 lt ENTER gt yes user system cat example lt ENTER gt SiN p 1 joey 1327 May 29 15 33 heidi pro SfW r s gt 1 tommy 2396 Dec 11 10 45 ramona pro W p 1 marc 3923 Dec 11 10 45 sheena pro yes User inputs are counted by the command wc and the result is made available in IF Prolog as a number user system wc l echo user_input S lt ENTER gt read S Number lt ENTER gt line_1 lt ENTER gt line_2 lt ENTER gt line_3 lt ENTER gt lt EQF gt S stream 6 Number 3 lt ENTER gt yes The following predicate shows all Prolog source files which are present in the current directory Two commands are connected using a pipe for this purpose user listing lt ENTER gt h k user sources O x sources system 1s user_input Pipe system fgrep pro Pipe user_output close Pipe yes user sources lt ENTER gt yes Reference Manual 556 IF Prolog V5 3 system 3 5 Predicate Operating system example pro Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also system 0 1 2 open 3 4 unix_fork 1 exec 1 2 unix_kill 2 unix make_pipe 1 unix_wait 1 2 stream_control 2 IF Prolog V5 3 557 Reference Manual System information
438. l 714 IF Prolog V5 3 printt C Function Passive C interface Formatted output of Prolog terms and C data objects include cpro h size_t printt STRING Format The function printt is an extension of the C function printf see 10 for Prolog terms An argument in may be either a Prolog term or a normal C data object The arguments are printed in accordance with the formatting specifications in Format The output is printed on the standard output Arguments Format Character string format specification see write_formatted 2 3 Prolog terms or C data objects in accordance with Format See also outputlen fprintt sprintt write formatted 2 3 IF Prolog V5 3 715 Reference Manual Active C interface C Function PrologArg Access predicate arguments include cpred h TERM PrologArg ARITY Argno The function PrologArg returns the Argnoth argument of the active C predicate Arguments Argno Integer 1 lt Argno lt arity of the C predicate Exceptions The following errors cause IF Prolog to be exited implementation_error Argno argno out of range The argument Argno is not within the prescribed range of values Example The following simple C function realizes a predicate counter 1 which returns an integer number incremented by 1 at each call starting at 0 include cpred h BOOLEAN counter_1 void counter I
439. lag 2 Reference Manual 128 IF Prolog V5 3 calling_context 1 Language construct Module Query the module argument of metapredicates calling_context Module The control construct calling_context 1 queries the module argument of metapredicates The module argument is the argument that is made available explicitly or implicitly to meta predicates as an extra argument As a rule this argument is normally given the name of the module from which the metapredicate was called Arguments Module Atom name of a module Exceptions type_error atom The argument Module must be a variable or an atom but is a term of another type Standard This language construct is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also 2 meta 1 IF Prolog V5 3 129 Reference Manual Stream processing Predicate cancel_alias 1 Cancel an alias for an input output stream cancel_alias Alias The predicate cancel_alias 1 cancels the alias Alias of an input output stream This is done automatically when an input output stream is closed see close 1 The standard aliases see current_alias 2 cannot be canceled but cancel_alias 1 suc ceeds nevertheless Likewise cancel_alias 1 succeeds even if Alias is not a defined alias Arguments Alias Atom Exceptions instantiation_error The argument Alias must not be a vari
440. lay and an attempt is made to start the debug ger s Motif interface on this X display If this at tempt is not successful the value is automatically reset to alpha Arguments Parameter Atom see table above Old Term context dependent New Term context dependent Exceptions instantiation_error The argument Parameter or New or a subterm must not be a variable but a variable was specified type_error atom The argument Parameter must be an atom but is a term of another type domain_error config_option The argument Parameter is not a valid configuration parameter IF Prolog V5 3 209 Reference Manual Debugger Predicate debug_config 3 type_error integer The argument New must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer domain_error not_less_than_zero The argument New must be a positive integer but is negative type_error atom The argument New must be an atom but is a term of another type domain_error on_or_off The argument New must be one of the atoms on or off but is another atom domain_error display_option The value of the argument New is not a valid display specification Furthermore if an arithmetic expression is specified for the argument New all the exceptions for is 2 can occur Hints This predicate is not part of the IF Prolog runtime system and is therefore not available for applications inte
441. le 1 directive indicating a predicate must precede all clauses for this predicate Arguments PredicateList List with the format Predicate or structure with the format Predicate Predicate Structure with the format Functor Arity Functor Atom Arity Integer 0 lt Arity lt 127 Exceptions Errors in directives are detected with consult 1 reconsult 1 or compile 1 No exceptions are generated Instead only error messages are output on the current error output stream This directive can produce the following error messages instantiation_error The argument PredicateList or a subterm must not be a variable but a variable was specified type_error list The argument PredicateList must be a regular list but is a term of another type or not regular type_error predicate_indicator The argument Predicate in PredicateList must be a predicate indicator i e a structure with the format Functor Arity but is a term of another type type_error atom The name of the predicate Predicate in PredicateList must be an atom type_error integer The arity of the predicate Predicate in PredicateList must be an integer Reference Manual 358 IF Prolog V5 3 multifile 1 Directive Database domain_error not_less_then_zero The arity of the predicate Predicate in PredicateList must be a positive integer but is negative representation_error max_arity The arity of the predicate Predicate in PredicateList must be an integer in
442. les which occur in Goal and not in Term known as free variables If setof 3 succeeds the variables occurring both in Term and in Goal remain uninstantiated If Goal is specified as Terml Term2 SubGoal SubGoal is executed and the variables in Term1 Term2 are no longer considered free even if they occur only in Goal and not in Term Backtracking as described above does not therefore take place by these variables Arguments Term Term Goal Goal Term List List Termi Term SubGoal Goal Exceptions instantiation_error The argument Goal must not be a variable but a variable was specified type_error callable The argument Goal must have the syntactical structure of a Prolog goal existence_error procedure In executing Goal a predicate was to be activated which is not defined and the Prolog flag unknown has the value error type_error atom The argument Goal or a subgoal has been qualified by means of 2 or 2 with a term that is not an atom existence_error module The argument Goal or a subgoal is qualified by means of 2 or 2 with an atom that does not name an existing module IF Prolog V5 3 499 Reference Manual Execution control Predicate setof 3 type_error list The argument TermList must be a variable or a list but is a term of another type Hints The atom is defined as an infix operator The predicate setof 3 is a metapredicate and calls its goal in the calling module or in
443. leted after Filename has been processed When initialization directives are executed see init 1 any exception may arise These aborts the execution of the initialization goal but does not abort the load process In addition warnings are output as a function of the Prolog flag warnings in certain situations to alert you to possible sources of errors Hints If Filename does not contain the extension pro and if a file of this name cannot be found the extension pro is appended and the resultant filename used The predicate 2 is a metapredicate and manipulates the database in the calling module or in the specified Module If Filename contains module definitions then database manipulation takes place in these modules If not it is implicitly assumed that the contents of Filename belong to the body of the calling module or of the specified Module The difference compared with an explicitly specified body 1 directive at the start of Filename is that the associated body of the module is not first deleted If Filename contains only module interfaces and or bodies then consult 1 and recon sult 1 are prefectly identical The definition of a module interface of an existing module with the same name is first deleted and the definition of a module body overwrites an existing module body The init 1 directives in Filename are also executed in the context of the relevant module If a module in Filename contains several init 1 directives t
444. level see break 0 This applies to variable instantiations of a query and to exception messages The predicate write_formatted 2 3 takes this value in account if a term is to be output with the format 4w Arguments Flag Atom Value Atom integer or integer expression Reference Manual 490 IF Prolog V5 3 set_prolog_flag 2 Predicate System information Exceptions instantiation_error The argument Flag or Value must not be a variable but a variable was specified type_error atom The argument Flag must be an atom but is a term of another type domain_error prolog_flag The value of the argument Flag is not a valid Prolog flag domain_error flag_value The value of the argument Value is none of the values valid for a Prolog flag permission_error modify flag The argument Flag is the name of a Prolog flag the value of which may not be modified Hints The default settings for the Prolog flags consult debug prompt search_path and warnings can be modified by system parameters see system_parameters 1 when IF Prolog is started The values of the Prolog flags notty iso and signal can be set using the appropriate system parameters only when IF Prolog is started Example user set_prolog_flag consult notify lt ENTER gt yes user user lt ENTER gt lt EOF gt xxx consult user loaded in 0 00 sec yes user set_prolog_flag consult nonotify lt ENTER gt yes user user
445. level loop of IF Prolog alarm 1 Schedule a ou oe eK wa PO ee a ee OR ee E append 3 Append or decompose lists 2 0 0040004 arg 3 Access individual arguments of a structure artay 4 Test for ery lt ee sca ek kw ede ee eA ee ee ee we array 2 Query dimension of an array 02 02000 asserta 1 2 Insert a clause in the database asserta_with_names 2 3 Insert a clause in the database assertz 1 2 Insert a clause in the database assertz_with_names 2 3 Insert a clause in the database assign_alias 2 Define an alias for an input output stream at_end_of_line 0 1 Query end of line at_end_of_stream 0 1 Query end of stream avomy ll Test for atomi sa s kh waor Re Rede REE ERG REDE EOS atom_chars 2 Convert between an atom and individual characters atom_codes 2 Convert between an atom and individual character codes atom_concat 3 Compose or decompose an atom atom_length 2 Count the characters in an atom atom_number 2 Convert between an atom anda number atom_part 4 Determine the subatom of an atom atom_prefix 3 Determine the prefix of an atom atom_split 3 Decompose an atom 0 08 gt iv atom_suffix 3 Determine the suffix of an atom
446. lfill the member relationship Please note that due to the recursive structure of the predicate various combinations of the above four cases may occur Arguments Element Term List List Hints It is possible for the predicate member 2 to have an infinite number of solutions e g if it is called with two uninstantiated variables Calls such as member Y Y produce cyclic list structures which can lead to an endless loop if for example they are to be output Reference Manual 344 IF Prolog V5 3 member 2 Predicate List processing Example The simplest application involves a check as to whether an element is contained in a list user member a c s c a lt ENTER gt yes The predicate can also be used to query the elements of a list one at a time user member X a b c lt ENTER gt X a lt ENTER gt X b lt ENTER gt X c lt ENTER gt no In addition the predicate can generate variable masks as in the case of append 3 user member a L lt ENTER gt L a _113 lt ENTER gt L _112 a _115 lt ENTER gt L _112 _114 al_117 lt ENTER gt L _112 _114 _116 al_119 lt ENTER gt yes An empty list contains nothing user member X lt ENTER gt no Applications where both arguments are only partially instantiated are also possible user member f X a f Y c Z lt ENTER gt X _68 Y _68 Z _74 lt ENTER gt IF Pro
447. lies minint lt N lt maxint The values for minint and maxint can be accessed by means of the zero arity functions minint 0 and maxint 0 e g using the query user X is minint If the Prolog system has been configured with multiple precision integer support you can use integers outside this number range Character codes are also integers Reference Manual 802 IF Prolog V5 3 Terms Prolog Syntax user X is 0 a 1 char_code C X X 98 C pb yes user X is O n X 10 yes Examples of integers 1256 000000034 Oxa34f This is a hexadecimal number 001277 This is an octal number 0b1010 This is a binary number O a Character codes are integers 0 n Floating point numbers are sequences of decimal digits containing a decimal point or an exponent or both optionally preceded by a minus sign TUB HEHE eee N1 N2 exponent are sequence of digits If you enter a floating point number outside the value range it will be set to the nearest representable value Floating point format By using the predicate float_format 2 you can control the format which the Prolog system uses to output floating point numbers Examples of floating point numbers 22 99 1 0 123 45E10 21e 20 IF Prolog V5 3 803 Reference Manual Prolog Syntax Terms Rational numbers are marked by a predeeding Or Or sequence of digits sequence of digits Exampl
448. listing 0 1 List the clauses in the database 326 Toad 1 Load compiled Prolog text e e Seos pinsa oe HEE See ES 328 load_system 1 Restore the old system status ooa a 330 localtime 9 Determine the date and time a oaoa aa a 332 lower_upper 2 Convert between lowercase and uppercase letters 334 man al 0 1 Qu tp t manual pages lt e ssc ed eeo dteet RE REEDS 336 match 2 3 Pattern matching 2 s e se soes a p dte e KE ee E aa e 338 match_atom 2 Concatenate matching atoms to form an atom 341 member 2 List membership 2 2 6 eee see eee ee ee ewe 344 memberchk 2 List membership 2 265 ese ee ae ee 347 meta 1 Declare metapredicates 2 002 020000 349 modify_mode 3 Query and set the modify mode of a predicate module 1 Define amodule 224 bse seh ESE ERED EEE REE ES move_cursor 2 3 Position the cursor 2 2 44 eee ee eS multifile 1 Declare predicates as being scattered over several files net_service 3 Query communication service n1l 0 1 Output newline 2s ee ee Re A ee ee ER nonmember 2 List membership 2 244255 6 be bee wee es nonotify 0 Do not output load message lt so os cost sede ceuda nonvar 1 Test for instantiation s 24 2 aos e se Goie RR eR non i Negation through failure e ve a we s ee a ee A e a number i Test for MIMDET ec 24 444 tendat s RoE ne ES number_chars
449. log V5 3 345 Reference Manual List processing Predicate member 2 X _68 Y _71 Z f _68 _135 lt ENTER gt X 68 y 71 Z _134 f _68 _137 lt ENTER gt X _68 Y Ti Z _134 _136 f _68 _139 lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also memberchk 2 nonmember 2 append 3 connect 3 list_last 2 list nth 3 Reference Manual 346 IF Prolog V5 3 memberchk 2 Predicate List processing List membership memberchk Element List The predicate memberchk 2 succeeds if Element occurs in List otherwise it fails The following cases are possible 1 List is uninstantiated the predicate instantiates List to a list containing Element as its only element 2 List is instantiated the predicate checks whether Element is unifiable with an element in List The predicate should be used only when Element and List are sufficiently instantiated Arguments Element Term List List Exceptions type_error list The argument List must be a variable or a list but is a term of another type Hints The predicate is semantically equivalent to the following definition memberchk Element List member Element List but is implemented more efficiently Example The simplest application involves a check as to whether an element is contained in a list
450. log V5 3 581 Reference Manual Screen control Predicate tty_size 2 3 The standard device drivers implement screen control via the terminfo termcap ser vice of the operating system They support only one terminal type for all output streams Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also move_cursor 2 3 get_last 2 3 Reference Manual 582 IF Prolog V5 3 unify_with_occurs_check 2 Predicate Term comparison Unify terms with occurs check unify_with_occurs_check Term1 Term2 The predicate unify_with_occurs_check 2 unifies Term1 with Term2 after performing an occurs check This means that the system first checks whether either of the terms Term or Term2 contains the other as a subterm If this is true the unification fails This check is performed in each step of the unification Arguments Term1 Term Term2 Term Example A variable cannot be unified with a structure that contains the same variable user unify_with_occurs_check X 1 X lt ENTER gt no user unify_with_occurs_check 1 X X lt ENTER gt no user unify_with_occurs_check f X f g X lt ENTER gt no Standard This predicate complies with the definition of the ISO standard for Prolog See also 2 eyclic 1 IF Prolog V5 3 583 Reference Manual Operating system Predicate
451. lt ENTER gt Z lt ENTER gt Z a lt ENTER gt Z ab lt ENTER gt Z lt ENTER gt Z b lt ENTER gt Reference Manual 546 IF Prolog V5 3 sub_atom 5 Predicate String processing Z gt lt ENTER gt no Standard This predicate complies with the definition of the ISO standard for Prolog The use of arithmetic expressions in the arguments StartLength Length and RestLength is not allowed in the ISO standard for Prolog In the ISO compatibility mode see Prolog flag iso therefore no arithmetic expressions may be used as arguments for these predicates Instead an evaluation must be programmed explicitly with the help of is 2 if necessary See also atom_concat 3 atom_part 4 atom_prefix 3 atom_suffix 3 getchar 3 index 3 atom_split 3 IF Prolog V5 3 547 Reference Manual Input output for terms Predicate syntax_error 2 Assignment of syntax error number to error message syntax_error Number Message The predicate syntax_error 2 unifies Message with the syntax error message associated with Number If a Number for which no error message is known is specified Message is unified with the atom unknown syntax error The following syntax errors may occur Number Message 1 expected 2 expected 3 end of comment expected 4 illegal character 5 start of term expected 6 unknown stand alone character T operator expected 8 in postfix operator or end o
452. lue Floating point number Exceptions The following error causes IF Prolog to be exited implementation_error TermMakeFloat out of memory The function TermMakeFloat could not be executed successfully due to a lack of memory See also TermMakelnteger TermIsFloat IF Prolog V5 3 767 Reference Manual Active C interface C Function Term MakeFunctor Generate a Prolog structure include cpred h TERM TermMakeFunctor STRING Functor ARITY Arity The function TermMakeFunctor generates a Prolog structure with the name Functor and the arity Arity and returns it as the result A new Prolog variable is generated for each argument of the structure Arguments Functor Character string name of the structure Arity Integer 0 lt Arity lt 127 Exceptions The following errors cause IF Prolog to be exited implementation_error Arity arity out of range The argument Arity is not within the range 0 127 implementation_error TermMakeFunctor out of memory The function TermMakeFunctor could not be executed successfully due to a lack of memory Example The following simple C function realizes a predicate make_struct 3 which makes a structure with variables as arguments from given name and arity include cpred h BOOLEAN make_struct_3 void xx make_struct Functor Arity Structure STRING string long value return TermIsAtom PrologArg 1 amp string amp
453. m write_formatted_atom Atom Format TermList writeq_atom Term Atom String processing atom_chars Atom List atom_chars Atom List atom_codes Atom List atom_codes Atom List atom_concat Atom1 Atom2 Atom3 atom_concat Atom1 Atom2 Atom3 atom_length Atom Length atom_number Atom Number atom_number Atom Number atom_part Atom Position Length SubAtom atom_prefix Atom Length Prefix Create an array Generate a structure Analyze a structure Query array element Decompose a number into a list of characters Convert a list of characters into a number Decompose a number into a list of character codes Convert a list of character codes into a number Parse a character string in accordance with Prolog syntax Decompose a rational number Reduce the depth of a structure Set array element Convert a term into an atom Formatted output of terms Convert a term into an atom Decompose an atom into a list of characters Convert a list of characters into an atom Decompose an atom into a list of character codes Convert a list of character codes into an atom Decompose an atom Compose an atom Count the characters in an atom Convert an atom into a number Convert a number into an atom Determine the subatom of an atom Determine the prefix of an atom IF Prolog V5 3 21 Reference Manual Overview by functionality Predicates atom_split Atom D
454. m must be associated with an open input output stream permission_error input stream The argument Stream is not a stream which has been opened for input open mode read permission_error input text_stream The current input stream or the argument Stream must be a binary stream but is associated with a text stream permission_error past_end_of_stream The open option eof_action error was set for the input stream Stream and the end of the stream has already been reached system_error read ie neal The error indicated was reported by the operating system when reading the input stream Stream IF Prolog V5 3 395 Reference Manual Elementary input output Predicate peek_byte 1 2 type_error integer The argument ByteCode must be a variable or an integer but is a term of another type representation_error in_byte The argument ByteCode must be a variable or an integer in the range 1 lt Byte Code lt 255 Standard These predicates comply with the definition of the ISO standard for Prolog Compatibility V5 0B ISO conformance exception permission_error input text_stream is gen erated instead of permission_error input binary stream when the stream is not a binary stream See also get_byte 1 2 peek_char 1 2 peek_code 1 2 Reference Manual 396 IF Prolog V5 3 peek_char 1 2 Predicate Elementary input output Input a character peek_char Character peek_char Stream Character
455. m occurred type_error Type ErrorTerm An argument or subterm of an argument does not correspond with the ex pected type Problem Range Object Operation Flag Resource and Type are atoms that define the error type in more detail ErrorTerm is a term indicating the argument that triggered the error 2 Additional information Info Info is a list of terms of the type InfoName Value which supply error specific additional information InfoName is a ground term usually an atom and determines the type of additional information Value is any term The IF Prolog system can supply the following additional information IF Prolog V5 3 233 Reference Manual Contexts Exceptions Predicate exception 2 argno Value is the argument number of the term which triggered the error relating to the current Prolog goal see goal culprit Value is the term which triggered the error goal Value is the goal which triggered the error error Value is the atom which determines the type of system error e g could_not_ open signal Value is the name of the signal which triggered the error interrupted Value is the name of a predicate implemented in C that was interrupted by a signal valid_type Value is the type of term expected line Value is the input line number in case of syntax errors column Value is the input column number in case of syntax errors syntax_error Value is an atom that indicates the type of syntax error ba
456. mat Functor Arity Functor Atom Arity Integer 0 lt Arity lt 127 Exceptions Errors in directives are detected with consult 1 reconsult 1 or compile 1 No exceptions are generated Instead only error messages are output on the current error output stream This directive can produce the following error messages instantiation_error The argument PredicateList or a subterm must not be a variable but a variable was specified type_error list The argument PredicateList must be a regular list but is a term of another type or not regular type_error predicate_indicator The argument Predicate in PredicateList must be a predicate indicator i e a structure with the format Functor Arity but is a term of another type type_error atom The name of the predicate Predicate in PredicateList must be an atom type_error integer The arity of the predicate Predicate in PredicateList must be an integer IF Prolog V5 3 221 Reference Manual Database Directive dynamic 1 domain_error not_less_then_zero The arity of the predicate Predicate in PredicateList must be a positive integer but is negative representation_error max_arity The arity of the predicate Predicate in PredicateList must be an integer in the range 0 127 but is larger permission_error modify procedure The predicate indicator Predicate in PredicateList specifies a predicate which al ready exists and is not modifiable or which is the name of a language c
457. mber Number or arithmetic expression List List of characters Exceptions instantiation_error The argument List or a subterm must not be a variable but a variable was specified type_error list The argument List must be a list but is a term of another type type_error character An element of List must be a character but is a term of a another type syntax_error illegal number The characters in List do not represent a number type_error number The argument Number must be a number or an arithmetic expression but is a term of another type Furthermore if an arithmetic expression is specified for the argument Number all the exceptions for is 2 can occur IF Prolog V5 3 371 Reference Manual Term conversion Predicate number_chars 2 Hints The representation of floating point numbers does not depend on the floating point format currently set but on the maximum precision Example user number_chars 1234 X lt ENTER gt X SP 8 a lt ENTER gt yes The character list can also be in hexadecimal notation user number_chars X 0 x 1 F lt ENTER gt X 31 lt ENTER gt yes but user number_chars 31 0 x 1 F lt ENTER gt no Floating point numbers can also be processed user number_chars X 1 2 lt ENTER gt X 1 2 lt ENTER gt yes The conversion does not depend on the floating point format currently set
458. me pst is used This includes status information on the database global variables e operators modules In contrast to save_system 1 the saved status does not contain any data which may only be used by the development system e g break 0 debug 1 trace 1 The saved state can be subsequently restored by calling IF Prolog with the parameter r Filename or by using load_system 1 during a Prolog session Arguments Filename Atom Exceptions instantiation_error The argument Filename must not be a variable but a variable was specified type_error atom The argument Filename must be an atom but is a term of another type domain_error file_name The value of the argument Filename is not a valid name for a file permission_error open source_sink The argument Filename specifies a file or a different I O medium that cannot be opened system_error write system_error close system_error flush_output system_error interrupted The indicated error was reported by the operating system when writing on the output stream Filename IF Prolog V5 3 467 Reference Manual Database Predicate save_runtime 1 Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also save_system 1 load_system 1 save_module 1 Reference Manual 468 IF Prolog V5 3 save_system 1 Predicate Database Save current system st
459. ments Drivename Letter name of a drive Exceptions type_error character The argument Drivename must be a character but is a term of another type domain_error drive_name The value of the argument Drivename is not a valid drive character Hints To write code that should run under diverse operating systems you can use the predicate system_name 1 to determine the current operating system On operating systems that do not support the concept of drives this predicate is not available Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1A The predicate windows_getdrive 1 is new Windows This predicate is only available under Windows and OS 2 operating systems See also windows_chdrive 1 system name 1 chdir 1 getewd 1 Reference Manual 600 IF Prolog V5 3 write 1 2 Predicate Input output for terms Output a term write Term write Stream Term The predicate write 1 outputs Term on the current output stream Existing operator definitions are taken into account The predicate write 2 acts in the same way as write 1 but writes to the specified output stream Stream Both predicates output special characters from the term without special treatment Arguments Term Term Stream Stream system defined term or alias atom Exceptions instantiation_error The argume
460. mission_error input binary stream is gen erated instead of permission error input text_stream when the stream is not a text stream Reference Manual 438 IF Prolog V5 3 read 1 2 Predicate Input output for terms See also read_term 2 3 IF Prolog V5 3 439 Reference Manual Input output for terms Predicate read_error 2 3 Query position of a syntax error read_error Line Number read_error Line Column Number The predicate read_error 2 determines the number of the input line in which a syntax error was detected by the parser of IF Prolog in the last call to read 1 2 read_term 2 3 or parse_atom 6 and unifies the result with Line The number of the corresponding syntax error message is unified with Number The predicate read_error 3 additionally determines the character position of the error in the input line and unifies the result with Column Arguments Line Integer Column Integer Number Integer Exceptions type_error integer The argument Line Column or Number must be a variable or an integer but is a term of another type Example user read_term T syntax_errors quiet lt ENTER gt read_error A B C lt ENTER gt syntax_error C X lt ENTER gt atom lt ENTER gt _68 se QW Pe Il oN ol start of term expected lt ENTER gt yes Reference Manual 440 IF Prolog V5 3 read_error 2 3 Predicate Input output for terms
461. mmand is not implemented in the device driver type_error atom The argument StreamType must be a variable or an atom but is a term of another type Hints The predicate stream_type 2 is based on the control command stream_type 1 of the device drivers and can hence be used on I O streams of new device drivers as well provided the corresponding command is implemented in them Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also stream_control 2 stream_device 2 stream_property 2 Reference Manual 544 IF Prolog V5 3 sub_atom 5 Predicate String processing Analyze an atom sub_atom Atom StartLength Length RestLength SubAtom The predicate sub_atom 5 unifies SubAtom with all substrings of Atom by backtracking The predicate succeeds if SubAtom is a part of Atom beginning at the position StartLength and having the length Length Length is unified with the length of SubAtom StartLength with the length of the substring to the left of SubAtom and RestLength with the length of the substring to the right of SubAtom When the arguments StartLength Length and or RestLength are instantiated arithmetic expressions will be evaluated Arguments Atom Atom StartLength Integer or integer expression StartLength gt 0 Length Integer or integer expression Length gt 0 RestLength Integer or integer ex
462. module Module or if the Predicate is not visible in Module the predicate will be created in Module The predicate asserta 2 acts in the same way as asserta 1 but inserts the clause formed from Head and Body Head Body in the database Arguments Clause Structure atom Head Structure atom Body Term Exceptions instantiation_error The argument Head or Clause must not be a variable but a variable was specified type_error callable The argument Head Body or Clause must have the syntactical structure of a Prolog goal permission_error modify static_procedure The argument Head or the head of Clause specifies an existing predicate which has not been declared as dynamic and therefore cannot be modified permission_error access calling_context The argument Body or the body of Clause contains a call involving calling_con text 1 in a predicate that is not a metapredicate Hints The predicate asserta 1 2 is a metapredicate and manipulates the database in the calling module or in the specified Module Reference Manual 84 IF Prolog V5 3 asserta 1 2 Predicate Database Standard Only the predicate asserta 1 complies with the definition of the ISO standard for Prolog See also assertz 1 2 clause 2 retract 1 2 asserta_with names 1 2 modify_mode 3 IF Prolog V5 3 85 Reference Manual Database Predicate asserta_with_names 2 3 Insert a clause in the database asserta_with_names Clause VarList
463. mpatibility mode see Prolog flag iso See also call 1 trace_begin 0 trace_end 0 debug 1 trace_output 4 set_prolog_flag 2 Reference Manual 574 IF Prolog V5 3 trace_begin 0 User definable predicate Tracing User defined tracer initialization trace_begin Body The predicate trace_begin O is not a built in predicate but one which can be defined by the user It is called in the module in which trace 1 was called It is called automatically by trace 1 when tracing is started The user can define trace_begin 0 to perform preliminary activities such as defining default breakpoints with trace_config 3 when the tracer is started Hints Nested calls involving debug 1 and or trace 1 are ignored If trace 1 is called several times during a goal execution trace_begin O is called each time This predicate is not part of the IF Prolog runtime system and is therefore not available for applications intended for third parties Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also trace 1 trace_end 0 trace_config 3 IF Prolog V5 3 575 Reference Manual Tracing Predicate trace_config 3 Configure the tracer trace_config Parameter Old New The predicate trace_config 3 is used to query and modify trace parameters Parameter is used to specify the trace parameter to
464. mpatibility mode see Prolog flag iso See also current_predicate 1 IF Prolog V5 3 203 Reference Manual Term classification Predicate cyclic 1 Test for cyclic term cyclic TestTerm The predicate cyclic 1 succeeds if TestTerm is a cyclic term otherwise it fails Cyclic terms can be created with unification e g with the predicate 2 Arguments Test Term Term Example user cyclic a A A lt ENTER gt no user A s A cyclic A lt ENTER gt A _155 s _155 lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1A The predicate cyclic 1 is new See also 2 unify_with_occurs_check 2 atom 1 atomic 1 compound 1 float 1 ground 1 integer 1 nonvar 1 number 1 rational 1 var 1 Reference Manual 204 IF Prolog V5 3 debug 1 Predicate Debugger Activate the debugger for a goal debug Goal Module The predicate debug 1 activates the debugger for executing Goal Before Goal is executed the user defined predicate debug_begin O is called if it is visible in the calling module or in the specified Module After Goal has been executed the user defined predicate debug_end 0 is called if it is visible in the calling module or in the specified Module Arguments Goal Goal Exceptions instantiation_err
465. ms to the usual mathematical conventions unless the operator definitions are modified A list of arithmetic functions can be found in the description of the is 2 predicate in this manual The available functions can be divided into two classes arithmetic functions and logical functions The value of an arithmetic function results from the value of the argument s based on normal mathematical conventions The logical functions are defined only for integer arguments The corresponding bits in the Reference Manual 820 IF Prolog V5 3 Prolog text Prolog Syntax internal representation of these integers are ANDed and ORed as specified the resulting bit pattern again represents an integer which is the result of the function Many standard arithmetic functions trigonometry logarithms etc are available as Prolog functions Examples of arithmetic expressions user 5 4 1 no evaluation term unification no user N 4 N1 is N 1 N 4 Ni 65 yes user K 33 T is 2 2 K 33 9 K 33 T 106 5 yes user X is time 1000 X 709476 yes 9 5 Prolog text A Prolog text consists of clauses directives and grammar rules Clauses define predicates which can be stored in the data base and be executed All built in predicates and language constructs are described in greater detail in the alphabetic section of this manual Directives are evaluated when Prolog programs are loaded They a
466. n atom existence_error module The argument Goall or Goal2 or a subgoal is qualified by means of 2 or 2 with an atom that does not name an existing module Hints The arguments Goall and Goal2 may themselves be composite goals The atom is defined as an infix operator The language construct 2 is not a predicate so it cannot be redefined The predicates current_predicate 1 and current_visible 2 do not indicate language constructs Reference Manual 42 IF Prolog V5 3 2 Language construct Execution control Explicit module qualification with 2 or 2 is not permitted for language constructs with the exception of cal1 1 The predicates activated in the goal must be visible in the specified Module unless the 2 qualification is used for such a predicate to indicate explicitly the module in which this predicate is visible The predicates activated in the goal are normally executed in the context of the module in which they are defined This does not apply to metapredicates which are executed in the context of the specified Module unless the 2 qualification is used for a meta predicate to indicate explicitly the module context in which this predicate is to be executed Example user member X a b c member X b d a lt ENTER gt X a lt ENTER gt X b lt ENTER gt no user X is 7 lt ENTER gt X lt 10 X gt 3 lt ENTER gt X 7 lt ENTER gt yes user fail tr
467. n atom type_error integer The arity of the predicate Predicate must be an integer domain_error not_less_then_zero The arity of the predicate Predicate must be a positive integer but is negative representation_error max_arity The arity of the predicate Predicate must be an integer in the range 0 127 but is larger permission_error modify procedure The predicate indicator Predicate specifies a predicate which already exists and is not modifiable or which is the name of a language construct type_error atom The argument After must be an atom but is a term of another type domain_error on_or_off The argument After must be one of the atoms on or off but is another atom type_error atom The argument Before must be a variable or an atom but is a term of another type domain_error on_or_off The argument Before must be a variable or one of the atoms on or off but is another atom permission_error access system_module The predicate list_mode 3 must not be executed for a system module Hints The predicate list_mode 3 is a metapredicate and manipulates the database in the calling module or in the specified Module A predicate may have certain attributes which when it is created are set implicitly by the system according to the current environment or declarations They can be modified to a certain extent explicitly by the user These include the following e List mode see list_mode 3 e Debug mode see debug_mo
468. n integer representing a character code Furthermore if an arithmetic expression is specified for an element in List all the exceptions for is 2 can occur Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also socket 3 current _socket 3 select 3 host_addr 2 net_service 3 socket_accept 3 socket_bind 2 socket_connect 2 socket_close 1 socket_listen 1 2 socket_receive 2 3 socket_raw_receive 4 5 socket_shutdown 1 2 Reference Manual 524 IF Prolog V5 3 socket_shutdown 1 2 Predicate Net communication Close a socket socket_shutdown Socket socket_shutdown Socket How The predicate socket_shutdown 2 causes all or part of a full duplex connection on the socket Socket to be shut down The socket may however continue existing in the operating system especially if a partner still uses it See socket_close 1 The argument How specifies which part s of the connection is to be shut down If How is 0 then further receives will be disallowed If How is 1 then further sends will be disallowed If How is 2 then further sends and receives will be disallowed The predicate socket_shutdown 1 acts as socket_shutdown 2 with How 2 Arguments Socket Socket system defined term How Integer 0 1 or 2 Exceptions instantiation_error The argument Socket or How must not be a variable but
469. n is specified for the argument Number or one element of List all the exceptions for is 2 can occur Reference Manual 374 IF Prolog V5 3 number_codes 2 Predicate Term conversion Hints Integer expressions in List will only be evaluated if Number is not instantiated The representation of floating point numbers does not depend on the floating point format currently set but on the maximum precision Example user number_codes 1234 X lt ENTER gt X 49 50 51 52 lt ENTER gt yes Floating point numbers can also be processed user number_codes X 49 46 50 lt ENTER gt X 1 2 lt ENTER gt yes The conversion does not depend on the floating point format currently set user float_format F F lt ENTER gt number_codes 1 2 L lt ENTER gt F g 0 6 L 49 46 49 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 lt ENTER gt yes user float_format _ e 0 1 lt ENTER gt float_format F F lt ENTER gt number_codes 1 2 L lt ENTER gt F e 0 1 L 49 46 49 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 lt ENTER gt yes Standard This predicate complies with the definition of the ISO standard for Prolog IF Prolog V5 3 375 Reference Manual Term conversion Predicate number_codes 2 The use of arithmetic expressions in the arguments Number and List is not allowed in the ISO standard for Prolog In the ISO compatibility mode see Prolog flag iso therefore no arithmetic
470. n operator and a subsequent term in parentheses Otherwise Prolog will interpret the operator as the functor of a normal structure For internal processing expressions in operator notation are converted to the equivalent normal structure When terms are output with a write or writeq predicate expressions are shown in operator notation the same applies to when clauses are listed using listing 0 1 With the predicate write_term 2 3 terms can be output in normal structure notation if the option ignore_ops true is specified user write_term 3 is 2 1 Lignore_ops true is 3 2 1 yes Examples of expressions Reference Manual 810 IF Prolog V5 3 Terms Prolog Syntax Many frequently used operators are built in The following are therefore equivalent Operator notation Equivalent normal structure 2 4 5 2 4 5 25 5 3 1 Eea 3 1 ob 9 9 3 AEZ Goal Goal listing likes 2 my_module listing likes 2 my_module Once the following operators have been declared user op 200 yfx likes yes user op 180 xf is_a_god yes the following expressions are equivalent Operator notation Equivalent normal structure jones likes tiger likes jones tiger zeus is_a_god is_a_god zeus Lists A list may be either of the following empty list non empty list The empty list is represented as a pair of square brackets is not a structure but an atom wi
471. n_error The argument Name must not be a variable but a variable was specified type_error atom The argument Name must be an atom but is a term of another type existence_error global_variable The argument Name is not the name of an existing global variable Hints Global variables are always assigned to a module they can be neither exported nor imported In operations with global variables therefore only those global variables defined in the calling module or in the specified Module are taken into account Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also current_global 1 pop_global 2 push_global 2 set_global 2 unset_global 1 Reference Manual 276 IF Prolog V5 3 get_last 2 3 Predicate Screen control Determine the cursor position get_last Line Column get_last Stream Line Column The predicate get_last 2 supplies the coordinates of the cursor on the screen linked to the current output stream if the device driver for this stream is capable of supplying this information If there is no screen linked to the current output stream or if the device driver is not capable of supplying this information the position set when move_cursor 2 3 was last called is supplied The predicate get_last 3 acts in the same way as get_last 2 but uses the screen linked to the specified o
472. n_error max_arity The argument Arity must be an integer within the range 0 127 Reference Manual 326 IF Prolog V5 3 listing 0 1 Predicate Database Hints The predicate listing 0 1 is a metapredicate and considers only predicate definitions which are visible in the calling module or in the specified Module Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also list_mode 3 match 2 3 asserta_with_ names 2 3 assertz_with_names 2 3 clause_with_names 3 IF Prolog V5 3 327 Reference Manual Database Predicate load 1 Load compiled Prolog text load Filename The predicate load 1 loads the Prolog text stored in internal format from the file Filename If Filename does not contain the extension cmp and if a file of this name cannot be opened for reading the extension is appended and the resultant filename is used Such a file may have been created with compile 1 save_module 1 or the procmp command and contains either a module interface or a complete module with interface and body If there is already a module with the same name as that in Filename in the IF Prolog system it is deleted before Filename is loaded Once the module has been loaded the init 1 or initialization 1 directives specified in the body of the module are executed i e the goals specified there are executed in the con
473. n_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error output stream The argument Stream is not a stream which has been opened for output open mode write or append system_error write system_error close system_error flush_output system_error interrupted The indicated error was reported by the operating system when writing on the output stream Stream type_error atom The argument Format must be an atom but is a term of another type domain_error write_format The argument Format contains an invalid format specification IF Prolog V5 3 609 Reference Manual Formatted input output for terms Predicate write_formatted 2 3 type_error list The argument TermList must be a list but is a term of another type type_error An element of TermList must be of the specified type but is a term of another type Furthermore if an arithmetic expression is specified for an element in TermList all the exceptions for is 2 can occur Hints Since the terms in TermList are processed in the order in which they are specified partial output may occur even if Format or TermList contain errors The output produced by write_formatted 1 2
474. names Clause VarList Module assertz_with_names Head Body VarList Module The predicate assertz_with_names 2 acts in the same way as assertz 1 but the infor mation in the list VarList on variables in the clause is also stored in the database The predicate assertz_with_names 3 acts in the same way as assertz 2 but the infor mation in the list VarList on variable in the clause is also stored in the database The list VarList contains information on the variables occurring in the clause and their names in the following format Name Variable Only the information relating to the clause is transferred to the database The information in VarList need not be complete Arguments Clause Structure atom Head Structure atom Body Term VarList List with format Name Variable Name Atom Variable Variable Exceptions instantiation_error The argument Head Clause or VarList must not be a variable but a variable was specified type_error callable The argument Head Body or Clause must have the syntactical structure of a Prolog goal permission_error modify static_procedure The argument Head or the head of Clause specifies an existing predicate which has not been declared as dynamic and therefore cannot be modified permission_error access calling_context The argument Body or the body of Clause contains a call involving calling_con text 1 in a predicate that is not a metapredicat
475. nd O is not a built in predicate but one which can be defined by the user It is called in the module in which trace 1 was called It is called automatically after trace 1 has been processed The user can define trace_end O to perform terminating tasks such as closing files when the tracer is deactivated Hints This predicate is not part of the IF Prolog runtime system and is therefore not available for applications intended for third parties Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also trace 1 trace_begin 0 Reference Manual 578 IF Prolog V5 3 trace_output 4 User definable predicate Tracing User defined output predicate for the tracer trace_output CallNumber Port Goal VariableNames Body The predicate trace_output 4 is not a built in predicate but one which can be defined by the user It is called in the module in which trace 1 was called It is automatically called for the output of the trace log instead of the internal output function of the tracer This enables the user to create a separate log or to process data from the tracer directly The predicate trace_output 4 is called by the tracer with CallNumber as a list with the format RecursionDepth SubGoalNumber the name of the specified Port and the Goal to be traced If an exception has been triggered the pre
476. nded for third parties Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also debug 1 trace_config 3 system_parameters 1 Reference Manual 210 IF Prolog V5 3 debug_end 0 User definable predicate Debugger User defined termination of the debugger debug_end Body The predicate debug_end O0 is not a built in predicate but one which can be defined by the user It is called in the module in which debug 1 was called It is called automatically after debug 1 has been processed The user can define debug_end O to perform terminating tasks such as closing files when the debugger is deactivated Hints This predicate is not part of the IF Prolog runtime system and is therefore not available for applications intended for third parties Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also debug 1 debug_begin 0 IF Prolog V5 3 211 Reference Manual Database Predicate debug_mode 3 Query and set the debug mode of a predicate debug_mode Predicate Before After Module The predicate debug_mode 3 defines whether the Predicate is to be monitored by the de bugger or the tracer of IF Prolog Identification of the predicate is based on its visibility in t
477. nding floating point number to integer I truncate N Truncating floating point number to integer I Arithmetic functions with arity 1 based on C functions The C funct column indicates the C function on which the Prolog function is based IF Prolog V5 3 311 Reference Manual Arithmetic Predicate is 2 Name Function Res type C Funct abs N Absolute value I abs I abs Q abs Q R abs R fabs acos N Arc cosine R acos asin N Arc sine R asin atan N Arc tangent R atan cos N Cosine R cos cosh N Hyperbolic cosine R cosh exp N Exponential function R exp log N Natural logarithm R log sign N Sign function I sign QI R sign R signum N Sign function I signum N sin N Sine R sin sinh N Hyperbolic sine R sinh sqrt N Square root R sqrt tan N Tangent R tan tanh N Hyperbolic tangent R tanh Special arithmetic functions for floating point numbers Name float_integer_part N float_fractional_part N Function floating point number as floating point number Logical functions with arity 1 Integer part of a floating point number as Fractional part of a floating point number Res type R R Functor Function Res type Type Prec Complement PSNI fy 200 Logical functions with arity 2 Functor Function Res type Type Prec Bitwise disjunction OR I I VVI yfx 500 Bitwise conjunction AND I I I yfx 500 Bitwise exclusive or XOR I I1 I
478. ng signal_control Signal Command The predicate signal_control1 2 enables the user to control signal processing by specifying the following Commands default Activates the default signal handling mechanism of the operating system for Signal In most cases this involves aborting the process when the signal is received The predicate signal_control 2 is always successful with this Command ignore The signal handling mechanism of the operation system for Signal is de activated The predicate signal_control 2 is always successful with this Command off Activates the passive signal handling mechanism of IF Prolog for Signal This means that arrivals of the specified Signal are registered and counted but no action is taken The predicate signal_control1 2 is always successful with this Command on Activates the active signal handling mechanism of IF Prolog for Signal In other words if Signal is received or was registered earlier by passive signal handling a user defined signal handling routine is activated if defined with signal_handler 3 or context 2 or an exception of the form error system_error error interrupt signal Signal goal Goal is created If a predicate implemented in C is interrupted the entry in terrupted Predicate is added to the above mentioned list The predicate signal_control 2 is always successful with this Command clear Resets the counter for incoming signals of the type Signal to 0
479. ng module existence_error module_body The argument Module specifies a module for which no body exists permission_error access system_module The predicate set_default_module 1 must not be executed for a system module Hints When IF Prolog starts the built in module user is the current module In the input loop of IF Prolog break 0 the current module is always shown in the prompt Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also module 1 current_module 1 current_default_module 1 IF Prolog V5 3 479 Reference Manual Stream processing Predicate set_error 1 Set current error output stream set_error Stream The predicate set_error 1 makes Stream the current error output stream This stream is used by IF Prolog for the output of error messages and warnings and is accessible under the alias current_error Arguments Stream Stream system defined term or alias atom Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an
480. ninstantiated If common variables occur in Term and Goal the elements of TermList will contain each instantiation determined by a solution for these variables If Term contains variables which do not occur in Goal they are stored uninstantiated in TermList If Term and Goal do not contain common variables or if Term contains no variables then TermList will contain the term Term as many times as Goal has solutions Arguments Term Term Goal Goal TermList List Exceptions instantiation_error The argument Goal must not be a variable but a variable was specified type_error callable The argument Goal must have the syntactical structure of a Prolog goal existence_error procedure In executing Goal a predicate was to be activated which is not defined and the Prolog flag unknown has the value error type_error atom The argument Goal or a subgoal has been qualified by means of 2 or 2 with a term that is not an atom existence_error module The argument Goal or a subgoal is qualified by means of 2 or 2 with an atom that does not name an existing module type_error list The argument TermList must be a variable or a list but is a term of another type IF Prolog V5 3 249 Reference Manual Execution control Predicate findall 3 Hints The predicate findall1 3 is a metapredicate and calls its goal in the calling module or in the specified Module The predicates activated in the goal must be visible in the c
481. nput of some Words lt ENTER gt A Input lt ENTER gt A of lt ENTER gt A some lt ENTER gt IF Prolog V5 3 269 Reference Manual Elementary input output Predicate get_char 1 2 A Words lt ENTER gt yes Standard These predicates comply with the definition of the ISO standard for Prolog Compatibility V5 0B ISO conformance exception permission_error input binary_stream is gen erated instead of permission_error input text_stream when the stream is not a text stream See also peek_char 1 2 get_byte 1 2 get code 1 2 Reference Manual 270 IF Prolog V5 3 get_code 1 2 Predicate Elementary input output Input a character get_code CharCode get_code Stream CharCode The predicate get_code 1 reads the next character from the current input stream cur rent_input and unifies CharCode with its integer value The predicate get_code 2 acts in the same way for the specified input stream Stream If the end of the input stream has been reached CharCode is unified with 1 The predicates can be applied only for text streams see open 3 4 Arguments Stream Stream system defined term or alias atom CharCode Integer Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been
482. nstraint 0 cannot be executed since there are no pending constraints domain_error arity The command view_constraint 0 was called with an incorrect number of param eters Hints The information described here is formatted in accordance with the interface The appearance of the output therefore depends on the interface If the alpha interface is used the message CONSTRAINTS PENDING is displayed in the information area if constraint subgoals are pending See also view_variable 1 Reference Manual 674 IF Prolog V5 3 view_module 0 1 Debugger command Command interface Display list of predicates in module view_module vm view_module Module vm Module The view_module 0 1 commands displays the predicates of Module from the Prolog data base The predicates are displayed with the clause and subgoal numbers These numbers can be used with stop 4 and stop_interactive 1 2 4 when a breakpoint is created If this command is called without parameters the predicates from the current module are displayed Arguments Module Atom name of a module Exceptions instantiation_error The argument Module must not be a variable but a variable was specified type_error atom The argument Module must be an atom but is a term of another type existence_error module The argument Module is not the name of an existing module permission_error access system_module The predicate Module must not be exe
483. nstruct permission_error directive module The specified directive private 1 is not valid in this position Hints The atom private is defined as a prefix operator Directives are evaluated during consultation see consult 1 reconsult 1 or compi lation see compile 1 procmp command Standard The directive private 1 is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also module 1 import 1 2 meta 1 export 1 dynamic 1 Reference Manual 414 IF Prolog V5 3 profile 1 2 Predicate Profiling Activate profiling for a goal profile Goal Module profile Goal Ports Module The predicates profile 1 2 activate the profiler for executing Goal The profiler counts on a pre predicate basis how many times Prolog execution passes given ports The argument Ports specifies which ports should be counted The predicate profile 1 is equal to the predicate profile 2 with Ports set to the list call exit redo fail The profiler is based on the Prolog tracer It re defines the predicate trace_output 4 in the module user Therefore the profiler should not be used in conjunction with the tracer Arguments Goal Goal Ports List of atoms call exit fail redo suspend wakeup error failmatch enterbody exitbody redobody trymatch failbody Exceptions instantiation_error T
484. nt Stream must be a text stream but is associated with a binary stream type_error character The argument Char must be a character but is a term of another type representation_error character The argument Char is not representable as a single character system_error write system_error close system_error flush_output system_error interrupted The indicated error was reported by the operating system when writing on the output stream Stream Reference Manual 430 IF Prolog V5 3 put_char 1 2 Predicate Elementary input output Example Output of individual characters user put_char a put_char t lt ENTER gt put_char b put_char n lt ENTER gt a b yes Standard These predicates comply with the definition of the ISO standard for Prolog Compatibility V5 0B ISO conformance exception permission_error output binary_stream is generated instead of permission_error output text_stream when the stream is not a text stream See also get_char 1 2 put_byte 1 2 put_code 1 2 IF Prolog V5 3 431 Reference Manual Elementary input output Predicate put_code 1 2 Output a character put_code CharCode put_code Stream CharCode The predicate put_code 1 outputs a character which has the character code CharCode to the current output stream current_output The predicate put_code 2 has the same effect but on the specified output stream Stream
485. nt Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error output stream The argument Stream is not a stream which has been opened for output open mode write or append system_error write system_error close system_error flush_output system_error interrupted The indicated error was reported by the operating system when writing on the output stream Stream Hints The call IF Prolog V5 3 601 Reference Manual Input output for terms Predicate write 1 2 write Term is identical to write_term Term quoted false ignore_ops false numbervars true The output produced by write 1 2 is generally not suitable for re input e g with read_term 2 3 Example user write hello nl lt ENTER gt hello yes user write new nLine nl lt ENTER gt new Line yes user write Robert s daughter nl lt ENTER gt Robert s daughter yes user write 3 7 8 3 nl lt ENTER gt 3 7 8 3 yes Standard These predicates comply with the definition of the ISO standard for Prolog See also writeq 1
486. ntt display_term TermArg argno t TermCollect context NULL printt break default printt q t The following simple C function realizes a predicate write_lisp_list 1 which prints elements of a list in LISP notation using the C function display_lisp BOOLEAN write_lisp_list_1 void xx write_lisp_list Term TERM tail tail PrologArg 1 while TermIsList tail khead amp tail display_lisp head return ErrorContextIsSet void Cboot void CPRIM write_lisp_list 1 write_lisp_list_1 IF Prolog V5 3 743 Reference Manual Active C interface C Function TermCollect TermCollectSequence See also TermContext Reference Manual 744 IF Prolog V5 3 TermContext C Function Active C interface Determine current term context include cpred h TERMCONTEXT TermContext void The function TermContext determines the current term context The term context comprises all term variables managed by the C interface when Term Context is called Example See example at TermCollect See also TermCollect TermCollectSequence IF Prolog V5 3 745 Reference Manual Active C interface C Function TermDecompose Classify term include cpred h TERMTYPE TermDecompose TERM Term TERMINFO Info The function TermDecompose returns the type of the term Term In addition the Info argum
487. nual 696 IF Prolog V5 3 EndProlog C Function Passive C interface Release memory space used by IF Prolog include cpro h BOOLEAN EndProlog void The function EndProlog releases the memory space used by IF Prolog The function EndProlog always returns TRUE Hints If after calling EndProlog a further goal needs to be executed IF Prolog must be initialized again with InitProlog and the goal must be parsed with ParseProlog Calling EndProlog is not mandatory but is advisable for reasons of memory space economy See also InitProlog IF Prolog V5 3 697 Reference Manual Active C interface C Function ErrorContextClear Clear error context include cpred h void ErrorContextClear void The function ErrorContextClear clears the error context Hints The error context is always cleared before a C predicate is called If a C predicate returns FALSE and the error context is set IF Prolog automatically initiates an excep tion which refers to the C predicate and takes the information in the error context into consideration Example The following simple C function realizes a predicate is_list 1 which checks if its argument is a regular list include cpred h static BOOLEAN is_list_1 void is_list Term TERM tail tail PrologArg 1 while TermIsList tail NULL amp tail if ErrorContextIsSet Err
488. o Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also atom 1 atomic 1 compound 1 cyclic 1 float 1 ground 1 integer 1 nonvar 1 number 1 var 1 Reference Manual 434 IF Prolog V5 3 rational 3 Predicate Term conversion Decompose a rational number rational Number Numerator Denominator The predicate rational 3 determines the denominator and numerator of a rational number If Number is a rational number then Numerator is unified with the numerator and Denom inator with the denominator of this number If Number is an integer Numerator is unified with Number and Denominator with 1 Arguments Number Rational number or integer Numerator Integer Denominator Integer Exceptions instantiation_error The argument Number must not be a variable but a variable was specified type_error rational The argument Number must be a rational number or an integer but is a term of another type type_error integer The argument Numerator or Denominator must be a variable or an integer but is a term of another type Example user rational 0r3 7 Numer Denom lt ENTER gt Numer 3 Denom 7 lt ENTER gt yes user X is Or1 6 Ori 5 Ori 4 Or1 3 Or1 2 lt ENTER gt rational X Numer Denom lt ENTER gt X 0r29 20 Numer 29 Denom 20 lt ENTER gt IF Prolo
489. o letter 1 IF Prolog V5 3 335 Reference Manual System information Predicate manual 0 1 Output manual pages manual manual Functor manual Predicate The predicate manual 1 writes on current output the manual page s for the predicates with the functor Functor or the specified Predicate if such information is available The predicate succeeds even if there are no manual pages for the specified predicate The manual pages are output for all visible predicates It is therefore sometimes necessary to import the system module containing the predicate The predicate manual 0 outputs this manual page Arguments Predicate Structure with the format Functor Arity Functor Atom Arity Integer 0 lt Arity lt 127 Exceptions instantiation_error The argument Predicate Functor or Arity must not be a variable but a variable was specified type_error atom The argument Functor must be an atom but is a term of another type type_error integer The argument Arity must be an integer but is a term of another type domain_error not_less_than_zero The argument Arity must be a positive integer but is negative representation_error max_arity The argument Arity must be an integer within the range 0 127 Hints Files containing the manual pages for all installed components of the IF Prolog system are located in the IF Prolog root directory see proroot 1 Reference Manual 336 IF Prolog
490. o a 277 get_socket_option 3 Get socket option 279 get_until 3 4 Read up to a specific character 0 281 vii getchar 3 Access a character in an atom 2 24 ce eee Rae ee ew 283 getcwd 1 Query current working directory 285 getenv 2 Query environment variable 287 pround 1 Test for ground instantiation o e c a ea dee Had oe eR DS 289 bale sos i Terminate Prolog 4 244446 644 4 Rd REEEE Aw S 290 help 0 1 Display help information 020 291 host_addr 2 Query names or addresses of host 294 if 3 IF THEN ELSE nj nction of goals lt sc ae aa 8 ee eae giaws 296 import 1 2 Import predicates gt socs si sis er Bac eg Ree A eee 299 include 1 Include a Prolog file in the source text 302 index 3 Determine the position of a character string in an atom 304 init 1 initialization 1 mitidlization goal 2 44464444645 306 integer 1 Test for integer ke kk ek eee ea eee eR 308 is 2 Evaluate arithmetic expressions 22020 309 letter 1 Test for letter soci ae we ee ee ee ee ee eS 316 list_last 2 Last clement in ligt 2 nea e ne ce pede Pewee Nee ee 317 list_length 2 Count the elements ina list 319 list_mode 3 Query and set the list mode of a predicate 321 list_nth 3 Access elements of a list oaaae 324
491. o the next outer context If no matching context can be found program execution is aborted with an error message Arguments Ball Nonvar Exceptions instantiation_error The argument Ball must not be a variable but a variable was specified system_error missing_catcher The argument Ball does not match any active context of the Prolog system Hints The predicate break 0 Prolog input loop defines a context which intercepts all context jumps Reference Manual 568 IF Prolog V5 3 throw 1 Language construct Contexts Exceptions Example user listing lt ENTER gt h user foo 1 x foo X Y is X 2 throw test Y yes user catch foo 5 test Y write Y lt ENTER gt 10 Y 10 lt ENTER gt yes Standard This predicate complies with the definition of the ISO standard for Prolog Compatibility V5 0A The data structures used by the system in implicit throw 1 calls have changed and are incompatible with the previous version of IF Prolog V5 0B ISO conformance exception is generated when Ball is a variable See also abort 0 catch 3 context 2 exception 2 IF Prolog V5 3 569 Reference Manual Operating System Predicate timezone 4 Determine time and time zones timezone Time TimeZone AlternateZone DaylightSaving The predicate timezone 4 determines for a given system time see function time in is 2 the differences in seconds between U
492. oal is defined by the goal term Goal and VarList the list of the variables in Goal This can be the result of a preceding call of ParseProlog The goal will be executed in the module context Module Arguments Module Structure see PrologModule Goal Term VarList Term list of variables in Goal See also ParseProlog PrologModule QueryDispose QueryOpen Reference Manual 732 IF Prolog V5 3 Query Dispose C Function Passive C interface Release passive Prolog goal include cpro h void QueryDispose t_query Query The function QueryDispose releases a passive Prolog goal and all resources used by the goal Arguments Query Structure information on the passive Prolog goal Hints After the call of QueryDispose the data structure Query is undefined See also QueryCreate QueryOpen IF Prolog V5 3 733 Reference Manual Passive C interface C Function QueryOpen Activate a passive Prolog goal include cpro h t_cursor QueryOpen t_query Query The function QueryOpen activates a passive Prolog goal This Prolog goal also becomes the current Prolog goal The goal can then be executed with PrologFetch The function returns the structure t_cursor containing the information about the state of the active Prolog goal This information will be used as reference to the current goal A goal that was the current goal before the call of QueryOpen
493. ocess from which it was called Arguments Pid Integer Exceptions type_error integer The argument Pid must be a variable or an integer but is a term of another type Hints The predicate unix_getpid 1 is based on the C function getpid 2 see 10 This predicate is system dependent and may not be available on all operating systems Example user unix_getpid Pid lt ENTER gt Pid 3435 lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also unix_kill 2 unix_wait 1 2 unix_fork 1 IF Prolog V5 3 587 Reference Manual Operating system Predicate unix_kill 2 Send signal to a process unix_kill Pid Signal The predicate unix_kill1 2 sends the signal specified by Signal to the process specified by Pid If the signal in question cannot be sent unix_kill 2 fails If 0 is specified for Signal no signal is sent but a check is made to determine whether a signal could be sent to Pid This feature can be used to check whether a particular process exists If the process does not exist unix_kill 2 fails Some of the more important signal numbers are listed below Prolog name C name Signal number SIGHUP 1 interrupt SIGINT 2 quit SIGQUIT 3 abort SIGABRT 6 SIGKILL 9 pipe SIGPIPE 13 alarm SIGALRM 14 termination SIGTERM 15 user_1 SIGUSR1 16 user_2 SIGUSR2 17 I
494. odify procedure The predicate indicator Predicate in PredicateList specifies a predicate which al ready exists and is not modifiable or which is the name of a language construct permission_error directive module The specified directive discontiguous 1 is not valid in this position Hints The atom discontiguous is defined as a prefix operator Directives are evaluated during consultation see consult 1 reconsult 1 or compi lation see compile 1 procmp command Standard The directive discontiguous 1 complies with the definition of the ISO standard for Prolog See also consult 1 reconsult 1 compile 1 load 1 multifile 1 Reference Manual 220 IF Prolog V5 3 dynamic 1 Directive Database Declare predicates as modifiable dynamic PredicateList dynamic PredicateList Predicates declared with the directive dynamic 1 can be modified after definition even if the module to which they belong is compiled or the Prolog flag debug is set to off All predicate attributes list mode debug mode modification mode and exception mode for the predicates listed in PredicateList are set to on The directive dynamic 1 may only occur in the declaration part of a module body The first dynamic 1 directive indicating a predicate must precede all clauses for this predicate Arguments PredicateList List with the format Predicate or structure with the format Predicate Predicate Structure with the for
495. odule or in the specified Module The predicates activated in the goal must be visible in the calling module or in the specified Module unless the 2 qualification is used for such a predicate to indicate explicitly the module in which this predicate is visible The predicates activated in the goal are normally executed in the context of the module in which they are defined This does not apply to metapredicates which are executed in the context of calling module or the specified Module unless the 2 qualification is used for a metapredicate to indicate explicitly the module context in which this predicate is to be executed IF Prolog V5 3 377 Reference Manual Execution control Predicate once 1 Example user once member S 1 2 3 lt ENTER gt S 1 lt ENTER gt no Standard This predicate complies with the definition of the ISO standard for Prolog See also call 1 0 2 2 set_prolog_flag 2 Reference Manual 378 IF Prolog V5 3 op 3 Predicate Input output for terms Define and delete operators op Priority Assoc Names The predicate op 3 can be used to define operators and to delete operator definitions Operators permit terms to be entered or displayed in operator notation instead of the normal structure notation This enables predicates to be represented in a more readable format If Names is an atom the atom is defined or deleted as an operator If Names is a l
496. of a module Exceptions type_error atom The argument Module must be a variable or an atom but is a term of another type Hints A module name is still known even if its interface and its body have been deleted by unload 1 The sequence of solutions is undefined if current_module 1 has several solutions for the current call Reference Manual 184 IF Prolog V5 3 current_module 1 Predicate Module concept Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also module 1 set_default_module 2 current _default_module 1 IF Prolog V5 3 185 Reference Manual Input output for terms Predicate current _op 3 Information on operators current_op Priority Assoc Name The predicate current_op 3 supplies information on the operators defined During backtracking Name is unified with the name of the operator Assoc with the identifier for its associativity see op 3 and Priority with its operator precedence The predicate current_op 3 succeeds by backtracking for all the operators which existed at the time of the first call even if they have since been deleted or others have been added logic update view Arguments Priority Integer 1 1200 Assoc Atom xf yf fx fy xfx xfy yfx Name Atom Exceptions type_error integer The argument Priority must be a variable or an intege
497. of the system defined term Stream Any Stream may have more than one alias Arguments Alias Atom Stream Stream system defined term or alias atom Exceptions instantiation_error The argument Alias or Stream must not be a variable but a variable was specified type_error atom The argument Alias must be an atom but is a term of another type permission_error open source_sink The argument Alias specifies an alias name that is already being used domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream Hints Aliases may already be defined at open 4 Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also cancel_alias 1 current_alias 2 open 3 4 set_input 1 set_output 1 set_error 1 Reference Manual 92 IF Prolog V5 3 at_end_of_line 0 1 Predicate Elementary input output Query end of line at_end_of_line at_end_of_line Stream The predicate at_end_of_line O succeeds if the current input stream current_input is positioned at the end of a line The predicate at_end_of_line 1 succeeds if the specified inp
498. og Therefore it is not available in ISO compatibility mode see Prolog flag iso Reference Manual 538 IF Prolog V5 3 stream_device 2 Predicate Stream processing See also open 3 4 stream_property 2 stream_type 2 IF Prolog V5 3 539 Reference Manual Stream processing Predicate stream_property 2 Query information on input output streams stream_property Stream Info The predicate stream_property 2 unifies by backtracking its arguments with information on all opened input output streams Most of this information corresponds to the open 3 4 parameters The following information can be obtained and unified with Info file_name Device Name Corresponds to the first argument of open 3 4 input The Stream was opened for reading read mode with open 3 4 output The Stream was opened for writing write or append mode with open 3 4 type Type Type is unified with the type of the stream corresponding to the option type Type with open 4 buf fer Buffering Buffering is unified with the type of buffering defined for Stream with open 4 reposition Mode Mode is unified with true if repositioning of Stream is possible otherwise with false position Position If repositioning is possible for Stream Position is unified with the current position of the input output stream Position is a device specific term that can be used with set_stream_position 2 alias Alias Alias is unified with each
499. og clauses Directives occurring in Filename are evaluated and executed according to their functionality This may affect the further operation of reconsult 1 operator and module definitions for example The following directives are available Directive Description op 3 Define and delete operators char_conversion 2 Define a character conversion include 1 Include a Prolog file in the source text ensure_loaded 1 Insert a Prolog file in the source text once discontiguous 1 Declare discontiguous predicate definition multifile 1 Declare predicates as being scattered over several files init 1 Initialization goal initialization 1 Initialization goal dynamic 1 Declare predicates as modifiable module 1 Define a module begin_module 1 Define the body of a module end_module 0 1 Conclude the definition of a module import 1 2 Import predicates export 1 Export predicates of current module reexport 1 Reexport predicates of imported module Reference Manual 446 IF Prolog V5 3 reconsult 1 Predicate Database meta 1 Declare metapredicates private 1 Declare predicates as private Arguments Filename Atom name of a file or the atom user Exceptions instantiation_error The argument Filename must not be a variable but a variable was specified type_error atom The argument Filename must be an atom but is a term of another type domain_error file_name The value of the argument Filename is not a valid name for a file permission_error
500. ol is true an attempt is first made to call the user defined predicate portray 2 in the calling module or in the specified Module in order to output Term If this call succeeds write_term 2 3 will not generate its own output If the call fails the attempt is repeated for each subterm of Term and the predicate write_term 2 3 outputs those parts of Term for which the calls to portray 2 fail If Bool is false default no attempt to call a user defined predicate is made numbervars Bool If Bool is true and Term contains subterms in the form gt VAR N these subterms are replaced by symbolic variable names by constructing names in relation to the value of N The numbers 0 25 are mapped to the names A Z the numbers 26 51 to the names A1 Z1 and so on varnames VarList If Term contains a variable VarList is checked to see if it contains an element of the form Name Variable for precisely that variable If it does the variable in question is not be represented by its internal name but by the atom Name from VarList Arguments Stream Stream system defined term or alias atom Term Term Options List of structures N Integer gt 0 Atom1 Atom2 Atom Bool Atom true false Var List List of the form Name Variable Name Atom Variable Variable Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an
501. om but is a term of another type Hints Global variables are always assigned to a module they can be neither exported nor imported In operations with global variables therefore only those global variables defined in the calling module or in the specified Module are taken into account Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also current_global 1 get_global 2 pop_global 2 push_global 2 unset_global 1 Reference Manual 482 IF Prolog V5 3 set_input 1 Predicate Stream processing Set current input stream set_input Stream The predicate set_input 1 makes Stream the current input stream This stream is used by all input predicates which are specified without an explicit stream argument and is accessible under the alias current_input Arguments Stream Stream system defined term or alias atom Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error input stream The argument Stream is not a stre
502. om the specified module permission_error directive module The specified directive import 1 2 is not valid in this position Hints The atom import is defined as a prefix operator and the atom from is defined as a infix operator Directives are evaluated during consultation see consult 1 reconsult 1 or compi lation see compile 1 procmp command Standard The directive import 1 2 is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Reference Manual 300 IF Prolog V5 3 import 1 2 Directive Module concept See also module 1 begin module 1 end_module 0 1 export 1 reexport 1 2 IF Prolog V5 3 301 Reference Manual Database Directive include 1 Include a Prolog file in the source text include Filename include Filename The effect of the directive include 1 can be interpreted as the textual replacement of the directive with the Prolog text in the file Filename Arguments Filename Atom name of a file Exceptions Errors in directives are detected with consult 1 reconsult 1 or compile 1 No exceptions are generated Instead only error messages are output on the current error output stream This directive can produce the following error messages instantiation_error The argument Filename must not be a variable but a variable was specified type_error atom The argument Filename must be an atom bu
503. on is made between two cases 1 Number is instantiated List must be either a variable or a list of variables or character codes The predicate number_codes 2 creates the list of character codes in Number and unifies the result with List If Number is an arithmetic expression the expression is evaluated first and the result is then converted into character codes 2 Number is uninstantiated List must be a completely instantiated list of character codes The predicate number _ codes 2 creates a number from List whose external representation matches the se quence of character codes in List The result is unified with Number Arguments Number Number or arithmetic expression List List of integers or integer expressions Exceptions type_error number The argument Number must be a number or an arithmetic expression but is a term of another type instantiation_error The argument List or a subterm must not be a variable but a variable was specified type_error list The argument List must be a list but is a term of another type type_error integer An element of List must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer representation_error character_code An element of List must be an integer representing a character code syntax_error illegal number The characters in List do not represent a number Furthermore if an arithmetic expressio
504. on path of IF Prolog in the current operating system The installation path will usually vary from system to system The installation path can be made known to IF Prolog explicitly using the system parameter root or the environment variable PROROOT Arguments Path Atom Exceptions type_error atom The argument Path must be a variable or an atom but is a term of another type Example user proroot Root lt ENTER gt Root usr2 ifprolog system lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also system_name 1 prolog_version 1 Reference Manual 426 IF Prolog V5 3 push_global 2 Predicate Global variables Set value of a global variable push_global Name Value Module The predicate push_global 2 pushes Value onto the value stack of the global variable Name in the calling module or in the specified Module thus making Value the new topmost element of the stack If the global variable Name does not exist it is created Arguments Name Atom Value Term Exceptions instantiation_error The argument Name must not be a variable but a variable was specified type_error atom The argument Name must be an atom but is a term of another type Hints Global variables are always assigned to a module they can be neither exported nor imported In o
505. onstruct permission_error directive module The specified directive dynamic 1 is not valid in this position Hints The atom dynamic is defined as a prefix operator Directives are evaluated during consultation see consult 1 reconsult 1 or compi lation see compile 1 procmp command Standard The directive dynamic 1 complies with the definition of the ISO standard for Prolog See also compile 1 load 1 predicatesmode 3 modify_mode 3 Reference Manual 222 IF Prolog V5 3 edit 0 1 Predicate Operating system Edit a file edit Module edit Filename Module The predicate edit 1 calls an editor for the specified file Filename If Filename does not contain the extension pro and if a file of this name cannot be opened for reading the extension is appended and the resultant filename is used The predicate edit 0 acts in the same way as edit 1 but edits the file last edited with edit 1 without its name having to be specified again The predicate edit 0 fails if edit 1 has not been called since IF Prolog started At the end of the editing operation you are asked Should the file Filename be reconsulted y n If you answer y or Y without blanks or other characters the file Filename is automatically reconsulted reconsult 1 in the calling module or in the specified Module If any other input is made the file will not be reconsulted In either case edit 0 1 succeeds If
506. ool true false alias Alias Repositioning shall be possible Repositioning need not be possible Assigns the specified Alias to the stream after it is opened see assign_alias 2 eof_action Action Defines how IF Prolog will respond if an attempt is made to execute further read operations after the end of the input stream is reached This entry is only possible for input streams and does not take effect until the end of the stream has been normally reached at least once The following values are possible for Action error eof_code reset Generates an exception if additional read operations are performed after the end of the input stream is reached default except for ter minals All reading predicates behave as if the end of the input stream was reached for the first time and return the indicator intended for that purpose e g end_of_file with get_char 1 2 or 1 with get_ code 1 2 If an attempt is made to read a stream again after the end of the input stream has been reached the stream is reset i e returned to the state before the end of stream was reached for the first time and the read operation is repeated The actual effect of resetting an input stream in specific cases is defined by the respective device driver This entry should therefore only be used if the corresponding effect is known and also makes sense default behavior for terminals The predicate open 3 is identical to open 4 with defaul
507. open 4 All output predicates which do not have an explicit stream argument refer to the current output stream This stream can always be addressed via the built in alias current_ output as well Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also tell 1 told 0 set_output 1 current_output 1 error_telling 1 seeing 1 IF Prolog V5 3 567 Reference Manual Contexts Exceptions Language construct throw 1 Initiate a context jump throw Ball The language construct throw 1 is a special predicate that neither succeeds nor fails Its effect is purely procedural and causes normal execution to be interrupted Calling throw 1 results in an attempt to search for the innermost context that can intercept context jumps Such a context may have been created with context Goal catch CatchMask gt SubstituteGoal or catch Goal CatchMask SubstituteGoal If the CatchMask defined here can be successfully unified with a copy of Ball execution returns to the point at which the call was made and the call to catch 3 or context 2 is replaced by the call to SubstituteGoal The result of SubstituteGoal then becomes the result of catch 3 or context 2 Backtracking by SubstituteGoal is possible If the unification of CatchMask with a copy of Ball is not successful the procedure described above is applied t
508. open input output stream permission_error output stream The argument Stream is not a stream which has been opened for output open mode write or append Example user X is 4 0 lt ENTER gt xxx EXCEPT ION evaluation_error zero_divisor no user open null null write BlackHole lt ENTER gt set_error BlackHole BlackHole gt stream 5 lt ENTER gt yes user X is 4 0 lt ENTER gt Reference Manual 480 IF Prolog V5 3 set_error 1 Predicate Stream processing no Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also set_input 1 set_output 1 current_input 1 current_output 1 current_error 1 IF Prolog V5 3 481 Reference Manual Global variables Predicate set_global 2 Set value of a global variable set_global Name Value Module The predicate set_global 2 sets the global variable Name in the calling module or in the specified Module to the given Value If the global variable Name does not exist it is created If the global variable Name has a value stack all previous values are removed from the stack thus making Value the only value in the stack Arguments Name Atom Value Term Exceptions instantiation_error The argument Name must not be a variable but a variable was specified type_error atom The argument Name must be an at
509. open source_sink The argument Filename specifies a file or a different I O medium that cannot be opened system_error read system_error interrupted The error indicated was reported by the operating system when reading the input stream Filename permission_error modify static_procedure When loading the file Filename a predicate is to be defined which already exists and which may not be modified In addition all the error messages and warnings from read_term 2 assertz 1 and assertz_with_names 2 and may occur These do not cause the load process to be aborted You should be aware that the database may not necessarily contain what you expect it to contain Errors in directives are also output as error messages on the error output stream Un known directives are reported by the error message domain_error directive In the event of errors in a module interface the affected module is deleted after Filename has been processed If there are errors in the declaration part of a module body the affected module body is deleted after Filename has been processed When initialization directives are executed see init 1 any exception may arise These aborts the execution of the initialization goal but does not abort the load process In addition warnings are output as a function of the Prolog flag warnings in certain situations to alert you to possible sources of errors IF Prolog V5 3 447 Reference Manual Database Predicate
510. or Directives are evaluated during consultation see consult 1 reconsult 1 or compi lation see compile 1 procmp command IF Prolog V5 3 227 Reference Manual Database Directive ensure_loaded 1 If Filename is not an absolute pathname the search for the file takes place relative to the directory of the file containing the ensure_loaded 1 directive If Filename does not contain the extension pro and if a file of this name cannot be opened for reading the extension is appended and the resultant filename is used Standard The directive ensure_loaded 1 complies with the definition of the ISO standard for Prolog See also include 1 Reference Manual 228 IF Prolog V5 3 error_tell 1 Predicate Stream processing Set current error output stream error_tell Stream The predicate error_tell 1 makes Stream the current error output stream If the argument Stream is not an input output stream and not a defined alias it must be an atom A file of this name is then opened for writing If this succeeds the name is simultaneously registered as an alias for the opened output stream and the stream becomes the current error output stream Arguments Stream Stream system defined term alias atom or filename atom Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream
511. or The argument Goal must not be a variable but a variable was specified type_error callable The argument Goal must have the syntactical structure of a Prolog goal existence_error procedure In executing Goal a predicate was to be activated which is not defined and the Prolog flag unknown has the value error type_error atom The argument Goal or a subgoal has been qualified by means of 2 or 2 with a term that is not an atom existence_error module The argument Goal or a subgoal is qualified by means of 2 or 2 with an atom that does not name an existing module Hints If debug 1 is called within trace 1 or debug 1 this call is ignored The predicate debug 1 is a metapredicate and calls its goal in the calling module or in the specified Module The predicates activated in the goal must be visible in the calling module or in the specified Module unless the 2 qualification is used for such a predicate to indicate explicitly the module in which this predicate is visible The predicates activated in the goal are normally executed in the context of the module in which they are defined This does not apply to metapredicates which are executed in IF Prolog V5 3 205 Reference Manual Debugger Predicate debug 1 the context of calling module or the specified Module unless the 2 qualification is used for a metapredicate to indicate explicitly the module context in which this predicate is to be executed This p
512. or integer The argument Position must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error output stream The argument Stream is not a stream which has been opened for output open mode write or append system_error write system_error close system_error flush_output system_error interrupted The indicated error was reported by the operating system when writing on the output stream Stream Furthermore if an arithmetic expression is specified for the argument Position all the exceptions for is 2 can occur IF Prolog V5 3 389 Reference Manual Elementary input output Predicate outtab 1 2 Hints If the output is sent to a terminal and inputs are made at the same time the results may be unexpected since IF Prolog cannot take inputs into account when calculating the position in an output stream The predicate outtab 1 2 positions the cursor absolutely tab 1 2 positions it relative to its current position Example Tabulated output of visible predicates user nl current_visible
513. or atom off ReadyReadStreams List of streams ReadyWriteStreams List of streams ReadyReadSOS List of sockets or streams ReadyWriteSOS List of sockets or streams TimeLeft Variable positive integer or zero IF Prolog V5 3 475 Reference Manual Net communication Predicate select 3 4 5 Exceptions instantiation_error The argument Streams resp SocksOrStreams or an element thereof must not be a variable but a variable was specified type_error list The argument Streams resp SocksOrStreams must be a list but is a term of another type domain_error stream_or_alias The argument Streams must be a list and each element of it must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream instantiation_error The argument Timeout must not be a variable but a variable was specified type_error float The argument Timeout must be a number which can be converted implicitly into a floating point number but is a term of another type domain_error not_less_than_zero The argument Timeout must be a positive number but is negative type_error variable The argument ReadyReadStreams or Ready WriteStreams must be a variable but is a term of another type type_error variable The argument ReadyReadSOS or ReadyWriteSOS must be a variable but is a term of another type type_error variable The argument Timeleft must
514. or the result of the evaluation of the expression is not an integer Furthermore if an arithmetic expression is specified for the argument Seconds all the exceptions for is 2 can occur Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1A The predicate alarm 1 is new See also signal_handler 3 signal_control 2 context 2 Reference Manual 76 IF Prolog V5 3 append 3 Predicate List processing Append or decompose lists append Head Tail List The predicate append 3 is used to append a term Tail which is normally a list to a list Head to form a complete list List There are four possible cases 1 Head and Tail are instantiated the predicate append 3 appends Tail to Head The result is unified with List 2 List and one further argument are instantiated the predicate append 3 disengages Head or Tail from List and instantiates the result to the free argument 3 Only List is instantiated during backtracking the predicate append 3 generates all possible combinations of decomposing List into Head and Tail 4 No argument or only Head or only Tail is instantiated the predicate append 3 generates variable masks see last example Arguments Head List Tail List List List Hints Head must be a regular list see section 9 If Head is a structure similar to a list see
515. or the result of the evaluation of the expression is not an integer domain_error not_less_than_zero The argument Number must be a positive integer but is negative domain_error arity The command view_ancestor 0 1 was called with an incorrect number of param eters Furthermore if an arithmetic expression is specified for the argument Number all the exceptions for is 2 can occur Hints The information described here is formatted in accordance with the interface The appearance of the output therefore depends on the interface Reference Manual 672 IF Prolog V5 3 view_configuration 0 Debugger command Command interface Display default values view_configuration VCO The view_configuration 0 command displays the current settings ports etc Exceptions domain_error arity The command view_configuration O was called with an incorrect number of parameters Hints The information described here is formatted in accordance with the interface The appearance of the output therefore depends on the interface IF Prolog V5 3 673 Reference Manual Command interface Debugger command view_constraints 0 Display constraints view_constraints vc The view_constraints 0 commands displays a pending constraint subgoal in the context of its definition The command is only permitted if a constraint subgoal is pending Exceptions existence_error pending_constraints The command view_co
516. or this predicate Arguments PredicateList List with the format Predicate or the structure with the format Predicate Predicate Structure with the format Functor Arity Functor Atom Arity Integer 0 lt Arity lt 127 Exceptions Errors in directives are detected with consult 1 reconsult 1 or compile 1 No exceptions are generated Instead only error messages are output on the current error output stream This directive can produce the following error messages instantiation_error The argument PredicateList or a subterm must not be a variable but a variable was specified type_error list The argument PredicateList must be a regular list but is a term of another type or not regular type_error predicate_indicator The argument Predicate in PredicateList must be a predicate indicator i e a structure with the format Functor Arity but is a term of another type type_error atom The name of the predicate Predicate in PredicateList must be an atom type_error integer The arity of the predicate Predicate in PredicateList must be an integer domain_error not_less_then_zero The arity of the predicate Predicate in PredicateList must be a positive integer but is negative IF Prolog V5 3 219 Reference Manual Database Directive discontiguous 1 representation_error max_arity The arity of the predicate Predicate in PredicateList must be an integer in the range 0 127 but is larger permission_error m
517. orContextClear return FALSE return TRUE void Cboot void CPRIM is_list 1 is_list_1 Reference Manual 698 IF Prolog V5 3 ErrorContextClear C Function Active C interface See also ErrorContextGet ErrorContextIsSet ErrorContextSet IF Prolog V5 3 699 Reference Manual Active C interface C Function ErrorContextGet Query error context include cpred h BOOLEAN ErrorContextGet ERRORCLASS Errorclass STRING Parml STRING Parml ARITY Argno TERM Culprit The function ErrorContextGet queries the error context If the error context is set the appropriate error context parameters see ErrorContextSet are returned and the function returns TRUE If the error context is not set the function returns FALSE In this case Errorclass Parm1 Parm2 Argno and Culprit are not changed For Errorclass Parm1 Parm2 Argno and Culprit the constant NULL can be passed instead of a pointer to the corresponding data structure In this case the corresponding argument is not set Arguments Errorclass Pointer to an element from the set ERRORCLASS see cpred h Parm1 Parm2 Pointer to character string or NULL Argno Pointer to integer or NULL Culprit Pointer to term variable or NULL Hints The error context is always cleared before a C predicate is called If a C predicate returns FALSE and the error context is set IF Prolog automatically initiates an excep tion wh
518. orm A number in square brackets indicates a reference to another man ual or a textbook The number identifies the publication in the Bibliography at the end of the manual The following pictograms are also used i for important advice and related information for warnings IF Prolog V5 3 3 Reference Manual Commands Reference section Reference Manual 4 IF Prolog V5 3 Chapter 2 Reference section on commands This section contains descriptions of the commands in alphabetical order Prolog configuration System command link_prolog Reconfigure Prolog link_prolog name The command link_prolog creates a new Prolog system kernel from the Prolog base system and additional Prolog packages Inclusion of these packages is optional and can be controlled by the user If the argument name is given on the command line the new Prolog kernel is stored in file name otherwise the new Prolog kernel is stored under the name prostd If name does not represent a path name the new Prolog kernel is stored in the bin subdirectory of the Prolog system The following steps are required to link a new Prolog kernel e The command link_prolog name is called This command can be found in the direc tory PROROOT c of the Prolog system e g opt lib prolog on some UNIX systems e For each package supported by the Prolog system Informix Motif Constraints that has been installed the system will ask i
519. orm lexical elements and delimiters Prolog character set The Prolog character set consists of the following classes of characters Letters digits underscore character Special characters Prolog specific characters e Delimiters These classes comprise the following individual characters Letters digits underscore character Prolog Syntax Basic Prolog elements Special characters Delimiters Blank Tab character New line character Prolog specific characters The Prolog specific characters have a special meaning in the Prolog syntax Character Meaning Separates arguments in structures elements in lists and conjuncted subgoals Cut Part of term and clause syntax Parentheses must always occur in pairs If one of the two parentheses is missing Prolog will report a syntax violation Part of term syntax list notation Square brackets must always occur in pairs If one of the two square brackets is missing Prolog will report a syntax violation Enclose subconditions in grammar rules Braces must always occur in pairs If one of the two braces is missing Prolog will report a syntax violation A string of characters enclosed in double quotes is interpreted according to the value of the Prolog flag double_quotes Double quotes must always occur in pairs A string of characters enclosed in single quotes is interpreted a
520. otherwise it fails Arguments Dir Atom Exceptions instantiation_error The argument Dir must not be a variable but a variable was specified type_error atom The argument Dir must be an atom but is a term of another type Example user chdir usr bin lt ENTER gt system pwd lt ENTER gt usr bin yes user chdir lt ENTER gt getcwd Pwd lt ENTER gt X usr lt ENTER gt yes user chdir hello lt ENTER gt no Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Reference Manual 138 IF Prolog V5 3 chdir 1 Predicate Operating system See also getcwd 1 windows_chdrive 1 windows_getdrive 1 IF Prolog V5 3 139 Reference Manual Database Predicate clause 2 Search the database for specific clauses clause Head Body Module The predicate clause 2 searches the database in the calling module or in the specified Module for clauses with a head which can be unified with Head If such a clause is found unification of Head is performed i e any variables in Head are unified with the corresponding arguments from the head of the clause found and Body is unified with the body of the clause found The predicate clause 2 succeeds by backtracking for all matching clauses which were found in the database at the time of the first call
521. p of is 2 if necessary Compatibility V5 0B ISO conformance exception permission_error output text_stream is gen erated instead of permission_error output binary stream when the stream is not a binary stream See also get_byte 1 1 put_char 1 2 put_code 1 2 IF Prolog V5 3 429 Reference Manual Elementary input output Predicate put_char 1 2 Output a character put_char Char put_char Stream Char The predicate put_char 1 outputs a character Char to the current output stream cur rent_output The predicate put_char 2 has the same effect but on the specified output stream Stream The predicates can be applied only for text streams see open 3 4 Arguments Stream Stream system defined term or alias atom Char Atom character Exceptions instantiation_error The argument Stream or Char must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error output stream The argument Stream is not a stream which has been opened for output open mode write or append permission_error output binary_stream The current output stream or the argume
522. pe_error list The argument List must be a list but is a term of another type type_error atom An element of List must be an atom but is a term of another type domain_error Description The argument RegExp is not a legal regular expression Description is a closer description of the error Hints This predicate is supplied as an alternative for match 2 3 to be used with more complex regular expressions It works only for atoms made up of ASCII characters Example user regexp 0 9 CLO 9 WA AA CLO 9 N 1 12 1987 K K 1 12 1987 lt ENTER gt yes user regexp 0O 9 f2 atb12c123 K K 12 lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also match 2 3 match_atom 2 IF Prolog V5 3 453 Reference Manual List processing Predicate remove 3 Remove a sublist from a list remove Sublist List Remainder The predicate remove 3 removes from List the first sublist whose elements can be unified sequentially with the elements of Sublist The list with the remaining elements is unified with Remainder Arguments Sublist List List List Remainder List Exceptions instantiation_error The argument Sublist or List must not be a variable but a variable was specified type_error
523. pe_error callable The argument Goal must have the syntactical structure of a Prolog goal existence_error procedure In executing Goal a predicate was to be activated which is not defined and the Prolog flag unknown has the value error type_error atom The argument Goal or a subgoal has been qualified by means of 2 or 2 with a term that is not an atom existence_error module The argument Goal or a subgoal is qualified by means of 2 or 2 with an atom that does not name an existing module Reference Manual 118 IF Prolog V5 3 bagof 3 Predicate Execution control type_error list The argument TermList must be a variable or a list but is a term of another type Hints The atom is defined as an infix operator The predicate bagof 3 is a metapredicate and calls its goal in the calling module or in the specified Module The predicates activated in the goal must be visible in the calling module or in the specified Module unless the 2 qualification is used for such a predicate to indicate explicitly the module in which this predicate is visible The predicates activated in the goal are normally executed in the context of the module in which they are defined This does not apply to metapredicates which are executed in the context of calling module or the specified Module unless the 2 qualification is used for a metapredicate to indicate explicitly the module context in which this predicate is to be execute
524. pen mode read Both Stream1 and Stream2 must have been opened using the same mode permission_error output stream The argument Stream2 is not a stream which has been opened for output open IF Prolog V5 3 535 Reference Manual Stream processing Predicate stream_copy 2 mode write or append Both Stream1 and Stream2 must have been opened using the same mode Hints This predicate is system dependent and may not be available on all operating systems The predicate stream_copy 2 is based on the control commands for I O streams fileno and dup The standard device drivers standard file and pipe use the C function dup 2 for this purpose see 10 Example The file example contains the following lines append A B a b c d read A 1 943 ab write test nl If this file is defined as standard input after starting IF Prolog the goals from example will be subsequently processed as if they were entered at the terminal When the end of the file is encountered IF Prolog is exited user yes yes A yes open example read S lt ENTER gt stream_copy S user_input lt ENTER gt stream 5 i a b c d 1 943 k k Syntax_error operator expected gt gt gt line 6 column 3 test yes Reference Manual 536 IF Prolog V5 3 stream_copy 2 Predicate Stream processing Standard This predicate is not required by the ISO standard for Prolog Therefore it
525. pen source_sink The argument File specifies a file or a different I O medium that cannot be opened system_error write system_error close system_error flush_output system_error interrupted The indicated error was reported by the operating system when writing on the output stream File Reference Manual 658 IF Prolog V5 3 snapshot 0 1 2 Alpha interface Alpha interface existence_error snapshot_file The command snapshot 0 was used although no snapshot file exists yet domain_error arity The command snapshot 0 1 2 was called with an incorrect number of parameters Hints These commands are only available in the alpha interface of the debugger IF Prolog V5 3 659 Reference Manual Command interface Debugger command step 0 Execute up to next monitored port step p The step 0 command is resumes the debugger session the debugger continues to the next breakpoint and switches to interactive mode if necessary All implicit breakpoints are then activated This command can also be used to trace processing step by step i e from port to port for which on has been set If this command is used in the action list of a breakpoint it must be written as step The interpretation of gt as the abbreviation of step depends on the interface Exceptions domain_error arity The command step 0 was called with an incorrect number of parameters Hints For the stream
526. pened for input open mode read system_error read Sus plete Oa a oe The error indicated was reported by the operating system when reading the input stream Stream existence_error stream The argument Stream must be associated with an open input output stream Hints The predicates at_end_of_stream 0 1 must perform a read operation in the input stream to determine whether the end of the stream has been reached It is therefore possible that the system will have to wait for an input IF Prolog V5 3 95 Reference Manual Elementary input output Predicate at_end_of_stream 0 1 Example The following predicate skips the rest of an input stream user listing lt ENTER gt h user skip_rest 1 skip_rest Stream repeat get_char Stream _ at_end_of_stream Stream yes user read user_input T lt ENTER gt skip_rest user_input lt ENTER gt read user_input N lt ENTER gt one_before_last_line Comment lt ENTER gt last_line Comment lt ENTER gt lt EQF gt T one_before_last_line N end_of_file lt ENTER gt yes Standard These predicates comply with the definition of the ISO standard for Prolog See also at_end_of_line 0 1 Reference Manual 96 IF Prolog V5 3 atom 1 Predicate Term classification Test for atom atom TestTerm The predicate atom 1 succeeds if TestTerm is an atom otherwise it fails Arguments Test Term Term Example user
527. perations with global variables therefore only those global variables defined in the calling module or in the specified Module are taken into account Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also current_global 1 get_global 2 pop_global 2 set_global 2 unset_global 1 IF Prolog V5 3 427 Reference Manual Elementary input output Predicate put_byte 1 2 Output a byte put_byte ByteCode put_byte Stream ByteCode The predicate put_byte 1 outputs the byte ByteCode to the current output stream cur rent_output The predicate put_byte 2 has the same effect but on the specified output stream Stream The predicates can be applied only for binary streams see open 3 4 Arguments Stream Stream system defined term or alias atom ByteCode Integer or integer expression 0 lt ByteCode lt 255 Exceptions instantiation_error The argument Stream or ByteCode must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error output stream The ar
528. ply a strictly conforming mode where the Prolog system only accepts and supplies conforming language predciates To invoke this mode see the section on invoking IF Prolog in the User s Guide The IF Prolog Reference Manual documents the language features of Prolog Target group The IF Prolog Reference Manual is intended for anyone working with Prolog and writing Prolog programs The manual is not designed as a textbook for the Prolog language You should therefore already have a basic knowledge of Prolog Suitable textbooks 12 13 14 are given in the Bibliography You can develop a feel for Prolog by working through the sample session described in the opening section of the IF Prolog User s Guide 2 You can do this without any previous knowledge of the language The documentation for IF Prolog comprises of the following manuals e IF Prolog Reference Manual e IF Prolog User s Guide e IF Prolog Windows Interfaces Preface e IF Prolog OSF Motif Interface e IF Prolog Constraints Package e IF Prolog Java Interface The JF Prolog Reference Manual contains a description of the semantics built in predicates C interface functions debugger commands and environment control of IF Prolog It also contains an overview of the syntax of the Prolog language Predicates associated with an interface or package are described in the respective manuals The IF Prolog User s Guide describes how to work with Prolog on
529. predicates as modifiable module 1 Define a module begin_module 1 Define the body of a module end_module 0 1 Conclude the definition of a module IF Prolog V5 3 163 Reference Manual Database Predicate consult 1 import 1 2 Import predicates export 1 Export predicates of current module reexport 1 Reexport predicates of imported module meta 1 Declare metapredicates private 1 Declare predicates as private Arguments Filename Atom name of a file or the atom user Exceptions instantiation_error The argument Filename must not be a variable but a variable was specified type_error atom The argument Filename must be an atom but is a term of another type domain_error file_name The value of the argument Filename is not a valid name for a file permission_error open source_sink The argument Filename specifies a file or a different I O medium that cannot be opened system_error read Pe ae no upted The error indicated was reported by the operating system when reading the input stream Filename permission_error modify static_procedure When loading the file Filename a predicate is to be defined which already exists and which may not be modified In addition all the error messages and warnings from read_term 2 assertz 1 and assertz_with_names 2 and may occur These do not cause the load process to be aborted You should be aware that the database may not necessarily contain what you expect it to contain Errors in di
530. predicates comply with the definition of the ISO standard for Prolog Compatibility V5 0B ISO conformance exception permission_error input binary_stream is gen erated instead of permission_error input text_stream when the stream is not a text stream See also peek_code 1 2 get_byte 1 2 get_char 1 2 Reference Manual 272 IF Prolog V5 3 get _file_info 2 3 Predicate Operating system Get operating system information on files get_file_info Pathname Info get_file_info Pathname Attribute Value The predicates get_file_info 2 3 retrieve information on files from the operating system Thus the kind and amount of information depends on the current operating system get_ file_info 2 yields all the information available in a list of the form Attribute Value whereas get_file_info 3 allows you to access information more specifically The predicate fails when you ask for an attribute that is not available for the current operating system or file system Attribute Description dev ID of device containing file ino file serial number mode mode of file see below nlink number of links to file uid user ID of file uname user name for user ID or none if not available gid group ID of file gname group name for group ID or none if not available rdev device ID for character or block special files size file size in bytes for regular files atime time of last access mtime time
531. prescribed range of values type_error integer The argument Value must be an integer but is a term of another type type_error atom The argument Value must be an atom but is a term of another type domain_error on_or_off The argument Value must be one of the atoms on or off but is another atom Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also current_socket 3 get_socket_option 3 net _service 3 select 3 socket 3 socket_accept 3 socket_bind 2 socket_connect 2 socket_close 1 socket_listen 1 2 socket_receive 2 3 socket_raw_receive 4 5 socket_send 2 3 socket_shutdown 1 2 Reference Manual 496 IF Prolog V5 3 set_stream_position 2 Predicate Stream processing Position within an input output stream set_stream_position Stream Position The predicate set_stream_position 2 sets the current position of the specified I O stream Stream to the given Position provided the device driver associated with Stream allows such positioning Positioning is possible only if the stream was opened with the option reposition see open 3 4 The Position is specified as a device specific term and should hence only be a value that was previously determined with stream_property 2 Arguments Stream Stream system defined term or alias atom Position Term device specific Exceptions instantia
532. pression RestLength gt 0 SubAtom Atom Exceptions instantiation_error The argument Atom must not be a variable but a variable was specified type_error atom The argument Atom must be an atom but is a term of another type type_error atom The argument SubAtom must be a variable or an atom but is a term of another type type_error integer The argument StartLength Length or RestLength must be a variable an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer domain_error not_less_than_zero The argument StartLength Length or RestLength must be a positive integer but is negative Furthermore if an arithmetic expression is specified for the argument StartLength Length or RestLength all the exceptions for is 2 can occur IF Prolog V5 3 545 Reference Manual String processing Predicate sub_atom 5 Example To obtain a substring user sub_atom substring 5 7 _ Z lt ENTER gt no To split a string into substrings of length 3 user sub_atom abcde P 3 _ Z lt ENTER gt P 0 Z abc lt ENTER gt P 1 Z bcd lt ENTER gt P 2 Z cde lt ENTER gt no To obtain all substrings as of position 3 user sub_atom abcde 3 _ _ Z lt ENTER gt Z lt ENTER gt Z d lt ENTER gt Z de lt ENTER gt no To split an atom fully into all possible substrings user sub_atom ab _ _ _ Z
533. ps at the goal of the back_subgoal 0 command Because execution of this command is equivalent to resetting the system to a previous state variable instantiations may be undone If no ancestor goal exists the debugger reports an error Exceptions existence_error previous_subgoal The command back_subgoal 0 cannot be executed at this point in the proof tree domain_error arity The command back_subgoal 0 was called with an incorrect number of parameters See also back_parent 0 back_clause 0 Reference Manual 636 IF Prolog V5 3 break 0 Debugger command Command interface Start new input loop break B The break 0 command starts a new input loop The debugger is interrupted for the duration of the input loop Exceptions domain_error arity The command break 0 was called with an incorrect number of parameters See also abort 0 call 1 IF Prolog V5 3 637 Reference Manual Command interface Debugger command call 1 Execute a Prolog goal call Goal Module ca Goal Module The call1 1 command is used to call the goal Goal The failure or success of this operation has no effect on the remainder of the debugger session If a module argument is specified Goal is called in the context of this module Arguments Goal Goal Exceptions instantiation_error The argument Goal must not be a variable but a variable was specified type_error callable The argument
534. pt for optimization identical to TermUnify Term TermMakeInteger Wert See also TermUnify TermMakeInteger IF Prolog V5 3 787 Reference Manual Active C interface C Function Term UnifyList Unify term with list include cpred h BOOLEAN TermUnifyList TERM Term TERM Head TERM Tail The function TermUnifyList unifies the term Term with a list whose list head is Head and whose tail is Tail If Head or Tail is NULL a new Prolog variable is used instead If unification is successful the function returns TRUE otherwise it returns FALSE Arguments Term Term variable Head Tail Term variable or NULL Hints The call of TermUnifyList Term Head Tail is except for optimization identical to TermUnify Term TermMakeList Head Tail See also Term Unify TermMakeList Reference Manual 788 IF Prolog V5 3 TermUnifyNil C Function Active C interface Unify term with the empty list include cpred h BOOLEAN TermUnifyNil TERM Term The function TermUnifyNil unifies the term Term with the empty list If unification is successful the function returns TRUE otherwise it returns FALSE Arguments Term Term variable Hints The call of TermUnifyNil Term is except for optimization identical to TermUnify Term TermMakeNil See also TermUnify TermMakeNil IF Prolog V5 3 789 Reference Manual Active C interface
535. ption 2 Arguments Goal Goal CatchMask Term SubstituteGoal Goal Exceptions instantiation_error The argument Goal or SubstituteGoal or a subterm must not be a variable but a variable was specified instantiation_error The argument Goal or SubstituteGoal must not be a variable but a variable was specified type_error callable The argument Goal or SubstituteGoal must have the syntactical structure of a Prolog goal existence_error procedure In executing Goal or SubstituteGoal a predicate was to be activated which is not defined and the Prolog flag unknown has the value error IF Prolog V5 3 131 Reference Manual Contexts Exceptions Predicate catch 3 type_error atom The argument Goal or SubstituteGoal or a subgoal has been qualified by means of 2 or 2 with a term that is not an atom existence_error module The argument Goal or SubstituteGoal or a subgoal is qualified by means of 2 or 2 with an atom that does not name an existing module Hints The predicate catch 3 is based on context 2 The predicate catch 3 is a metapredicate and calls its goal in the calling module or in the specified Module The predicates activated in the goal must be visible in the calling module or in the specified Module unless the 2 qualification is used for such a predicate to indicate explicitly the module in which this predicate is visible The predicates activated in the goal are normally executed in the context of t
536. query drive 600 environment variable query 287 epilog enable 719 error context clear 698 query 700 set 703 status 701 Reference Manual 838 IF Prolog V5 3 Index esize 309 eused 309 evaluate expression 753 exception handle 166 236 intercept 131 166 raise 233 Execute a Prolog goal 638 exp 309 exponentiation 309 export predicates 241 349 expression arithmetic 820 compare 55 compute 55 converting to normal structure 813 evaluate 309 syntax 810 extended term stack size 309 used 309 FAIL port 644 FAILBODY port 644 FAILMATCH port 644 file check access permission 245 check existence 245 edit 223 file information 273 599 600 fixed point number syntax 803 float 309 floating point expression test 753 floating point number generate 767 query format 253 set format 253 syntax 803 test 252 752 unify 784 float_fractional_part 309 float_integer_part 309 floor 309 Force current subgoal to succeed 643 Force the current subgoal to fail 644 function 820 arithmetic 309 820 logical 309 820 garbage collection activate 264 global stack size 309 used 309 global variable define 427 482 807 delete 595 name 806 pop value 403 push value 427 query names 179 query value 276 403 set value 482 value 807 goal all solutions 118 249 499 call 125 127 call automatically 420 debug 205 profile 415 trace 573 true 243 580 go
537. query is successful A variable instantiation made during a program run will remain in force and cannot be overwritten until backtracking takes place which backtracks before the goal which instantiated the variable This means for example that queries such as user 9 N 5 Nis N 1 will always lead to a failure in Prolog N is instantiated to the constant 5 and 5 is 5 1 cannot be satisfied To avoid this failure you have to use an additional variable which is instantiated to the result of the addition operation user 79 N 5 Mis N 1 N 5 M 6 yes Variable names Variables are identified syntactically by a name The variable name is a character sequence made up of letters digits and underscore char acters and beginning with an uppercase letter or underscore character On its own an underscore character _ stands for an anonymous variable Scope of a variable The scope of a variable is a clause within this clause variables with the same name are identical Variables having the same name but occurring in different clauses are different variables IF Prolog V5 3 805 Reference Manual Prolog Syntax Terms Anonymous variable In Prolog a special role is played by the anonymous variable which is indicated syntac tically by _ underscore character Each occurrence of _ corresponds to a different variable even within a clause _ does not stand for one and the same object Wherever a variable is
538. r Predicate debug_config 3 Configure the debugger debug_config Parameter Old New The predicate debug_config 3 is used to query and modify debugger parameters Parameter is used to specify the debugger parameter to be queried or modified At the time of the call Old is unified with the previous value of the debugger parameter and then if unification was successful the new value New is set The following debugger parameters are available default values are printed in boldface Parameter call exit redo fail error wakeup suspend trymatch failmatch enterbody exitbody redobody failbody display_depth history trace Value on off on off on off on off on off on off on off on off on off on off on off on off on off 7 on off Description The interactive debugger stops at each CALL port implicit breakpoint The interactive debugger will not normally stop at the CALL port unless a user defined breakpoint ex ists or an execute command requires it to the same applies to the EXIT port the same applies to the REDO port the same applies to the FAIL port the same applies to the ERROR port the same applies to the WAKEUP port the same applies to the SUSPEND port the same applies to the TRYMATCH port the same applies to the FAILMATCH port the same applies to the ENTERBODY port the same applies to the EXITBODY port the same applies to the REDOBODY port the same
539. r could not be executed successfully due to a lack of memory Hints The call of TermUnifyFunctor Term Functor Arity is except for optimization identical to TermUnify Term TermMakeFunctor Functor Arity Example The following simple C function realizes a predicate mk_struct 3 which makes a struc ture with variables as arguments from given name and arity IF Prolog V5 3 785 Reference Manual Active C interface C Function Term Unify Functor include cpred h BOOLEAN mk_struct_3 void xx mk_struct Functor Arity Structure STRING string long value return TermIsAtom PrologArg 1 amp string amp amp TermIsInteger PrologArg 2 amp value amp amp TermUnifyFunctor PrologArg 3 string value void Cboot void CPRIM mk_struct 3 mk_struct_3 is See also TermUnifyCompound TermUnifyUniversal TermUnify TermMakeFunctor Reference Manual 786 IF Prolog V5 3 TermUnifyInteger C Function Active C interface Unify term with integer include cpred h BOOLEAN TermUnifyInteger TERM Term long Value The function TermUnifyInteger unifies the term Term with a term corresponding to the integer Value If unification is successful the function returns TRUE otherwise it returns FALSE Arguments Term Term variable Value Number with which the term is to be unified Hints The call of TermUnifyInteger Term Wert is exce
540. r but is a term of another type type_error atom The argument Assoc or Name must be a variable or an atom but is a term of another type Hints The sequence of solutions is undefined if current_op 3 has several solutions for the current call Operators are not associated with a module but are globally visible Example Output of all operators Reference Manual 186 IF Prolog V5 3 current _op 3 Predicate Input output for terms user current_op V T N lt ENTER gt writeq op V T N nl fail lt ENTER gt op 1000 xfy op 50 xfx op 100 xfx op 200 fy op 200 xfy op 200 xfx op 400 yfx rdiv op 400 yfx gt gt op 400 yfx lt lt op 400 yfx rem op 400 yfx mod op 400 yfx op 400 yfx op 400 yfx op 500 yfx op 500 yfx op 200 fy op 500 yfx op 200 fy op 500 yfx op 700 xfx op 700 xfx op 700 xfx lt op 700 xfx lt op 700 xfx gt op 700 xfx gt op 700 xfx op 700 xfx op 700 xfx op 700 xfx lt op 700 xfx lt op 700 xfx gt op 700 xfx gt op 700 xfx op 700 xfx op 700 xfx op 700 xfx op 700 xfx is op 900 xfx gt op 900 fy op 900 fy not op 1050 xfy gt op 1100 xfy IF Prolog V5 3 187 Reference Manual Input output for terms Predicate current _op 3 op 1100 xfx from op 1150 fx reexport op 1150 fx export op 1
541. r applications intended for third parties IF Prolog V5 3 213 Reference Manual Database Predicate debug_mode 3 Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also abolish 1 debug 0 trace 0 dynamic 1 modify_mode 3 Reference Manual 214 IF Prolog V5 3 default _editor 2 Predicate Operating system Query and set the editor default_editor EditorOld EditorNew The predicate default_editor 2 unifies EditorOld with the name of the editor currently If unification succeeds the setting is changed to EditorNew The editor is used by edit 0 1 Arguments EditorOld Atom EditorNew Atom Exceptions instantiation_error The argument EditorNew must not be a variable but a variable was specified type_error atom The argument EditorNew must be an atom but is a term of another type type_error atom The argument EditorOld must be a variable or an atom but is a term of another type Hints With the environment variable EDITOR it is possible to determine which editor is set at system startup If the variable is not set vi is set The setting is changed to the required value irrespective of whether the specified name represents a usable editor or not Example Query the current editor user default_editor E E lt ENTER gt E vi lt ENTER gt yes Set a new editor
542. r number to syntax error message Parse a goal string and store the information Get Prolog module Functionality Create passive Prolog goal Release passive Prolog goal Activate a passive Prolog goal Reference Manual IF Prolog V5 3 C interface Overview by functionality Raise errors C Function void ErrorContext Clear void BOOLEAN ErrorContextGet ERRORCLASS Error class STRING Parml STRING Parm2 ARITY Argno TERM Culprit BOOLEAN ErrorContextIsSet void void ErrorContextSet ERRORCLASS Errorclass STRING Parm1 STRING Parm2 ARITY Argno TERM Culprit Unification C Function BOOLEAN TermUnify TERM Terml TERM Term2 BOOLEAN TermUnify Atom TERM Term STRING Name BOOLEAN TermUnifyCompound TERM Term STRING Functor ARITY Arity BOOLEAN TermUnifyFloat TERM Term double Value BOOLEAN TermUnifyFunctor TERM Term STRING Functor ARITY Arity BOOLEAN TermUnifyInteger TERM Term long Value BOOLEAN TermUnifyList TERM Term TERM Head TERM Tail BOOLEAN TermUnifyNil TERM Term Functionality Clear error context Query error context Status of the error context Set error context Functionality Unify terms Unify term with atom Unify term with structure Unify term with floating point number Unify term with structure Unify term with integer Unify term with list Unify term with the empty list IF Prolog V5 3 689 Reference Manual Overview
543. r type domain_error on_or_off The argument Switch must be one of the atoms on or off but is another atom domain_error arity The command trace 0 1 was called with an incorrect number of parameters Hints The trace output is formatted in accordance with the interface Therefore the output of the command depends on the interface IF Prolog V5 3 667 Reference Manual Command interface Debugger command Set trace ports trace_port Ports Switch tp Ports Switch The trace_port 2 is used to set the trace ports One of the following atoms or a list of atoms may be specified as the port s Port Abbreviation Meaning call c CALL port enterbody eb ENTERBODY port fail f FAIL port failbody fb FAILBODY port failmatch fm FAILMATCH port redo r REDO port redobody rb REDOBODY port suspend S SUSPEND port trymatch tm TRYMATCH port wakeup Ww WAKEUP port exit x EXIT port exitbody xb EXITBODY port error er ERROR port The following designations may be used for frequently used combinations of ports call enterbody fail failbody failmatch redo redobody suspend trymatch wakeup exit exitbody error all in ner outer c eb fb fm Ir IrbIsi tmIw Ix xb ler Designation Meaning all all ports inner enterbody failbody failmatch redobody trymatch exitbody outer call fail redo wakeup suspend exit error Arguments Ports Atom or list of atoms Switch Atom on off
544. rIn which is not enclosed in single or double quotes or which is used in a character constant is to be replaced by the character CharacterOut Character conversion only takes place if the Prolog flag char_conversion is set to on Otherwise character conversions are stored but do not affect the reading of terms The definition of a character conversion is global i e it is not limited to the reading of one Prolog text Arguments CharacterIn Character CharacterOut Character Exceptions instantiation_error The argument CharacterIn or CharacterOut must not be a variable but a variable was specified type_error character The argument CharacterIn or CharacterOut must be a character but is a term of another type representation_error character The argument CharacterIn or CharacterOut is not representable as a single char acter Standard This predicate complies with the definition of the ISO standard for Prolog See also current_char conversion 2 IF Prolog V5 3 135 Reference Manual Input output for terms Directive char_conversion 2 Define a character conversion directive char_conversion CharacterIn CharacterOut The directive char_conversion 2 defines a character conversion It functions in exactly the same way as the predicate char_conversion 2 As as directive it is executed by consult 1 reconsult 1 or compile 1 when a Prolog source text is read and takes effect immediately Argument
545. rd This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also device_control 2 stream_device 2 current_stream_control 3 IF Prolog V5 3 177 Reference Manual Stream processing Predicate current _error 1 Query current error output stream current_error Stream The predicate current_error 1 unifies Stream with the current error output stream Arguments Stream Stream system defined term Exceptions domain_error stream The argument Stream must be a variable or an input output stream supplied by open 3 4 Hints The predicate current_error 1 will never unify Stream with an alias or the filename that was possibly used with error_tell 1 or open 4 Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also current_input 1 current_ouput 1 error_telling 1 set_input 1 set_output 1 set_error 1 Reference Manual 178 IF Prolog V5 3 current_global 1 Predicate Global variables Query global variables current_global Name Module The predicate current_global 1 unifies Name by backtracking with all the global variables defined in the calling module or in the specified Module The predicate current_global 1 succeeds by backtracking for all the global variables which were def
546. rd for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also clear_eol 0 1 clear_eos 0 1 IF Prolog V5 3 149 Reference Manual Stream processing Predicate close 1 2 Close an input output stream close Stream close Stream Actions The predicate close 1 closes the input output stream Stream Beforehand any buffer contents for an output stream are flushed All aliases associated with this Stream are deleted If Stream is the current input output or error output stream it is reset to user_input user_output or user_error The default streams opened by IF Prolog cannot be closed but close 1 succeeds neverthe less The predicate close 2 acts in the same way as close 1 except that the specified Actions are considered The list Actions may contain the following elements force false If it is not possible to close the Stream properly it should remain open force true If it is not possible to close the Stream properly this should be forced even if it means a loss of data default Arguments Stream Stream system defined term or alias atom Actions List of structures Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or
547. re considered by the Prolog system to be user arguments even if the name is the same as that of a system argument The end of the system arguments is also considered to have been reached if the command line contains an argument which is not a system argument IF Prolog V5 3 11 Reference Manual Prolog system System command prolog Exceptions Prolog license keyinformation missing Prolog can not be started because no license information could be found could not initialize PROLOG Prolog could not be initialized illegal size for Option The value for Option is not legal Parameter root not set correctly The parameter pathname in the option root pathname is not the name of the valid Prolog system directory or this directory cannot be accessed environment variable PROROOT not set correctly The path name defined by the environment variable PROROOT is not the name of the valid Prolog system directory or the directory cannot be accessed 3 Parameter r not set correctly The file file selected by the option r file is not a valid save state See also program_parameters 1 system_parameters 1 user_parameters 1 current_prolog_flag 2 Reference Manual 12 IF Prolog V5 3 proopt System command Prolog system Invoke the Prolog optimizer proopt Filename The command proopt optimizes the system state saved in the file Filename by optimizing all static user defined predicates The save
548. re included in the tree Notation specifying the module in which it was defined Request to the Prolog system to prove one or more goals Relation or object which is based on itself The proof method of Prolog Statement in the form If A then B term in the database in the form B A where A is the rule body and B the rule head A non logical effect of a built in predicate such as input output arithmetic evaluation or database modification Type of memory usage the values are pushed onto the stack and the last value stored is the first value processed again Description of a situation which can be either exactly true or IF Prolog V5 3 833 Reference Manual Glossary Appendix C static predicate stream structure subgoal term trail stack user predicate unification exactly false Predicate which may not be modified Unique designation for an open input output channel to a file terminal or printer for example This designation is created by the Prolog system and can also be referenced by means of a user defined alias name Term consisting of a functor and a sequence of arguments The number of arguments is the arity of the term A structure is written in functor notation as follows functor followed with out intervening space by an opening left parenthesis followed by comma separated arguments and a closing right parenthesis If the arity is zero the term is also referred to as an atom and is
549. re used to control loading to structure the Prolog text in modules or to declare properties of Prolog objects All directives are described in greater detail in the alphabetic section of this manual Grammar rules are also clauses which provide a special syntactical form to make work with grammars easier see IF Prolog User s Guide 2 IF Prolog V5 3 821 Reference Manual Prolog Syntax Prolog text Clause literal literal goal Directive literal Grammar rule literal gt production literal terminals gt production Goal variable literal moduleName literal literal module goal goal goal goal goal gt goal goal gt goal goal call goal call goal Q module not goal goal true fail moduleName literal module Reference Manual 822 IF Prolog V5 3 Prolog text Prolog Syntax Literal atom structure Module atom variable ModuleName atom Production literal terminal production production production production t goal Terminals term term 1 IF Prolog V5 3 823 Reference Manual Prolog Syntax Prolog text Reference Manual 824 IF Prolog V5 3 Appendix A ISO Standard Directives and Predicates Following directives are part of the ISO Standard
550. reakpoints that are set are assigned unique numbers that can be used in the commands remove_stop 1 activate_stop 1 and deactivate_stop 1 The numbers can be displayed by means of the view_stops 0 command See also remove _stop 0 1 activate_stop 0 1 deactivate_stop 0 1 view_stops 0 IF Prolog V5 3 665 Reference Manual Command interface Debugger command system 0 Interrupt interactive debugger and start the shell system S The system 0 command interrupts the debugger session and starts a shell The command is equivalent to call system The debugger session is resumed once the shell is terminated Exceptions domain_error arity The command system 0 was called with an incorrect number of parameters See also call 1 predicate system 0 Reference Manual 666 IF Prolog V5 3 trace 0 1 Debugger command Command interface Logging passes through ports trace t trace Switch t Switch The trace O is used to log passes through the current port If the argument value on is specified for Switch in the trace 1 command all passes through ports for which on has been specified for tracing are to be logged If off is specified trace logging is deactivated Arguments Switch Atom on off Exceptions instantiation_error The argument Switch must not be a variable but a variable was specified type_error atom The argument Switch must be an atom but is a term of anothe
551. rectives are also output as error messages on the error output stream Un known directives are reported by the error message domain_error directive In the event of errors in a module interface the affected module is deleted after Filename has been processed If there are errors in the declaration part of a module body the affected module body is deleted after Filename has been processed When initialization directives are executed see init 1 any exception may arise These aborts the execution of the initialization goal but does not abort the load process In addition warnings are output as a function of the Prolog flag warnings in certain situations to alert you to possible sources of errors Reference Manual 164 IF Prolog V5 3 consult 1 Predicate Database Hints If Filename does not contain the extension pro and if a file of this name cannot be found the extension pro is appended and the resultant filename used The predicate consult 1 is a metapredicate and manipulates the database in the calling module or in the specified Module If Filename contains module definitions then database manipulation takes place in these modules If not it is implicitly assumed that the contents of Filename belong to the body of the calling module or of the specified Module The difference compared with an explicitly specified body 1 directive at the start of Filename is that the associated body of the module is not first deleted
552. redicate Execution control Generate a new input loop break The predicate break O generates a new input loop of IF Prolog Thus input loops can be nested The input prompt shows the current nesting depth for input loops from level 2 onward e g user 2 This predicate enables the user to suspend the current goal and enter a dialog with IF Prolog When the new input loop is terminated the suspended goal is resumed An input loop is terminated when the atom end_of_file is entered or when an equivalent key e g CTRL is pressed abort 0 returns to the toplevel input loop of IF Prolog uo Hints The input loop of IF Prolog defines a context see context 2 which intercepts all the exceptions that are not handled directly The occurrence of errors or exceptions does not therefore lead to the abandonment of the IF Prolog input loop This predicate is not part of the IF Prolog runtime system and is therefore not available for applications intended for third parties Example user break lt ENTER gt user 2 lt EOF gt user Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also abort 0 set_default_module 1 current_default_module 1 IF Prolog V5 3 123 Reference Manual String processing Predicate byte_length 2 Count the bytes in an atom byte
553. redicate assertz 2 acts in the same way as assertz 1 but inserts the clause formed from Head and Body Head Body in the database Arguments Clause Structure atom Head Structure atom Body Term Exceptions instantiation_error The argument Head or Clause must not be a variable but a variable was specified type_error callable The argument Head Body or Clause must have the syntactical structure of a Prolog goal permission_error modify static_procedure The argument Head or the head of Clause specifies an existing predicate which has not been declared as dynamic and therefore cannot be modified permission_error access calling_context The argument Body or the body of Clause contains a call involving calling_con text 1 in a predicate that is not a metapredicate Hints The predicates consult 1 and reconsult 1 use assertz 2 3 to insert clauses in the database if the Prolog flag debug has the value off The predicate assertz 1 2 is a metapredicate and manipulates the database in the calling module or in the specified Module Reference Manual 88 IF Prolog V5 3 assertz 1 2 Predicate Database Standard Only the predicate assertz 1 complies with the definition of the ISO standard for Prolog See also asserta 1 2 clause 2 retract 1 2 assertz_with names 1 2 modify_mode 3 IF Prolog V5 3 89 Reference Manual Database Predicate assertz_with_names 2 3 Insert a clause in the database assertz_with_
554. redicate is not part of the IF Prolog runtime system and is therefore not available for applications intended for third parties Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also call 1 debug_begin 0 debug_end 0 trace 1 set_prolog_flag 2 Reference Manual 206 IF Prolog V5 3 debug_begin 0 User definable predicate Debugger User defined debugger initialization debug_begin Body The predicate debug_begin O is not a built in predicate but one which can be defined by the user It is called in the module in which debug 1 was called It is called automatically by debug 1 when the debugger is started The user can define debug_begin 0 to perform preliminary activities such as defining default breakpoints with debug_config 3 when the debugger is started Hints Nested calls involving debug 1 and or trace 1 are ignored If debug 1 is called several times during a goal execution debug_begin O is called each time This predicate is not part of the IF Prolog runtime system and is therefore not available for applications intended for third parties Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also debug 1 debug_end 0 debug_config 3 IF Prolog V5 3 207 Reference Manual Debugge
555. redicate system 1 succeeds otherwise if command execution is interrupted an exception occurs The predicate system 2 acts in the same way as system 1 and unifies ExitStatus with the exit status of the executed command see halt 1 Arguments Command Atom ExitStatus Integer Exceptions instantiation_error The argument Command must not be a variable but a variable was specified type_error atom The argument Command must be an atom but is a term of another type type_error integer The argument ExitStatus must be a variable or an integer but is a term of another type system_error command_failed A command passed to the operating system or a corresponding operating system function could not be executed successfully Hints This predicate is system dependent and may not be available on all operating systems The predicates system 1 2 are based on the C function system 3C see 10 i e Command may contain any file redirections metacharacters for filename generation etc that are normally permitted for the command interpreter Reference Manual 552 IF Prolog V5 3 system 1 2 Predicate Operating system Example user system date lt ENTER gt Thu Jul 14 09 46 07 DST 1994 yes user system ls l pro fgrep example lt ENTER gt lt EWorW gt 1 bre prolog 19 Jul 14 09 45 example pro yes user system cal 10 1996 lt ENTER gt October 1996 S MTu WTh F S 1 2 3 4 5 6
556. redicate told 0 resets the default output stream user_output as the current output stream If the earlier current output stream was not a default stream and is not simultaneously the current error output stream it is closed see close 1 Hints All output predicates which do not have an explicit stream argument refer to the current output stream This stream can always be addressed via the built in alias current_ output as well Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also tell 1 telling 1 current_output 1 set_output 1 close 1 2 Reference Manual 572 IF Prolog V5 3 trace 1 Predicate Tracing Activate tracing for a goal trace Goal Module The predicate trace 1 activates the tracer for executing Goal Before Goal is executed the user defined predicate trace_begin O is called if it is visible in the calling module or in the specified Module After Goal has been executed the user defined predicate trace_end 0 is called if it is visible in the calling module or in the specified Module Arguments Goal Goal Exceptions instantiation_error The argument Goal must not be a variable but a variable was specified type_error callable The argument Goal must have the syntactical structure of a Prolog goal existence_error procedure In executing Goal a predicate was to be act
557. registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error input stream The argument Stream is not a stream which has been opened for input open mode read permission_error input binary_stream The current input stream or the argument Stream must be a text stream but is associated with a binary stream permission_error past_end_of_stream The open option eof_action error was set for the input stream Stream and the end of the stream has already been reached system_error read ie neal The error indicated was reported by the operating system when reading the input stream Stream IF Prolog V5 3 271 Reference Manual Elementary input output Predicate get_code 1 2 type_error integer The argument CharCode must be a variable or an integer but is a term of another type representation_error in_character_code The argument CharCode must be a variable an integer representing a character code or the integer 1 representation_error character The entity read from the stream is not representable as a single character Example Reading a sequence of bytes up to the end of the line ASCII code 10 user repeat get_code B write B nl B 10 lt ENTER gt abcde lt ENTER gt 97 98 99 100 101 10 B 10 lt ENTER gt yes Standard These
558. rence Manual 710 IF Prolog V5 3 ParseError C Function Assignment of syntax error number to syntax error message include cpro h STRING ParseError int Number The function ParseError determines the syntax error message associated with Number The function returns a pointer to a character string containing the error message If a Number for which no error message is known is specified the string unknown_syntax_ error is returned The following syntax errors may occur Number Message 1 expected 2 expected 3 end of comment expected 4 illegal character 5 start of term expected 6 unknown stand alone character T operator expected 8 in postfix operator or end of term expected 9 too large constant 10 or expected 11 expected 12 gt or or expected 13 or expected 14 illegal number 15 precedence error 16 expected 17 interrupt 18 i o error 19 illegal escape sequence 20 illegal character code 21 exceeded max_arity Arguments Number Integer IF Prolog V5 3 711 Passive C interface Reference Manual Passive C interface C Function ParseError Hints The structure component t_parse_context pc_errno is set by the function Parse Prolog with the error number when a syntax error is determined See also ParseProlog InitProlog EndProlog syntax_error 2 Reference Manual 712 IF Prolog V5 3 ParseProlog C Function Passive C interface Parse
559. rent module the built in module user becomes the current module The Module will then have neither an interface nor a body but its name will still be known see current_module 1 The built in module user is an exception to this rule If this module is deleted with unload 1 an empty module interface and an empty module body is created immediately Other built in modules cannot be removed with unload 1 Arguments Module Atom name of a module Exceptions instantiation_error The argument Module must not be a variable but a variable was specified type_error atom The argument Module must be an atom but is a term of another type existence_error module The argument Module is not the name of an existing module permission_error access system_module The predicate unload 1 must not be executed for a system module Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also compile 1 load 1 module 1 current_default_module 1 current_ module 1 Reference Manual 594 IF Prolog V5 3 unset_global 1 Predicate Global variables Delete a global variable unset_global Name Module The predicate unset_global 1 deletes the global variable Name in the calling module or in the specified Module The predicate unset_global 1 will succeed even if no global variable called Name exists Arguments
560. rm and whose tail is the empty list Reference Manual 60 IF Prolog V5 3 D Predicate Term conversion domain_error non_empty _list The argument List must be a non empty list but is empty representation_error max_arity The list length of the argument List must be less than or equal to 127 but is larger Hints The atom is built in as an infix operator Example Each structure can be converted into a list user f a b g c L lt ENTER gt L f a b g c lt ENTER gt yes user a b L lt ENTER gt L a b lt ENTER gt yes user f X f 1 lt ENTER gt X 1 lt ENTER gt yes Structures can be generated in order to form goals dynamically user read Func read Arg lt ENTER gt Goal Func Arg lt ENTER gt call Goal lt ENTER gt atom lt ENTER gt abcd lt ENTER gt Func atom Arg abcd Goal atom abcd lt ENTER gt yes IF Prolog V5 3 61 Reference Manual Term conversion Predicate i 2 Standard This predicate complies with the definition of the ISO standard for Prolog See also 2 2 atomic 1 unify_with_occurs_check 2 Reference Manual 62 IF Prolog V5 3 2 2 Predicate Term comparison Compare terms for identity Terml Term2 Term1 Term2 Terml Term2 Term1 Term 2 The predicate 2 succeeds if Term1 and Term2 are identical otherwise
561. rms in operator notation and if there are no parentheses to provide an unambiguous operator argument relationship a syntax error is reported e g a lt b a lt b A syntax error is also reported if there is a conflict in the associativity information e g if a left associative operator precedes a right associative operator with the same precedence Such problems can be avoided by using the appropriate parentheses Operators are not associated with a module but are globally visible Reference Manual 380 IF Prolog V5 3 op 3 Predicate Input output for terms Example An exclusive OR operator is to be defined The atom is to be reserved for this operation A typical file named example pro could then look like this op 1100 xfy Goal1 Goal2 not Goall Goal2 Goal1 Goal2 Goall not Goal2 The op 3 directive ensures that the operator can be used in the input file Since the operator remains available after the load operation it can be used after loading with consult 1 user example lt ENTER gt yes user member a member a a lt ENTER gt yes The evaluation of complex goals becomes critical if operators with the same precedence and different meanings appear together The operator for the OR function of Prolog is defined as op 1100 xfy If the database contains three simple facts a b and c evaluation is performed as follows user a b c lt ENTER gt
562. ror integer The argument EndPosition or Error must be a variable or an integer but is a term of another type type_error list The argument VarList must be a variable or a list but is a term of another type Furthermore if an arithmetic expression is specified for the argument StartPosition all the exceptions for is 2 can occur Example user parse_atom abc 1 P T V E lt ENTER gt P P 5 T abc V E 0 lt ENTER gt yes user parse_atom a c 1 P T V E lt ENTER gt k Syntax_error operator expected gt gt gt line 1 column 3 P 5 T _69 V 7O E 7 lt ENTER gt yes The first period in the string is the decimal point of a floating point number Parsing therefore ends with the second period user parse_atom A 1 3 1 P T V E lt ENTER gt 7 134 1 3 PA _134 0 lt ENTER gt ma lt Uu tol IF Prolog V5 3 393 Reference Manual Term conversion Predicate parse_atom 6 yes More then one term from a string can be parsed user Line_of_Terms a A b B lt ENTER gt parse_atom Line_of_Terms 1 P Y YY _ lt ENTER gt parse_atom Line_of_Terms P _ Z ZZ _ lt ENTER gt Line_of_Terms a A b B P 7 Y a _210 YY 7A 270 Z b _218 ZZ B _218 lt ENTER gt yes A period may be part of an atom which is made up of special characters There must therefore be a delimiter between a special
563. rpret this sequence as a single lexical element Separators in Prolog are blanks the end of line character comments Comments in Prolog may be one of two kinds e variable length comments e end of line comments 45 the tab character and The Prolog system registers comments merely as delimiters between lexical elements To the user they also serve for documentation purposes Variable length comments All characters from the pair to the occurrence of the pair are interpreted as a comment The comment may extend over more than one line Nested comments are prohibited if the Prolog flag nested_comments has the value off and allowed if the flag has the value on Comments may be included between lexical elements in Prolog texts wherever delim iters are permitted Thus a comment may even be inserted in Prolog normal structures or in lists X illness 25 probability flu End of line comments An end of line comment starts with the percent sign All characters between the percent sign and the end of the line are then interpreted as a comment Delimiters in normal structures and expressions e In normal structures delimiters are prohibited between the functor and the opening parenthesis e A delimiter must occur between an operator and a subsequent expression enclosed in parentheses If it is omitted Prolog will interpret the operator together with the expression in parenthesis as
564. ructure with the format Functor Arity but is a term of another type type_error atom The name of the predicate Predicate in PredicateList must be an atom type_error integer The arity of the predicate Predicate in PredicateList must be an integer domain_error not_less_then_zero The arity of the predicate Predicate in PredicateList must be a positive integer but is negative IF Prolog V5 3 241 Reference Manual Module concept Directive export 1 representation_error max_arity The arity of the predicate Predicate in PredicateList must be an integer in the range 0 127 but is larger permission_error modify procedure The predicate indicator Predicate in PredicateList specifies a predicate which al ready exists and is not modifiable or which is the name of a language construct permission_error directive module The specified directive export 1 is not valid in this position Hints The atom export is defined as a prefix operator Directives are evaluated during consultation see consult 1 reconsult 1 or compi lation see compile 1 procmp command Standard The directive export 1 is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also module 1 import 1 2 meta 1 private 1 reexport 1 2 Reference Manual 242 IF Prolog V5 3 fail 0 Language construct Execution control Initiate backtracking fail
565. ry March April May June July August September October November December if TermIsInteger PrologArg 1 amp number if 1 lt number amp amp number lt 12 return TermUnifyAtom PrologArg 2 names number 1 Reference Manual 704 IF Prolog V5 3 ErrorContextSet C Function Active C interface ErrorContextSet DOMAIN_ERROR month NULL 1 NULL return FALSE void Cboot void CPRIM month 2 month_2 See also ErrorContextClear ErrorContextGet ErrorContextIsSet IF Prolog V5 3 705 Reference Manual Passive C interface C Function fprintt Formatted output of Prolog terms and C data objects include cpro h size_t fprintt FILE FilePointer STRING Format The function fprintt is an extension of the C function fprintf see 10 for Prolog terms An argument in may be either a Prolog term or a normal C data object The arguments are printed in accordance with the formatting specifications in Format The output is printed on the stream FilePointer Arguments FilePointer File pointer Format Character string format specification see write_formatted 2 3 Prolog terms or C data objects in accordance with Format See also outputlen printt sprintt write formatted 2 3 Reference Manual 706 IF Prolog V5 3 InitProlog C Function Passive C interface Initialize IF Prolog and define the
566. s instantiation_error The argument List must not be a variable but a variable was specified type_error list The argument List must be a list but is a term of another type type_error list The argument ReversedList must be a variable or a list but is a term of another type Example user reverse z e u s R lt ENTER gt R s u e z lt ENTER gt yes user reverse 2 atom 5 6 f g Var L lt ENTER gt Var _70 _70 f g 5 6 atom 2 lt ENTER gt Il yes user reverse X lt ENTER gt X lt ENTER gt yes IF Prolog V5 3 463 Reference Manual List processing Predicate reverse 2 user Palindrome s a i p p u a k a u p p i a s lt ENTER gt reverse Palindrome Palindrome lt ENTER gt Palindrome s a i p p u a k a u p p i a s lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also append 3 member 2 Reference Manual 464 IF Prolog V5 3 save_module 1 Predicate Module concept Store current module in a file save_module Filename Module The predicate save_module 1 saves the calling module or the specified Module in the file named Filename If Filename does not contain the extension cmp the extension is appended and the resultant filename Filename cmp is used Arguments Filename Atom
567. s instantiation_error The argument Module or PredicateList or a subterm must not be a variable but a variable was specified IF Prolog V5 3 299 Reference Manual Module concept Directive import 1 2 type_error atom The argument Module must be an atom but is a term of another type existence_error module The argument Module is not the name of an existing module type_error list The argument PredicateList must be a regular list but is a term of another type or not regular type_error predicate_indicator The argument Predicate in PredicateList must be a predicate indicator i e a structure with the format Functor Arity but is a term of another type type_error atom The name of the predicate Predicate in PredicateList must be an atom type_error integer The arity of the predicate Predicate in PredicateList must be an integer domain_error not_less_then_zero The arity of the predicate Predicate in PredicateList must be a positive integer but is negative representation_error max_arity The arity of the predicate Predicate in PredicateList must be an integer in the range 0 127 but is larger permission_error modify procedure The predicate indicator Predicate in PredicateList specifies a predicate which al ready exists and is not modifiable or which is the name of a language construct existence_error procedure The argument Predicate in PredicateList specifies a predicate that was not ex ported fr
568. s CharacterIn Character CharacterOut Character Exceptions Errors in directives are detected with consult 1 reconsult 1 or compile 1 No exceptions are generated Instead only error messages are output on the current error output stream This directive can produce the following error messages instantiation_error The argument CharacterIn or CharacterOut must not be a variable but a variable was specified type_error character The argument CharacterIn or CharacterOut must be a character but is a term of another type representation_error character The argument CharacterIn or CharacterOut is not representable as a single char acter Hints Directives are evaluated during consultation see consult 1 reconsult 1 or compi lation see compile 1 procmp command Character conversions take effect immediately as soon as the directive is evaluated provided that the Prolog flag char_conversion is set to on Standard The directive char_conversion 2 complies with the definition of the ISO standard for Prolog Reference Manual 136 IF Prolog V5 3 char_conversion 2 Directive Input output for terms See also current_char_conversion 2 IF Prolog V5 3 137 Reference Manual Operating system Predicate chdir 1 Change current directory chdir Dir The predicate chdir 1 changes the current directory for the IF Prolog process The predi cate succeeds if Dir can be made the current directory
569. s also used by output of cyclic terms see 2 off Cyclic terms can be entered in the above notation but Variable is not unified with Term nested_comments off Nested comments are not allowed in a Prolog text Begin of a comment inside a comment is ignored which normally leads to a syntax error on Nested comments are accepted in a Prolog text write_depth 10 Maximal depth of terms output in the Prolog toplevel see break 0O This applies to variable instantiations of a query and to exception messages The predicate write_formatted 2 3 takes this value in account if a term is to be output with the format 4w The following Prolog flags can only be queried but not changed Their value depends on the command line parameters specified when the Prolog system was started see system_para meters 1 Flag Value Description signal on The system parameter nosignal was not specified off The system parameter nosignal was specified IF Prolog V5 3 193 Reference Manual System information Predicate current _prolog_flag 2 notty on The system parameter notty was specified off The system parameter notty was not specified iso on The system parameter iso was specified off The system parameter iso was not specified The following Prolog flags supply information on the implementation of the Prolog system or on the operating system the values cannot be changed Flag Description max_arity The value indicates the maximum ari
570. s an atom Single quotes must always occur in pairs List tail delimiter delimits the list tail from leading list elements End of a term in a Prolog input list functor or decimal point for floating point numbers Start of a comment which is terminated by end of line Identify the beginning and end of a comment Lexical elements and delimiters in Prolog In inputs Prolog makes a distinction between lexical elements and delimiters Reference Manual 794 IF Prolog V5 3 Basic Prolog elements Prolog Syntax Lexical elements When Prolog text is read with the predicate read 1 consulting or compiling syntactical analysis is performed The internal representation is built up from the lexical elements tokens of the Prolog language namely atoms variables integers in different notations floating point numbers rational numbers and the Prolog specific characters Atoms are character sequences which are used for example as names The following are valid atoms e character sequences beginning with a lowercase letter and consisting only of letters digits and underscores e character sequences consisting of special characters e g and e character strings enclosed in single quotes Variables are also sequences of letters digits and underscores which begin with an uppercase letter or with an underscore _ to distinguish them from atoms Integers are sequences of digits possibl
571. s not permitted for language constructs with the exception of ca11 1 The predicates activated in the goal must be visible in the specified Module unless the 2 qualification is used for such a predicate to indicate explicitly the module in which this predicate is visible The predicates activated in the goal are normally executed in the context of the module in which they are defined This does not apply to metapredicates which are executed Reference Manual 368 IF Prolog V5 3 not 1 Language construct Execution control in the context of the specified Module unless the 2 qualification is used for a meta predicate to indicate explicitly the module context in which this predicate is to be executed Example The language construct not 1 can be used to call a goal without variables being instan tiated user not not member Y a b lt ENTER gt Y _68 lt ENTER gt yes Standard This language construct is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also 1 call 1 fail 0 2 2 set prolog flag 2 IF Prolog V5 3 369 Reference Manual Term classification Predicate number 1 Test for number number TestTerm The predicate number 1 succeeds if TestTerm is an integer or a floating point number oth erwise it fails Arguments Test Term Term Hints If IF Prolog is configured with
572. s on off Description A message is output when a Prolog text is loaded No message is output when a Prolog text is loaded If input files are not specified using a complete path name they are searched for in the directories speci fied in the Paths list The default value of this Pro log flag is the value of the system parameter sp if specified otherwise it is the value of the environment variable PROPATH or it is empty Syntax errors found by analysis with read_term 2 3 etc raise an exception Syntax errors found by analysis with read_term 2 3 etc are reported directly by the parser in a message and the predicate fails Syntax errors found by analysis with read_term 2 3 etc are not reported and the predicate fails Syntax errors found by analysis with parse_atom 6 are reported directly by the parser in a message Syntax errors found by analysis with parse_atom 6 are not reported by the parser but can be queried with the read_error 2 3 predicates For consult 1 etc warnings are output for possible errors For consult 1 etc no warnings are output Reference Manual 488 IF Prolog V5 3 set_prolog_flag 2 Predicate System information unknown error If a predicate is to be activated which is not defined an exception is raised This does not apply to pred icates for which the exception mode has been set to on see predicate_mode 3 fail If a predicate is to be activated which is not defined
573. s required by the ISO standard are available The imple mentation specific extensions of IF Prolog are not available nobuf The standard input streams are not buffered by Prolog nocopyright The copyright message is not output when Prolog starts nonotify The initial value of the Prolog flag consult is set to nonotify This means that no messages are displayed on the screen when a file is loaded nosignal Prevents the Prolog system from managing signals itself i e no signal handling routines are defined The predicate signal_control 2 has no effect notty The standard streams screen and keyboard are not linked to the terminal but are mapped to the standard input and standard output In this case it is not possible to use the keyboard and the screen as the input output devices when the standard input output has been redirected nowarnings The initial value of the Prolog flag warnings is set to off prompt The initial value of the Prolog flag prompt is set to on stream Prolog acts as if no terminal is available The debugger is started without a graphical user interface see also debug_config 3 verbose A message containing configuration and license information and creation date of IF Prolog is output when Prolog starts xenv If a OSF Motif environment X server is available the Prolog system starts the graphical development environment under OSF Motif Identifies the end of the system arguments All following arguments a
574. ser_input user_output or user_error Stream1 will be redefined accordingly as the standard input output or error output stream The predicate can also be used for any streams that have been opened for the same I O mode read or write provided their device drivers support the required commands If Stream2 is associated with an open file it will be closed before Stream1 is copied Before that stream_control Stream2 update is called if the control command update is defined for this stream This allows the device driver to perform cleanup tasks After the operation both streams will access the same file Arguments Stream1 Stream system defined term or alias atom Stream2 Stream system defined term or alias atom Exceptions instantiation_error The argument Streaml or Stream2 must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream1 or Stream2 must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream or Stream2 must be associated with an open input output stream permission_error duplicate stream The argument Stream1 or Stream2 specifies an input output stream that is not suitable for the required operation permission_error input stream The argument Stream2 is not a stream which has been opened for input o
575. ses IF Prolog to be exited implementation_error TermMakeList out of memory The function TermMakeList could not be executed successfully due to a lack of memory Example The following simple C function realizes a predicate mk_list 3 which makes a list of integers up to a given limit include cpred h BOOLEAN mk_list_2 void mk_list Count List long max ij TERM list list TermMakeNil if TermIsInteger PrologArg 1 amp max return FALSE IF Prolog V5 3 771 Reference Manual Active C interface C Function TermMakeList for i max i gt 1 i list TermMakeList TermMakeInteger i list return TermUnify PrologArg 2 list void Cboot void CPRIM mk_list 2 mk_list_2 See also TermMakeNil TermIsList Reference Manual 772 IF Prolog V5 3 TermMakeNil C Function Active C interface Generate an empty list include cpred h TERM TermMakeNil void The function TermMakeNil generates an empty list and returns it as the result Example See example at TermMakeList See also TermMakeList TermIsNil IF Prolog V5 3 773 Reference Manual Active C interface C Function TermMakeUniversal Generate a Prolog structure include cpred h TERM TermMakeUniversal STRING Functor ARITY Arity TERM Args The function TermMakeUniversal generates a Prolog structure with the n
576. sfully In addition all the exceptions and error messages described for reconsult 1 may occur Example edit 0 1 cannot determine whether the editor set is in fact a command deserving the name user default_editor _ cat lt ENTER gt yes user edit example lt ENTER gt a b b true Should the file example pro be reconsulted y n y lt ENTER gt xxx reconsult example pro loaded in 0 02 sec yes Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso See also default_editor 2 Reference Manual 224 IF Prolog V5 3 end_module 0 1 Directive Module concept Conclude the definition of a module end_module end_module Module end_module Module The directive end_module 0 1 marks the end of the definition of the current module or the module Module The directive end_module 0 1 is used to complete as well the module interface as the module body The directive end_module 1 can only be used to conclude the definition of the current module This is why Module must be identical to the name of the current module The directive end_module O concludes the definition of the current module This assumes of course that a module is being defined when this directive is processed Once processing of the end_module 0 1 directive has been completed the system is lo
577. specified type_error list The argument List must be a list but is a term of another type type_error list The argument SortedList must be a variable or a list but is a term of another type Example Sorting occurs in the given order variables floating point numbers rational numbers integers atoms and structures user sort a a a 777 zzzz X L lt ENTER gt X _71 L _71 777 zzzz a a a lt ENTER gt yes Atoms are sorted in alphabetical order IF Prolog V5 3 527 Reference Manual List processing Predicate sort 2 user sort c b a d L lt ENTER gt L a b c d lt ENTER gt yes Numbers of equal type are sorted in arithmetic order user sort 3 4 56 2 L lt ENTER gt L 2 3 4 56 lt ENTER gt yes As in the case of comparison predicates for terms structures are sorted first by arity then by the name of the functor and finally by arguments from left to right user sort a a b a a a f a L lt ENTER gt L f a a a a a a b lt ENTER gt yes Care must be taken with variables user sort Z A L Z zzz A aaa lt ENTER gt Z ZZZ A aaa L zzz aaa lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also lt 2 gt 2 Reference Manual 528 IF Prolog V5 3 statistics 0 2 Predicate Memory management
578. ssion is specified for the argument Index all the exceptions for is 2 can occur Example user create_array Array 3 set_array Array 1 100 for 1 X 2 get_array Array 1 Valuel write first Valuel nl set_array Array 1 200 get_array Array 1 Value2 write second Value2 nl IF Prolog V5 3 477 Reference Manual Term classification Predicate set_array 3 first 100 second 200 first 100 second 200 Array array 200 0 0 X 2 Valuei 100 Value2 200 lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Compatibility V5 1A The predicate set_array 3 is new See also arg 3 array 1 2 create_array 2 get_array 3 Reference Manual 478 IF Prolog V5 3 set_default_module 1 Predicate Module concept Set current module set_default_module Module The predicate set_default_module 1 sets the current module to Module All goals entered in the input loop of IF Prolog see break 0 are executed in the context of the current module Arguments Module Atom name of a module Exceptions instantiation_error The argument Module must not be a variable but a variable was specified type_error atom The argument Module must be an atom but is a term of another type existence_error module The argument Module is not the name of an existi
579. st O Reference Manual 584 IF Prolog V5 3 unix_fork 1 Predicate Operating system test unix_fork Pid Pid 0 repeat unix_wait Pid test break halt yes On exiting this input loop the user is returned to the original process in its original unaltered state user test lt ENTER gt user 2 asserta a lt ENTER gt yes user 2 listing lt ENTER gt xxx user a O a user test O test unix_fork Pid Pid 0 by repeat unix_wait Pid f test program halt yes user 2 halt lt ENTER gt yes user listing lt ENTER gt IF Prolog V5 3 585 Reference Manual Operating system Predicate unix_fork 1 xxx user test O test unix_fork Pid Pid 0 La repeat unix_wait Pid test program halt yes See also the example in the section Process management and communication in the IF Prolog User s Guide 2 Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also exec 1 2 unix_wait 1 2 unix_kill 2 system 0 1 2 3 5 Reference Manual 586 IF Prolog V5 3 unix_getpid 1 Predicate Operating system Query process ID of current process unix_getpid Pid The predicate unix_getpid 1 unifies Pid with the process ID number of the IF Prolog pr
580. st number k K Set the initial size of the variable instantiations stack trail to number bytes If k or K after number is given it is set to number kilobytes If required for program execution the memory area is automatically increased msl number k K Set the initial size of the local data stack to number bytes Ifk or K after num ber is given it is set to number kilobytes If required for program execution the memory area is automatically increased msx number k K Set the initial size of the extended terms stack to number bytes If k or K after number is given it is set to number kilobytes If required for program execution the memory area is automatically increased ms number k K Set the initial size of the total memory of the Prolog system to number bytes If k or K after number is given it is set to number kilobytes If required for program execution the memory area is automatically increased mi number k K Set the minimum size of the memory blocks requested by the Prolog system to number bytes If k or K after number is given it is set to number kilobytes Reference Manual 10 IF Prolog V5 3 prolog System command Prolog system debug The initial value of the Prolog flag debug is set to on This means that all the predicates which you read into the database with consult 1 recon sult 1 or assert 1 2 are implicitly declared as dynamic thereby supporting the debugging of a program iso Only the feature
581. statements in the style of the C preprocessor The input file contains Prolog code plus conditional expressions The output file will only contain those parts of the Prolog code that remain after evaluation of the conditional expressions If the file Filename exists and is readable this is the input file Otherwise if Filename does not already have a ppp suffix the suffix ppp will be appended to Filename This is then the name of input file The name of the output file will have the suffix pro If the name of the input file does have the suffix ppp pro will replace ppp Otherwise pro will be appended to the name of the input file Please note that prior contents of the output file will be overwritten After successful preprocessing the preprocessor exits with the exit value 0 If an error occurs a message is printed and the preprocessor exits with the exit value 1 The following flags are allowed on the command line Datom atom is defined as an atom to be used in conditional expressions in the input file The following directives are allowed in conditional statements The directives must begin at the first column of the input file if lt expression gt ifdef lt atom gt ifndef lt atom gt elif lt expression gt else endif The syntax of expressions is lt expression gt lt expression gt lt expression gt lt expression gt amp amp lt expression gt lt expression gt lt expression gt
582. stem predicate Remove a predicate from the database System predicate Return to the toplevel loop of IF Prolog These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso Reference Manual 292 IF Prolog V5 3 help 0 1 Predicate System information See also manual 0 1 IF Prolog V5 3 293 Reference Manual Net communication Predicate host_addr 2 Query names or addresses of host host_addr Host Addr host_addr Host Addr The predicate host_addr 2 establishes the relationship between host name and host address A distinction is made between two cases 1 Host is instantiated The argument Addr must be a variable or an atom It is unified by backtracking with the Internet address es of the host whose hostname is Host Normally a machine has only one Internet address 2 Host is uninstantiated The argument Addr must be an atom The argument Host is unified by backtracking with the standard and alias names of the host whose Internet address is Addr The names and addresses are obtained either from the name server named the NIS service or the hosts database on UNIX etc hosts or etc inet hosts Arguments Host Atom Addr Atom Exceptions type_error atom The argument Host or Addr must be a variable or an atom but is a term of another type domain_error hostname The argument Host does not
583. struct complies with the definition of the ISO standard for Prolog See also 1 0 true 0 Reference Manual 244 IF Prolog V5 3 file_test 2 Predicate Operating system Check access permission for a file file_test Pathname AccessMode The predicate file_test 2 checks whether a file or a directory with the name Pathname can be accessed in the way defined by AccessMode If this is possible file_test 2 succeeds otherwise it fails There are two possible entries for AccessMode read Test if Pathname can be accessed in read mode i e a file or a directory with this name exists and the user has the necessary permission for read access write Test if Pathname can be accessed in write mode i e either a file or a directory with this name exists and the user has the necessary permission for write access or the user has the authority in the relevant directory to create files Arguments Pathname Atom AccessMode Atom read write Exceptions instantiation_error The argument Pathname or AccessMode must not be a variable but a variable was specified type_error atom The argument Pathname or AccessMode must be an atom but is a term of another type domain_error access_mode The argument AccessMode does not specify a valid access mode for a file Hints The predicate file_test 2 does not open any files It can establish whether a later open 3 4 could be successful for Pathname With access mode re
584. structure which is to receive type dependent infor mation on a term see cpred h Hints Future versions of IF Prolog will extend the definitions of the data types TERMTYPE and TERMINFO If the TermDecompose function is used the user should make sure that the function can also return a value that is not currently defined as the result Example The following simple C function realizes a predicate type_of 3 which gives the type and more information about a term include cpred h BOOLEAN type_of_3 void k type_of Term Type Info TERMINFO terminfo TERM info STRING typename info PrologArg 1 switch TermDecompose PrologArg 1 amp terminfo case TERM_VAR typename var break case TERM_INTEGER typename integer break case TERM_FLOAT typename float break case TERM_ATOM typename atom break case TERM_COMPOUND typename compound IF Prolog V5 3 747 Reference Manual Active C interface C Function TermDecompose info TermMakeCompound 2 TermMakeAtom terminfo compound functor TermMakeInteger terminfo compound arity break default typename unknown return TermUnifyAtom PrologArg 2 typename amp amp TermUnify PrologArg 3 info void Cbhoot void CPRIM type_of 3 type_of_3 See also TermType TermArg Reference Manual 748 IF Prolog V5 3 TermIsAtom C Function Active C interface Tes
585. system defined term or alias atom Line Integer Column Integer Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error input stream The argument Stream is not a stream which has been opened for input open mode read type_error integer The argument Line or Column must be a variable or an integer but is a term of another type Standard These predicates are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso IF Prolog V5 3 247 Reference Manual Stream processing Predicate filepos 2 3 See also open 3 4 Reference Manual 248 IF Prolog V5 3 findall 3 Predicate Execution control Find all solutions of a goal findall Term Goal TermList Module The predicate findall 3 unifies TermList with a list which contains the same number of instantiations of Term as there are solutions for Goal If Goal fails TermList is unified with the empty list After goal execution all the variables which occur in Term and Goal are u
586. system module Hints The predicate modify_mode 3 is a metapredicate and manipulates the database in the calling module or in the specified Module A predicate may have certain attributes which when it is created are set implicitly by the system according to the current environment or declarations They can be modified to a certain extent explicitly by the user These include the following e List mode see list_mode 3 e Debug mode see debug_mode 3 e Exception mode see predicate_mode 3 e Modification mode see modify_mode 3 These attributes are retained even if the predicate is deleted with abolish 1 for ex ample Reference Manual 352 IF Prolog V5 3 modify_mode 3 Predicate Database Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also abolish 1 dynamic 1 debug_mode 3 list mode 3 predicate_mode 3 IF Prolog V5 3 353 Reference Manual Module concept Directive module 1 Define a module module Module module Module The directive module 1 defines a new module and marks the start of the module interface The module interface ends with an end_module 0 1 directive the start of the module body begin_module 1 the start of a new module interface module 1 or the end of the file If there is already a module with the name Module which is not a system module this mod
587. t Day lt 31 DoW Integer 1 lt DoW lt 7 DoY Integer 1 lt DoY lt 366 Hour Integer 0 lt Hour lt 23 Min Integer 0 lt Min lt 59 Sec Integer 0 lt Sec lt 59 Exceptions instantiation_error The argument Time must not be a variable but a variable was specified type_error integer The argument Time must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer type_error integer The argument Year Month Day DoW DoY Hour Min or Sec must be a variable or an integer but is a term of another type Furthermore if an arithmetic expression is specified for the argument Time all the exceptions for is 2 can occur Reference Manual 332 IF Prolog V5 3 localtime 9 Predicate Operating system Hints The current system time is made available by the zero arity arithmetic function time mostly as the time in seconds since 1 1 1970 GMT If the operating system environment is correctly configured then conversion by local time 9 will take account not only of time zone differences but also of daylight saving time The predicate is based on the C function localtime 3C see 10 Example user localtime time Year Month Day lt ENTER gt DoW DinY Hrs Min Sec lt ENTER gt Year 1997 Month 1 Day 8 DoW 3 DinY 8 Hrs 16 Min 3 Sec 16 lt ENTER gt yes Standard This predicate is not required by the
588. t output for terms Predicate write_term 2 3 quoted true nl lt ENTER gt new nline yes user write_term a b tc nl lt ENTER gt ax btec yes user write_term a b c lt ENTER gt ignore_ops true nl lt ENTER gt a b c yes user write_term f X Y n1 lt ENTER gt f _68 _69 X _68 Y _69 lt ENTER gt yes user write_term f X Y lt ENTER gt varnames X X Y Y nl lt ENTER gt f X Y X _68 Y _69 lt ENTER gt yes user write_term VAR 0 VAR 54 lt ENTER gt numbervars true nl lt ENTER gt A C2 yes Standard These predicates comply with the definition of the ISO standard for Prolog The options maxdepth portrayed and varnames are not required by the ISO standard for Prolog Therefore they are not available in ISO compatibility mode see Prolog flag iso Reference Manual 616 IF Prolog V5 3 write_term 2 3 Predicate Input output for terms See also print 1 2 write 1 2 writeq 1 2 write_canonical 1 2 IF Prolog V5 3 617 Reference Manual Input output for terms Predicate writeq 1 2 Output a term in readable form writeq Term writeq Stream Term The predicate writeg 1 outputs Term on the current output stream Existing operator definitions are taken into account The predicate writeq 2 acts in the same way as writeg 1 but
589. t 3 accepts a connection from a client The argument Socket specifies a stream socket opened by socket 3 which has been bound to an address by socket_bind 2 and is listening to connections by socket_listen 1 2 socket_accept 3 extracts the first connection on the queue of pending connections and creates a new socket with the same properties as Socket The argument NewSocket is instantiated to the identification of the new socket The argument Addr is unified with the address of the connecting entity The address for internet domain socket has the form Host Port where Host is the name of the receiving machine and Port is the port number The address for unix domain socket is an atom Filename Arguments Socket Socket system defined term Addr Structure Host Port or atom Filename Host Atom Port Integer Filename Atom NewSocket Socket system defined term Exceptions instantiation_error The argument Socket must not be a variable but a variable was specified type_error socket The argument Socket must be a socket supplied by socket 3 but is a term of another type domain_error socket The argument Socket must be a currently open socket supplied by socket 3 domain_error stream_socket The argument Socket must be a stream socket but is a socket of another type domain_error bound_socket The argument Socket does not specify a socket which has been bound to an address type_error host port The argument Addr m
590. t Atom or IntegerList Port Integer Filename Atom List List of integers or integer expressions Exceptions instantiation_error The argument Socket Addr or List or a subterm must not be a variable but a variable was specified type_error socket The argument Socket must be a socket supplied by socket 3 but is a term of another type domain_error socket The argument Socket must be a currently open socket supplied by socket 3 type_error host port The argument Addr must be a structure of the form Host Port but is a term of another type type_error atom The argument Host must be an atom but is a term of another type IF Prolog V5 3 523 Reference Manual Net communication Predicate socket_send 2 3 type_error integer The argument Port must be an integer but is a term of another type type_error atom The argument Filename must be an atom but is a term of another type domain_error file_name The value of the argument Filename is not a valid name for a file domain_error unix_socket _file The argument Filename must refer to a unix socket file but the file is of another type type_error list The argument List must be a list but is a term of another type type_error integer An element of List must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer representation_error character_code An element of List must be a
591. t for atom include cpred h BOOLEAN TermIsAtom TERM Term STRING Name The function TermIsAtom tests whether the term Term is an atom If it is the function sets Name to point to the name of the atom and returns TRUE Otherwise it sets the error context and returns FALSE In this case Name is not changed Arguments Term Term variable Name Pointer to a pointer to character string Exceptions instantiation_error The argument Term must not be a variable but a variable was specified type_error atom The argument Term must be an atom but is a term of another type Hints The pointer Name loses its validity when no term containing an atom or functor with this name can be accessed See also TermMakeAtom IF Prolog V5 3 749 Reference Manual Active C interface C Function TermIsCompound Test for structure include cpred h BOOLEAN TermIsCompound TERM Term STRING Functor ARITY Arity The function TermIsCompound tests whether the term Term is a structure with the functor Functor and the arity Arity If it is all the pointers to term variables made available in are initialized with term variables which contain the arguments of the structure Term The function then returns TRUE If Term is not a structure or its functor and arity do not match Functor and Arity respec tively the function sets the error context and returns FALSE Atoms are treat
592. t is a term of another type domain_error file_name The value of the argument Filename is not a valid name for a file permission_error open source_sink The argument Filename specifies a file or a different I O medium that cannot be opened system_error read system_error interrupted The error indicated was reported by the operating system when reading the input stream Filename Hints The atom include is defined as a prefix operator Directives are evaluated during consultation see consult 1 reconsult 1 or compi lation see compile 1 procmp command If Filename is not an absolute pathname the search for the file takes place relative to the directory of the file containing the include 1 directive If Filename does not contain the extension pro and if a file of this name cannot be opened for reading the extension is appended and the resultant filename is used Reference Manual 302 IF Prolog V5 3 include 1 Directive Database Standard The directive include 1 complies with the definition of the ISO standard for Prolog See also ensure_loaded 1 IF Prolog V5 3 303 Reference Manual String processing Predicate index 3 Determine the position of a character string in an atom index Atom String Position The predicate index 3 searches for the first occurrence of String in Atom The position at which index 3 finds String is unified with Position If String does not occur in
593. t is unified with the list of variables and their names as atoms found in Term in the form Name Variable If String starting at StartPosition is not a correct Prolog term then Term and VarList are not unified i e remain uninstantiated when variables are specified and Error is unified with the appropriate syntax error number see syntax_error 2 The Prolog flag report_ read_error see set_prolog_flag 2 can be used to control whether or not a syntax error message is to be output EndPosition is always unified with the integer that specifies the position in String at which parsing ends so that further parse_atom 6 calls if any can be continued from this position Arguments String Atom Start Position Integer or integer expression 0 lt StartPosition lt Length of String EndPosition Integer Term Term VarList List Error Integer gt 0 Exceptions instantiation_error The argument String or StartPosition must not be a variable but a variable was specified type_error atom The argument String must be an atom but is a term of another type Reference Manual 392 IF Prolog V5 3 parse_atom 6 Predicate Term conversion type_error integer The argument StartPosition must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer domain_error atom_length The argument StartPosition is not in the prescribed range of values type_er
594. t number of parameters Hints The information described here is formatted in accordance with the interface The appearance of the output therefore depends on the interface See also stop 4 stop_interactive 1 2 4 remove stop 0 1 activate _stop 0 1 deactivate_stop 0 1 IF Prolog V5 3 679 Reference Manual Command interface Debugger command view_variable 0 1 Display variable constraints view_variable VV view_variable VariableName vv VariableName The view_variable 1 command displays any constraints at the current breakpoint for the variable VariableName VariableName must occur in the current clause The currently valid range of values is also displayed for variables that have const_domain class constraints The view_variable 0 command can be used to display all suspended constraints at the current breakpoint Variables that do not occur in the current clause are displayed using their internal name The constraint subgoals are stored internally while the debugger is active Information on the built in predicates used to declare constraints does not exist for constraints specified before the debugger was activated In such a case the constraints are displayed in an internal format In the class const_linear inequations are transformed Expri gt Expr2 gt Expri Slack Expr2 Slack gt 0 Expri gt Expr2 gt Expri StrictSlack Expr2 StrictSlack gt 0 The so called sl
595. t options Arguments DeviceAndName Mode Options Stream Atom or structure name of the input output medium to be opened Atom read write append List of I O options Stream system defined term Reference Manual 386 IF Prolog V5 3 open 3 4 Predicate Stream processing Exceptions instantiation_error The argument DeviceAndName Mode or Options or a subterm must not be a variable but a variable was specified domain_error source_sink The value of the argument DeviceAndName is not valid for an object to be opened type_error atom The argument Mode must be an atom but is a term of another type domain_error io_mode The value of the argument Mode is invalid for the I O mode of a stream type_error list The argument Options must be a list but is a term of another type domain_error stream_option An element of Options specifies an option that is not permitted type_error variable The argument Stream must be a variable but is a term of another type permission_error open source_sink The argument DeviceAndName specifies a file or a different I O medium that cannot be opened existence_error open source_sink The argument DeviceAndName specifies a file or a different I O medium that cannot be opened for reading domain_error file_name The value of the argument DeviceAndName is not a valid name for a file permission_error open source_sink An element of Options specifies an alias that is already associate
596. t t_cursor ActGoal STRING VarName double Value The function PrologIsFloat checks if the current Prolog goal ActGoal contains a Prolog variable with the name VarName and if this variable is bound to a floating point number If such a variable is found the function stores the value of the number in Value and returns TRUE Otherwise the function returns FALSE Arguments ActGoal Structure information on the current Prolog goal VarName Character string name of a Prolog variable Value Pointer to a floating point number See also PrologIsInteger PrologIsString ProloglsTerm Reference Manual 724 IF Prolog V5 3 PrologIsInteger C Function Passive C interface Get integer from variable include cpro h BOOLEAN PrologIsInteger t_cursor ActGoal STRING VarName long Value The function PrologIsInteger checks if the current Prolog goal ActGoal contains a Prolog variable with the name VarName and if this variable is bound to an integer If such a variable is found the function stores the value of the number in Value and returns TRUE Otherwise the function returns FALSE Arguments ActGoal Structure information on the current Prolog goal VarName Character string name of a Prolog variable Value Pointer to an integer See also PrologIsFloat PrologIsString ProloglsTerm IF Prolog V5 3 725 Reference Manual Passive C interface C Function PrologIsString
597. t the time of the output and provided the special structure VAR see numbervars under write_term 2 3 was not used Example user writeq_atom a btc A lt ENTER gt A a b c lt ENTER gt Reference Manual 620 IF Prolog V5 3 writeq_atom 2 Predicate Term conversion yes user writeq_atom b 3 0 A lt ENTER gt A 2 2 ep 7572772727 3 0 lt ENTER gt yes Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also write_atom 2 writeq 1 2 write_term 2 3 parse_atom 6 stream_control 2 IF Prolog V5 3 621 Reference Manual Term conversion Predicate writeq_atom 2 Reference Manual 622 IF Prolog V5 3 Chapter 5 Overview by functionality of debugger commands This section contains an overview of the built in debugger commands arranged into groups according to their functionality The functor of each debugger command is printed in bold type This table contains only the long forms of the commands A command that is only available in the alpha surface of the debugger is identified by the character Normally these commands are not available under the command surface of the debugger stream Under the Motif surface likewise these commands are not available but it supplies graphic elements like buttons menus and scrollbars Breakpoints Comm
598. tSet C Function Active C interface Set error context include cpred h void ErrorContextSet ERRORCLASS Errorclass STRING Parm1 STRING Parm2 ARITY Argno TERM Culprit The function ErrorContextSet is used to set the error context Errorclass determines the error class Parml and Parm2 the error message Argno the argument number of the term that caused the error and Culprit the term that caused the error If the argument number of the erroneous term is not known Argno may be the value 0 If the erroneous term is not known or does not match the Argno term Culprit can be NULL Depending on Errorclass the following exceptions are created by ErrorContextSet INSTANTIATION_ERROR exception instantiation_error valid_type Parm1 argno Argno culprit Culprit goal Goal TYPE_ERROR exception type_error Parm1 Culprit argno Argno goal Goal DOMAIN_ERROR exception domain_error Parm1 Culprit argno Argno goal Goal EXISTENCE_ERROR exception existence_error Parml Culprit argno Argno goal Goal PERMISSION_ERROR exception permission_error Parml Parm2 Culprit argno Argno goal Goal REPRESENTATION_ERROR exception representation_error Parm1 Culprit argno Argno goal Goal EVALUATION_ERROR exception evaluation_error Parm1 argno Argno culprit Culprit goal Goal RESOURCE_ERROR exception resource_error Parm1 argno Argno culprit Culpr
599. tabase in the calling module or in the specified Module for clauses with a head which can be unified with Head If such a clause is found unification of Head is performed i e any variables in Head are unified with the corresponding arguments from the head of the clause found and Body is unified with the body of the clause found The first clause found is then deleted from the database The predicates retract 1 2 succeed by backtracking for all matching clauses which were found in the database at the time of the first call even if they have since been modified logic update view Arguments Clause Structure atom Head Structure atom Body Term Exceptions instantiation_error The argument Head or Clause must not be a variable but a variable was specified type_error callable The argument Head or the head of Clause must have the syntactical structure of a clause head permission_error modify static_procedure The argument Head or the head of Clause specifies an existing predicate which has not been declared as dynamic and therefore cannot be modified Hints Facts in the database have the clause body true IF Prolog V5 3 459 Reference Manual Database Predicate retract 1 2 If all clauses of a predicate are removed with retract 1 2 the predicate will remain defined but will always fail The predicate abolish 1 can be used to delete a predicate The predicate retract 1 2 is a metapredicate and manipulates the database
600. tail to form a list Last element in list Count the elements in a list Access elements of a list Concatenate atoms to form an atom Concatenate matching atoms to form an atom List membership List membership List membership Decompose a number into a list of characters Convert a list of characters into a number Decompose a number into a list of character codes Convert a list of character codes into a number Remove a sublist from a list Reverse a list Sort a list Value less than Value Value greater than Value Value less or equal Value Value greater or equal Value Value equal Value Value not equal Value Convert a number into an atom Check range Generate a sequence of integers Evaluate arithmetic expressions Query global variables Query the value of a global variable IF Prolog V5 3 23 Reference Manual Overview by functionality Predicates pop_global Name Value push_global Name Value set_global Name Value unset_global Name Stream processing assign_alias Alias Stream cancel_alias Alias close Stream close Stream Actions current_alias Alias Stream current_device_control Device Command Arity current_error Stream current_input Stream current_output Stream current_stream_control Stream Command Arity device_control Device Command Qedit Qedit Filename error_tell Stream error_telling Stream error_told file_test Pathname Ac
601. tary input output Predicate peek_char 1 2 system_error interrupted The error indicated was reported by the operating system when reading the input stream Stream type_error atom The argument Character must be a variable or an atom but is a term of another type representation_error in_character The argument Character must be a variable a character or the special atom end_ of _file but is not representable as a single character representation_error character The entity read from the stream is not representable as a single character Standard These predicates comply with the definition of the ISO standard for Prolog Compatibility V5 0B ISO conformance exception permission_error input binary_stream is gen erated instead of permission_error input text_stream when the stream is not a text stream See also get_char 1 2 peek_byte 1 2 peek_code 1 2 Reference Manual 398 IF Prolog V5 3 peek_code 1 2 Predicate Elementary input output Input a character peek_code CharCode peek_code Stream CharCode The predicate peek_code 1 peeks at the next character from the current input stream cur rent_input and unifies CharCode with its integer value The predicate peek_code 2 acts in the same way for the specified input stream Stream If the end of the input stream has been reached CharCode is unified with 1 The predicates can be applied only for text streams see open
602. ted Example user fail true lt ENTER gt no user call fail true lt ENTER gt yes Standard This language construct complies with the definition of the ISO standard for Prolog See also call 2 once 1 2 2 set_prolog_flag 2 Reference Manual 126 IF Prolog V5 3 call 2 Language construct Execution control Call a goal call Name ArgList Module The language construct cal1 2 constructs a goal from Name and ArgList Goal Name ArgList The constructed goal Goal is executed in the calling module or in the specified Module The predicate call 2 succeeds if Goal succeeds By backtracking the goal can return several results Arguments Name Atom ArgList List Exceptions instantiation_error The argument Name or List must not be a variable but a variable was specified type_error atom The argument Name must be an atom but is a term of another type type_error list The argument List must be a list but is a term of another type instantiation_error The argument Goal must not be a variable but a variable was specified type_error callable The argument Goal must have the syntactical structure of a Prolog goal existence_error procedure In executing Goal a predicate was to be activated which is not defined and the Prolog flag unknown has the value error type_error atom The argument Goal or a subgoal has been qualified by means of 2 or 2 w
603. ter are not instantiated in the call The argument is an input parameter The current parameter specified in the call must be of the prescribed type Any uninstantiated variables contained in this parameter may be instantiated in the call 37 Predicate Reference section When the argument is an atomic term there is no difference between the modes and The mode is therefore used only when the argument may be a compound term The argument is an input output parameter The current parameter must be either a variable or a term of the prescribed type In the course of the execution of the predicate this parameter is unified If this unification is not successful then the entire predicate call will fail Any uninstantiated variables contained in this parameter may be instantiated in the call The argument is a pure output parameter The current parameter must be an uninstan tiated variable If the predicate succeeds this variable is instantiated with the result of the predicate call The type of result from the predicate call is indicated in the section on Arguments in the full description Several call patterns are possible for some predicates Reference Manual 38 IF Prolog V5 3 1 0 Language construct Execution control Disable backtracking The execution of 0 cut succeeds once and once only If the cut is called as a subgoal when executing a goal G all the choice points set when executing G
604. text of the loaded module Arguments Filename Atom name of a file Exceptions instantiation_error The argument Filename must not be a variable but a variable was specified type_error atom The argument Filename must be an atom but is a term of another type domain_error file_name The value of the argument Filename is not a valid name for a file permission_error open source_sink The argument Filename specifies a file or a different I O medium that cannot be opened system_error read ea The error indicated was reported by the operating system when reading the input stream Filename domain_error save_state The argument Filename specifies a file that does not contain a system state gen erated by compile 1 save_module 1 or procmp permission_error modify static_procedure When loading the file Filename a predicate is to be defined which already exists and which may not be modified Reference Manual 328 IF Prolog V5 3 load 1 Predicate Database When initialization directives are executed init 1 or initialization 1 any excep tion may arise Hints If a module body of a module contains several init 1 or initialization 1 directives the order in which they are evaluated is undefined upon loading Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also unload 1 compile 1 save module 1 lo
605. th 0 are replaced by the atom maxdepth N Atom1 Atom2 Limits the structure depth for output to N Any subterms in a structure at a structure depth greater than N are represented by the atom Atom1 Structure levels are counted starting with 0 Lists are also structures i e N limits the length of lists as well In the case of lists all elements that follow element N in the list counting begins with 0 are replaced by the atom Atom2 quoted Bool This specification controls the behavior of write_term 2 3 for atoms which con tain special characters and for floating point numbers If Bool is true atoms are output in accordance with Prolog syntax rules For example atoms containing special characters would be quoted floating point numbers are output with the highest possible precision If Bool is false default the characters in such atoms are output without special treatment floating point numbers are output with the current floating point format see float_format 2 ignore_ops Bool This specification controls the behavior of write_term 2 3 with regard to the use of operators If Bool is true operator definitions are ignored and structures are always rep resented in normal structure notation IF Prolog V5 3 613 Reference Manual Input output for terms Predicate write_term 2 3 If Bool is false default the existing operator definitions are used to represent output portrayed Bool If Bo
606. th a special meaning A non empty list is equivalent to a normal structure of the form Head Tail where is the list functor Head indicates the first element in the list and Tail indicates the list with the remaining elements or the empty list To simplify the representation of lists Prolog provides a special list notation the elements are enclosed in square brackets separated by commas Element1 Element2 Because splitting a list into a head and a tail is a common operation a special notation has been provided for this purpose Head Tail It is also possible to enter more than one element separated by commas in front of the IF Prolog V5 3 811 Reference Manual Prolog Syntax Terms vertical bar that precedes the tail A string enclosed in double quotes is interpreted according to the value of the Prolog flag double_quotes Each occurrence of double quotes inside the string must either be entered twice or be disabled by means of a preceding backslash The following notations are therefore possible for a non empty list Head Tail Element1 f Element rea Tail Element1 Element antl chari char ua Element1 Element Head may be any terms Tail is a possibly empty list List like structures List like structures can be generated by specifying a single element instead of a tail These structures do not have all the characteristics inherent
607. the Prolog flag debug has the value on the errors encountered during reconsult 1 are collected If edit 0 1 is called again for this file a temporary file is created containing the errors dispersed in the source code The error messages are marked with gt gt gt gt at the beginning of each line If the column of the error is also known it is marked with After the temporary file has been edited to correct the errors the error information is removed and the temporary file is stored in Filename The predicates edit 0 1 do not check the existence of the file to be edited Behavior e g if the file is created then depends on the relevant editor The editor can be set with default_editor 2 The editor command is executed with sys tem 1 Most screen editors will only work well if the standard Prolog streams user_input user_ output and user_error are in fact connected to a terminal Arguments Filename Atom Exceptions instantiation_error The argument Filename must not be a variable but a variable was specified IF Prolog V5 3 223 Reference Manual Operating system Predicate edit 0 1 type_error atom The argument Filename must be an atom but is a term of another type domain_error file_name The value of the argument Filename is not a valid name for a file system_error command_failed A command passed to the operating system or a corresponding operating system function could not be executed succes
608. the alias current_output Arguments Stream Stream system defined term or alias atom Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error output stream The argument Stream is not a stream which has been opened for output open mode write or append Standard This predicate complies with the definition of the ISO standard for Prolog See also set_error 1 set input 1 current_input 1 current_output 1 current_error 1 IF Prolog V5 3 A87 Reference Manual System information Predicate set_prolog_flag 2 Set value of a Prolog flag set_prolog_flag Flag Value The predicate set_prolog_flag 2 sets the indicated Prolog Flag to Value Prolog flags are used to make global settings for IF Prolog The following table contains the available Prolog flags and their permissible values default values printed in boldface The following Prolog flags may be queried and modified Flag Value consult notify nonotify search_path Paths read_error error fail quiet report_read_error on off warning
609. the extension rational numbers rational numbers and multiple precision integers may be used The predicate number 1 succeeds for them too Example user number 353535 lt ENTER gt yes user number 4 2 lt ENTER gt yes user number 1234 0e 222 lt ENTER gt yes Standard This predicate complies with the definition of the ISO standard for Prolog See also atom 1 atomic 1 compound 1 cyclic 1 float 1 ground 1 integer 1 nonvar 1 rational 1 var 1 Reference Manual 370 IF Prolog V5 3 number _chars 2 Predicate Term conversion Convert between a number and a list of characters number_chars Number List number_chars Number List The predicate number_chars 2 establishes the relationship between a number and the list comprising of the individual characters of the number A distinction is made between two cases 1 Number is instantiated List must be either a variable or a list of variables or characters The predicate number_chars 2 creates the list of characters in Number and unifies the result with List If Number is an arithmetic expression the expression is evaluated first and the result is then converted into characters 2 Number is uninstantiated List must be a completely instantiated list of characters The predicate number_ chars 2 creates a number from List in accordance with the characters in List The result is unified with Number Arguments Nu
610. the specified Module The predicates activated in the goal must be visible in the calling module or in the specified Module unless the 2 qualification is used for such a predicate to indicate explicitly the module in which this predicate is visible The predicates activated in the goal are normally executed in the context of the module in which they are defined This does not apply to metapredicates which are executed in the context of calling module or the specified Module unless the 2 qualification is used for a metapredicate to indicate explicitly the module context in which this predicate is to be executed Example user setof X member X b a c b a L lt ENTER gt X _68 L a b c lt ENTER gt yes user setof X X 1 X 2 X 1 S lt ENTER gt X _152 S 1 2 lt ENTER gt yes user setof X Y X 1 Y 1 X 2 Y 2 X 1 Y 3 S lt ENTER gt X _152 S 1 2 lt ENTER gt yes user setof X current_op V fy X L lt ENTER gt X _68 Reference Manual 500 IF Prolog V5 3 setof 3 Predicate Execution control V 200 L lt ENTER gt X _68 V 900 L not lt ENTER gt no Standard This predicate complies with the definition of the ISO standard for Prolog See also call 1 findall 3 bagof 3 2 2 set_prolog flag 2 IF Prolog V5 3 501 Reference Manual Contexts Exceptions Predicate signal_control 2 Control signal processi
611. there is no screen connected to the current output stream or if the device driver for this output stream is not capable of executing this operation the predicate has no effect and the call succeeds nevertheless The predicate clear_screen 1 acts in the same way as clear_screen 0 but uses the screen connected to the specified output stream Stream Arguments Stream Stream system defined term or alias atom Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error output stream The argument Stream is not a stream which has been opened for output open mode write or append Hints The terminal control predicates are implemented via the appropriate stream control functions of the device drivers see stream_control 2 The standard device drivers implement screen control via the terminfo termcap ser vice of the operating system They support only one terminal type for all output streams Reference Manual 148 IF Prolog V5 3 clear_screen 0 1 Predicate Screen control Standard These predicates are not required by the ISO standa
612. they are not available in ISO compatibility mode see Prolog flag iso Reference Manual 418 IF Prolog V5 3 profile_stat 0 1 Predicate Profiling Compatibility V5 1A The predicates profile_stat 0 1 are new See also profile 1 2 profile_reset 0 trace 1 trace_output 4 trace_config 3 debug 1 call 1 set_prolog_flag 2 import 1 IF Prolog V5 3 419 Reference Manual Execution control User definable predicate program 0 Automatically call a Prolog goal program Body The predicate program 0 in the module user is not a built in predicate but one which can be defined by the user It is used to ensure that a Prolog application runs automatically If after IF Prolog has been started and the system parameters have been processed i e when all load and consult requests given on the command line have been executed the predicate program 0 is visible in the module user then this predicate is called instead of starting the Prolog input loop break 0 Once it has been executed IF Prolog is exited Hints Any application that is activated by program 0 must be fully and independently re sponsible for error handling Since the context which is otherwise defined in the Prolog input loop to trap all exceptions is not active at the time program 0 is initiated any exception that occurs when executing program 0 will result in the termination of the program unless such exceptions are handled or trapped in the
613. tialization Configure the tracer User defined termination of the tracer User defined output predicate for the tracer Reference Manual 32 IF Prolog V5 3 Predicates Overview by functionality Memory management current_memory_ management Area Parameter Value garbage_collection Area set_memory_management Area Parameter Value statistics statistics Type ResultList System information current_prolog_flag Flag Value help help Pattern manual manual Functor manual Predicate program_parameters ParameterList prolog_serial Serial prolog_version Version proroot Path set_prolog_flag Flag Value set_prolog_flag Flag Value system _hostid Hostid system_name SystemName system_parameters ParameterList user_parameters ParameterList Operating system environment chdir Dir default _editor EditorOld EditorNew Qedit edit Filename exec Command exec Prog Args Query memory management parameters Activate garbage collection Set memory management parameters Print system values Query system values Query Prolog flags Display information about help Display help information Output manual pages Output manual pages Output manual pages Query parameters from IF Prolog call Query IF Prolog serial number Query IF Prolog version Query path of IF Prolog system Set value of a Prolog flag Set value of a Prolog flag directive
614. tion 100 xfx Module specification 50 xfx Definition module of the predicate IF Prolog V5 3 819 Reference Manual Prolog Syntax Arithmetic expressions and functions Some of the operators in this table have special meanings when the Prolog system is reading in clauses The remaining operators are functors of predicates and arithmetic functions 9 3 3 Test and definition predicates Predicate Task op 3 Define or delete operators current_op 3 Query information about operator definitions Operators are declared with op Precedence Type Names op 3 can be used as a pre dicate or as a directive An existing operator definition is overwritten by a new operator definition If 0 is specified as the precedence an existing operator definition is deleted 9 4 Arithmetic expressions and functions An arithmetic expression is a structure whose functors are all arithmetic functions The arguments of these functions are numbers arithmetic functions or arithmetic expressions Examples N 1 2 2 x K 33 9 time 1000 These expressions are evaluated in the following cases e if the expression occurs as the second argument of is X is arithmetic_expression e if arguments in a Prolog predicate are evaluated implicitly e g the comparison pred icates for numeric values The evaluation sequence is determined by the type and precedence of the operators involved and by any explicit parentheses The order of evaluation confor
615. tion_error The argument Stream or Position must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream domain_error stream_position The argument Position is not a position specification permitted for setting the I O stream as supplied by stream_property 2 permission_error reposition stream The argument Stream is an I O stream which does not permit positioning Hints Positioning is realized by corresponding stream control functions of the device drivers see stream_control 2 IF Prolog V5 3 497 Reference Manual Stream processing Predicate set_stream_position 2 Standard This predicate complies with the definition of the ISO standard for Prolog See also open 3 4 stream_property 2 Reference Manual 498 IF Prolog V5 3 setof 3 Predicate Execution control Find selected solutions of a goal setof Term Goal TermList Module The predicate setof 3 unifies TermList with a sorted and duplicate free list see sort 2 of all instantiations of Term with which Goal succeeds Term and Goal should share common variables Backtracking can take place by the variab
616. tion_error underflow An arithmetic underflow was detected during the evaluation of Expression evaluation_error undefined An arithmetic function with invalid arguments was called during the evaluation of Expression evaluation_error zero_divisor Division by 0 was performed during the evaluation of Expression Hints The atom is is defined as an infix operator IF Prolog V5 3 313 Reference Manual Arithmetic Predicate is 2 During compilation assert or compile 1 of a predicate containing is 2 the arithmetic expressions can be checked and optimized if possible Rational numbers big integers and the operator rdiv 2 can only be used when con figured Rational numbers can only be used in operations which are suitable for the Q Operand Example Use of operator notation in simple arithmetic expressions user X is 47 11 lt ENTER gt X 58 lt ENTER gt yes user A 6 X is 3 4 12 A lt ENTER gt A 6 X 79 lt ENTER gt yes Use of structure notation in simple arithmetic expressions user is X 47 11 lt ENTER gt X 58 lt ENTER gt yes Use of standard arithmetic functions in arithmetic expressions user X is abs cos sqrt pi lt ENTER gt X 0 200294 lt ENTER gt yes Use of zero arity functions in arithmetic expressions user DF is dsize 100 dused 100 lt ENTER gt DF 245141 lt ENTER gt yes Reference Manual 314 IF Prolog
617. tive 1 2 4 Set explicit breakpoint system 0 Interrupt interactive debugger and start the shell trace 0 1 Logging passes through ports trace ports set Tace DONS oe eres he Se eee Ce ESS unify Umiy Vara Dle c e bo eee Hed wae wee we ea ee eS View lt f 0 Select display fields so sose sr pa eeb ea dee em es view_ancestors 0 1 Show dynamic call chain view_configuration 0 Display default values view constraints 0 Display constraints lt o sos s 4 644 24 6b sees aS view_module 0 1 Display list of predicates in module view_predicate 0 1 Display listing of a predicate view_ _screen 0 Display history view_stops 0 Display explicit breakpoints view_variable 0 1 Display variable constraints 7 Overview by functionality of C interface xiv 8 Reference section on C functions 691 Choot Link a C function to IF Prolog 2s44 444 544 4 444 692 CPRED Add a complex C function to IF Prolog 693 CPRIM Add a simple C function toIF Prolog 694 Cshutdown Call a C function on IF Prolog shutdown 695 DeviceCreate Register device driver 2 204 696 EndProlog Release memory space used by IF Prolog 697 ErrorContextClear Clear error context
618. to be used for displaying terms Atoms have a structure depth of 0 If terms have a greater nesting depth the terms of the last display depth are displayed with the format Functor or in lists There is no restriction if 0 is specified Arguments Depth Integer or integer expression Depth gt 0 Exceptions instantiation_error The argument Depth or a subterm must not be a variable but a variable was specified type_error integer The argument Depth must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer domain_error not_less_than_zero The argument Depth must be a positive integer but is negative domain_error arity The command set_debug_depth 1 was called with an incorrect number of param eters Furthermore if an arithmetic expression is specified for the argument Depth all the exceptions for is 2 can occur See also set_trace_depth 1 IF Prolog V5 3 653 Reference Manual Alpha interface Alpha interface set_history 1 Configure history set_history Number sh Number The set_history 1 command is used to specify the number of goal and clause boxes to be stored The goal and clause boxes at the interactive breakpoints are stored in chronological order Arguments Number Integer or integer expression number of boxes to be stored Exceptions instantiation_error The argument Number
619. to system 3 except that the standard error output can also be set for command execution and Pid is unified with the process ID number of the generated child process Arguments Command Atom Input Stream system defined term or alias atom Output Stream system defined term or alias atom Error Stream system defined term or alias atom Pid Integer Exceptions instantiation_error The argument Command must not be a variable but a variable was specified type_error atom The argument Command must be an atom but is a term of another type system_error fork_failed No new process could be created This is often due to resource bottlenecks or limitations in the operating system Reference Manual 554 IF Prolog V5 3 system 3 5 Predicate Operating system system_error exec_failed The command Command could not be started Possibly this is because the com mand could not be found in the current environment domain_error stream_or_alias The argument Input Output or Error must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Input Output or Error must be associated with an open input output stream permission_error input stream The argument Input is not a variable or a stream which has been opened for input open mode read permission_error output s
620. tom Exceptions instantiation_error The argument Stream or Number must not be a variable but a variable was specified type_error integer The argument Number must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error output stream The argument Stream is not a stream which has been opened for output open mode write or append system_error write system_error close system_error flush_output system_error interrupted The indicated error was reported by the operating system when writing on the output stream Stream Furthermore if an arithmetic expression is specified for the argument Number all the exceptions for is 2 can occur IF Prolog V5 3 563 Reference Manual Elementary input output Predicate tab 1 2 Hints The predicate tab 1 2 positions the cursor relative to its current position outtab 1 2 positions it absolutely Example user write Test tab 5 lt ENTER gt write Prolog nl lt ENTER gt Test Prolog yes user write not tab 5 lt EN
621. tor Arity Functor Atom Arity Integer 0 lt Arity lt 127 Exceptions Errors in directives are detected with consult 1 reconsult 1 or compile 1 No exceptions are generated Instead only error messages are output on the current error output stream This directive can produce the following error messages instantiation_error The argument PredicateList or a subterm must not be a variable but a variable was specified type_error list The argument PredicateList must be a regular list but is a term of another type or not regular type_error predicate_indicator The argument Predicate in PredicateList must be a predicate indicator i e a structure with the format Functor Arity but is a term of another type type_error atom The name of the predicate Predicate in PredicateList must be an atom IF Prolog V5 3 413 Reference Manual Module concept Directive private 1 type_error integer The arity of the predicate Predicate in PredicateList must be an integer domain_error not_less_then_zero The arity of the predicate Predicate in PredicateList must be a positive integer but is negative representation_error max_arity The arity of the predicate Predicate in PredicateList must be an integer in the range 0 127 but is larger permission_error modify procedure The predicate indicator Predicate in PredicateList specifies a predicate which al ready exists and is not modifiable or which is the name of a language co
622. tput stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream instantiation_error The argument Command or a subterm must not be a variable but a variable was specified type_error atom_or_compound The argument Command must be an atom or a structure but is a term of another type domain_error stream_control The value of the argument Command is not any of the values permitted for a command for I O stream control IF Prolog V5 3 533 Reference Manual Stream processing Predicate stream_control 2 Hints The command get_last 2 is not supported by any of the built in device drivers if it is implemented in an additionally linked in device driver the predicate get_last 2 3 can use this capability Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also current_stream_control 3 stream_device 2 Reference Manual 534 IF Prolog V5 3 stream_copy 2 Predicate Stream processing Redefine streams stream_copy Stream1 Stream2 The predicate stream_copy 2 is primarily used to make a specified input output stream to a standard stream during a IF Prolog process For example if Stream2 has the value u
623. tream The argument Output or Error is not a variable or a stream which has been opened for output open mode write or append permission_error duplicate stream The argument Input Output or Error specifies an input output stream that is not suitable for the required operation type_error integer The argument Pid must be a variable or an integer but is a term of another type Hints These predicates are system dependent and may not be available on all operating sys tems Command is executed with exec 1 in a separate process The completion of the command to be executed is awaited only if Input is associated with a terminal otherwise execution takes place asynchronously with the IF Prolog process Extreme caution is required in connection with signals For example if a command which reads from user_input a terminal and ignores the signal interrupt is executed with system 3 the arrival of this signal may cause system 3 to abort with an exception while the command continues to exist as an independent process The IF Prolog system would return to the input loop break O and wait for input from the user but so would the command so both processes would end up competing for the user input Example The following example shows how output from a command is redirected to a file IF Prolog V5 3 555 Reference Manual Operating system Predicate system 3 5 user open example write Stream lt ENTER gt system 1s 1
624. tructure Arity Integer 0 lt Arity lt 127 Args Vector consisting of term variables Exceptions instantiation_error The argument Term or a subterm must not be a variable but a variable was specified type_error atom_or_compound The argument Term must be an atom or a structure but is a term of another type domain_error compound The argument Term is a structure but its functor or arity are not correct The following error causes IF Prolog to be exited implementation_error Arity arity out of range The argument Arity is not within the range 0 127 Example The following simple C function realizes a predicate indicator 1 which checks if its argument is a predicate indicator and returns name and arity IF Prolog V5 3 761 Reference Manual Active C interface C Function TermlsUniversal include cpred h BOOLEAN indicator_3 void xx indicator Term Name Arity TERM args 2 long number STRING string return TermIsUniversal PrologArg 1 2 args amp amp TermIsAtom args 0 amp string amp amp TermIsInteger args 1 number amp amp TermUnify PrologArg 2 args 0 amp amp TermUnify PrologArg 3 args 1 void Cboot void CPRIM indicator 3 indicator_3 See also TermIsCompound TermIsFunctor TermMakeUniversal Reference Manual 762 IF Prolog V5 3 TermIsVar C Function Active C interface Test for variable include cpred h
625. ty mode see Prolog flag iso See also clause 2 asserta_with names 2 3 assertz_with names 2 3 listing 0 1 IF Prolog V5 3 143 Reference Manual Screen control Predicate clear_eol 0 1 Clear to end of line clear_eol clear_eol Stream The predicate clear_eol 0 clears the remainder of the line on the screen connected to the current output stream starting at the cursor position The position where the cursor is currently located is also cleared If there is no screen connected to the current output stream or if the device driver for this output stream is not capable of executing this operation the predicate has no effect and the call succeeds nevertheless The predicate clear_eol 1 acts in the same way as clear_eol 0O but uses the screen connected to the specified output stream Stream Arguments Stream Stream system defined term or alias atom Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error output stream The argument Stream is not a stream which has been opened for output open mode wr
626. ty of predicates and structures min_integer The value indicates the smallest representable machine precision 32 or 64 bit integer max_integer The value indicates the largest representable machine precision 32 or 64 bit integer bounded This flag can assume the following values true Integer arithmetic returns correct values only if the operands and the mathematically correct re sult lie within the closed interval min_integer max_integer false Integer arithmetic always returns correct results or an exception is created if this is not possible integer_rounding_function This flag can assume the following values down The arithmetic functions and rem round their re sult down if necessary toward_zero The arithmetic functions and rem round the ab solute value of their result down if necessary float_min The value indicates the smallest representable floating point number float_max The value indicates the largest representable floating point number The predicate current_prolog_flag 2 succeeds by backtracking for all the Prolog flags and values which were set at the time of the first call even if they have since been modified logic update view Arguments Flag Atom Value Term Exceptions type_error atom The argument Flag must be a variable or an atom but is a term of another type Reference Manual 194 IF Prolog V5 3 current _prolog_flag 2 Predicate System information domain_error prolog_flag T
627. ue lt ENTER gt yes Standard This language construct complies with the definition of the ISO standard for Prolog See also 2 call 1 2 2 set_prolog_flag 2 IF Prolog V5 3 43 Reference Manual Database Language construct gt 2 Create a grammar rule Arg1 gt Arg2 gt Argl Arg2 The atom gt does not denote a built in predicate but is a built in operator which is inter preted in a special way by consult 1 reconsult 1 and compile 1 Clauses formulated as shown above are converted into normal Prolog rules when they are read in with consult 1 reconsult 1 or compile 1 These Prolog rules are normally used for parsing lists of terms characters in mosts cases This mechanism can be used to parse natural language or to define sentences of a formal language The operator notation with gt illustrates the constituent structure The higher level con stituent which is always non terminal is on the left of the arrow One or more terminal and or non terminal constituents are specified to the right of the arrow The conversion mechanism for gt ensures that both Arg and Arg2 are supplied with additional arguments A method called the differential list method is used The first argument added by the mechanism is a list which starts with the string of terms to be parsed The second argument is a list containing the remainder of the first list without the first part which
628. ues TERM_VAR The term is an uninstantiated Prolog variable TERM_ATOM The term is a Prolog atom TERM_INTEGER The term is an integer within the range of values for a C variable of the type signed long TERM_FLOAT The term is a floating point number TERM_COMPOUND The term is a structure TERM_OTHER The term has a type not listed above Arguments Term Term variable Hints Future versions of IF Prolog will extend the definition of the data type TERMTYPE If the TermType function is used the user should make sure that the function can also return a value that is not currently defined as the result Example The following simple C function realizes a predicate type_of 2 which gives the type to a given term Reference Manual 778 IF Prolog V5 3 TermType C Function Active C interface include cpred h BOOLEAN type_of_2 void k type_of Term Type STRING typename switch TermType PrologArg 1 case TERM_VAR typename var break case TERM_INTEGER typename integer break case TERM_FLOAT typename float break case TERM_ATOM typename atom break case TERM_COMPOUND typename compound break default typename unknown return TermUnifyAtom PrologArg 2 typename void Cboot void T CPRIM type_of 2 type_of_2 See also TermDecompose IF Prolog V5 3 779 Reference Manual Active C interface C Function Term Unif
629. uilt in predicates is supplied in this file Its structure is described in the beginning of the file The environment variable PROHELP may contain several filenames separated by the char acter The files will be searched in the given order This enables the user to add own help files to the system IF Prolog V5 3 291 Reference Manual System information Predicate help 0 1 Example user help lt ENTER gt help Pattern help The predicate help 1 displays suitable help information for the specified Pattern if such information is available The argument Pattern can be specified as for match 2 3 and in most cases will be the name of a predicate Search for help information takes place in the files defined by the environment variable PROHELP If this variable does not exist the file prolib system hlp under the IF Prolog root directory see proroot 1 will be used Help information on all the built in predicates is supplied in this file Its structure is described in the beginning of the file The environment variable PROHELP may contain several filenames separated by the character The files will be searched in the given order This enables the user to add own help files to the system help Pattern yes System predicates Display help information user help abo lt ENTER gt abolish Predicate Module abort yes Standard Sy
630. ule yes With global variables you can exchange information between different predicates without having to pass this information using explicitly specified arguments IF Prolog V5 3 807 Reference Manual Prolog Syntax Terms Stacks of global variables A stack of values can be administered under the name of a global variable The following rules apply e set_global 2 creates a stack with precisely one entry and at the same time any existing stack for the same variable is deleted e push_global 2 adds a further entry to an existing stack as the top element If the global variable does not yet exist a stack with one entry is created e get_global 2 is used to query the value of the top element If the global variable does not exist the Prolog system reports an error e pop_global 2 is used to query the value of the top element The top value is then removed from the stack When the last entry in the stack is removed the global variable is also deleted If the global variable does not exist the Prolog system reports an error e unset_global 1 removes the entire stack and the global variable Example of global variables user set_global glob 1 get_global glob Prot write Proi nl set_global glob nun get_global glob Pro2 write Pro2 nl write glob 1 nun glob Prol Pro2 m nun yes In this example the global variable glob is assigned a value more than once during goal execution and the
631. ule interface and a module body which are interlinked by a common module name Private portion of the module introduced by the begin_module directive and containing a declaration part and an implementa tion part Public portion of the module introduced by the module directive Atom which may occur as a functor in prefix infix or postfix notation The notation of the operator is determined by the predicate or the directive op 3 An operator has an precedence and an associativity which make it possible to determine which arguments and terms of different or matching precedence can be assigned to one another A calculated value is greater than the storage location provided for it Component of the Prolog system which converts character strings into Prolog terms Structure notation where the operator follows the operands e g A B A relation identified by functor and arity Structure notation where the operator precedes the operands e g A B A compound term Functor Arity Outermost functor in term notation An empty or non empty sequence of clauses in a database defin ing a predicate System state which can be queried and in some cases set by the user A sequence of terms representing clauses and directives Sequence of logical conclusions which produce a statement from facts The paths taken by the system during proving of a goal can be mapped onto a tree structure both the successful paths and also the blind alleys a
632. ule is first deleted The interface cannot be redefined for the built in module user The interface of a module may only contain the directives permitted there namely char_ conversion 2 export 1 reexport 1 2 meta 1 op 3 or include 1 Arguments Module Atom Exceptions Errors in directives are detected with consult 1 reconsult 1 or compile 1 No exceptions are generated Instead only error messages are output on the current error output stream This directive can produce the following error messages instantiation_error The argument Module must not be a variable but a variable was specified type_error atom The argument Module must be an atom but is a term of another type permission_error modify system_module The argument Module is the name of a system module System modules may not be modified permission_error modify module The argument Module is the name of a module with an interface which cannot be modified e g user Hints The atom module is defined as a prefix operator Directives are evaluated during consultation see consult 1 reconsult 1 or compi lation see compile 1 procmp command Reference Manual 354 IF Prolog V5 3 module 1 Directive Module concept Standard The directive module 1 is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also begin_module 1 end_module 0 1 export 1 meta 1 import 1
633. umber Garbage Time Number is the number of garbage collection calls for the associated memory area Garbage is the amount of memory released in bytes and Time is the CPU time used for IF Prolog V5 3 529 Reference Manual Memory management Predicate statistics 0 2 the garbage collection in seconds No values are made available for the stack constraints since the garbage collection of this stack is performed together with the garbage collection of the global stack Accounting relating to the garbage collection for the constraint stack is included in the information for the global stack Arguments Type Atom time memory garbage_collection Result List List with the format Name Value Name Term Value Term Exceptions type_error atom The argument Type must be a variable or an atom but is a term of another type type_error list The argument ResultList must be a variable or a list but is a term of another type Example Query system values user statistics lt ENTER gt memory statistic size used gc collected gc time database 700404 461648 1 1384 0 00 global 30720 412 0 0 0 00 constraints 8192 0 local 30720 396 0 0 0 00 extension 8192 0 0 0 0 00 trail 8192 20 0 0 0 00 total 786420 462476 1 1384 0 00 date Thu Jul 14 15 08 36 1994 cputime 1 63 yes Query used time Reference Manual 530 IF Prolog V5 3 statistics 0 2 Predicate Memory management user
634. umber 1 a number integer 1 an integer number float 1 a floating point number rational 1 a rational number extension var 1 an uninstantiated variable nonvar 1 not an uninstantiated variable compound 1 a structure Reference Manual 798 IF Prolog V5 3 Terms Prolog Syntax When a term is read any superfluous parentheses are ignored so the query user atomic a yes succeeds because a is an atom 9 2 1 Constants In Prolog there are two different kinds of constants e atoms e numbers Atoms Atoms are defined as follows e character strings consisting of letters digits and underscore characters and beginning with a lowercase letter e any character strings enclosed in single quotes Even the empty character string two single quotes is an atom Each single quote within an atom must be represented by two single quotes or be disabled by means of a preceding backslash e character strings made up of special characters e the empty list represented by a pair of square brackets is also interpreted as an atom Special requirements for entering atoms The backslash has a special meaning when appearing in atoms the atoms must then be enclosed in single quotes e If the backslash is followed by one of the following letters this combination is inter preted as a control character IF Prolog V5 3 799 Reference Manual Prolog Syntax Terms String ASCII d
635. ument ClauseNumber must be an integer greater than zero but is negative or equal to zero existence_error clause_number The argument ClauseNumber does not specify an existing clause type_error atom_or_list The argument Ports must be an atom or a list of atoms but is a term of another type domain_error port The argument Ports is not valid for a port of the box model type_error atom The argument BindingType must be an atom but is a term of another type domain_error binding The value of the argument BindingType is invalid for the binding of a variable domain_error condition The value of the argument Conditions is an invalid condition for a breakpoint domain_error match The argument Conditions contains a match condition that is not compatible with the specified predicate Reference Manual 664 IF Prolog V5 3 stop 4 stop_interactive 1 2 4 Debugger command Command interface existence_error command The argument Actions contains a command that is unknown to the debugger permission_error apply command The argument Actions contains a command that is not permitted at a breakpoint type_error integer _or_variable The argument SubGoalNumber Variable must be an integer or a variable but is a term of another type domain_error arity The command stop 4 or stop_interactive 1 2 4 was called with an incorrect number of parameters Hints No breakpoint can be set at language constructs such as gt The b
636. ument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error output stream The argument Stream is not a stream which has been opened for output open mode write or append system_error write system_error close system_error flush_output system_error interrupted The indicated error was reported by the operating system when writing on the output stream Stream Hints The way in which an input output stream is buffered can be defined when it is opened see open 4 Reference Manual 256 IF Prolog V5 3 flush_output 0 1 Predicate File processing Standard These predicates comply with the definition of the ISO standard for Prolog IF Prolog V5 3 257 Reference Manual Arithmetic Predicate for 3 Generate a sequence of integers for Start Counter End for Start Counter End The predicate for 3 generates a sequence of integers in ascending or descending order or checks whether an integer lies within a specified range If Counter is not instantiated then it is unified by backtracking first with Start then with all integers betwe
637. ument with a precedence less than that of f is allowed to occur and y indicates the position where the precedence of the argument must be less than or equal to that of f Notation operator Type fx prefix operator fy prefix operator xf postfix operator yf postfix operator xfx infix operator xfy infix operator yfx infix operator Precedence x lt Precedence f Precedence y lt Precedence f Operators declared with fy or xfy are called right associative and those declared with yf or yfx are called left associative see 11 To avoid ambiguity when converting parenthesized expressions with two or more operators the operators you define yourself should either be assigned different precedence numbers or be declared with identical argument precedence attributes if the operator precedence is identical i e operators with identical precedence should be either all left associative or all right associative Ambiguities may arise if you fail to do this Examples of left and right associative operators user op 500 xfy plus vight associative yes user op 500 yfx minus left associative yes user write_term 1 plus 2 plus 3 ignore_ops true plus 1 plus 2 3 yes user write_term 1 minus 2 minus 3 ignore_ops true IF Prolog V5 3 815 Reference Manual Prolog Syntax Operators minus minus 1 2 3 yes Converting expressions with two or more operators into normal structures
638. us_clause The command back_clause 0 cannot be executed at this point in the proof tree because the current breakpoint is already located at the first clause of the current predicate domain_error arity The command back_clause 0 was called with an incorrect number of parameters See also back_subgoal 0 back_parent 0 Reference Manual 634 IF Prolog V5 3 back_parent 0 Debugger command Command interface Branch back to CALL port of parent goal back_parent bp The back_parent 0 is used to branch back to the CALL port of the parent goal in the proof tree and stop there Because execution of this command is equivalent to resetting the system to a previous state variable instantiations may be undone If no parent goal exists the debugger reports an error Exceptions existence_error parent The command back_parent 0 cannot be executed at this point in the proof tree domain_error arity The command back_parent 0 was called with an incorrect number of parameters See also back_subgoal 0 back_clause 0 IF Prolog V5 3 635 Reference Manual Command interface Debugger command back_subgoal 0 Branch back to CALL port of subgoal back_subgoal b The back_subgoal 0 command is used to branch back to the CALL or WAKEUP port of the current subgoal If the command is entered at a CALL or WAKEUP port the debugger branches back to the CALL or WAKEUP port of the ancestor goal The debugger sto
639. used for a meta predicate to indicate explicitly the module context in which this predicate is to be executed Reference Manual 48 IF Prolog V5 3 gt 2 Language construct Execution control Example Using the IF THEN construct the predicate append_x 3 see 0 can be defined with only one clause and without a cut user listing lt ENTER gt h user append_x 3 x x append_x L1 L2 L3 Li gt L2 L3 Li XIT1 L3 XIT3 append_x T1 L2 T3 yes user append_x a b c L lt ENTER gt L a b c lt ENTER gt yes user append_x X Y a b lt ENTER gt X Y a b lt ENTER gt no Standard This language construct complies with the definition of the ISO standard for Prolog See also 2 0 if 3 call 1 2 2 set prolog flag 2 IF Prolog V5 3 49 Reference Manual Database Predicate J2 List notation for consult 1 reconsult 1 Filename Module Filename Module Filename Filelist Module Filename Filelist Module The predicate 2 is functionally identical to consult 1 and reconsult 1 It is simply an abbreviated notation particularly if a number of files are to be consulted or reconsulted If an element of the list has the form Filename then reconsult 1 is called for this Filename otherwise consult 1 Elements are processed one by one
640. ush its output buffer The argument Stream identifies the input output stream and has been given to the control function as argument The integer pointed at by Number is set to the number of characters which were in the buffer prior to flushing If the constant NULL has been passed for the argument Number the argument is not set Arguments Stream Stream Number Pointer to long Hints The data structures and functions of device drivers are described in the F Prolog User s Guide 2 See also DeviceCreate flush_output 0 1 Reference Manual 736 IF Prolog V5 3 StreamMode C Function Device driver interface Query stream mode include device h t_iomode StreamMode t_stream Stream The function StreamMode returns the mode of a stream The argument Stream identifies the input output stream and has been given to the control function as argument By means of this function the device driver does not necessarily have to store all the mode information of every opened stream Arguments Stream Stream Hints The data structures and functions of device drivers are described in the IF Prolog User s Guide 2 See also DeviceCreate stream_property 2 IF Prolog V5 3 737 Reference Manual Active C interface C Function TermAddList Add to a Prolog list include cpred h BOOLEAN TermAddList TERM Tail TERM Term The function TermAddList is used to
641. ust be a variable or a structure of the form Host Port but is a term of another type IF Prolog V5 3 511 Reference Manual Net communication Predicate socket_accept 3 type_error atom The argument Host must be a variable or an atom but is a term of another type type_error integer The argument Port must be a variable or an integer but is a term of another type type_error atom The argument Filename must be a variable or an atom but is a term of another type type_error variable The argument NewSocket must be a variable but is a term of another type system_error too_many_sockets The system imposed limit for the number of sockets has been exceeded Hints This predicate is used only in a server process The client process uses the predicate socket_connect 2 Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso See also socket 3 current socket 3 alarm 1 host addr 2 socket_bind 2 socket_close 1 socket_connect 2 socket_listen 1 2 socket_receive 2 3 socket_raw_receive 4 5 socket_send 2 3 socket_shutdown 1 2 Reference Manual 512 IF Prolog V5 3 socket_bind 2 Predicate Net communication Bind a name to a socket socket_bind Socket Addr The predicate socket_bind 2 assigns a name to the socket Socket The argument Addr specifies the name to which the socket is to be assigned
642. ut stream Stream is positioned at the end of a line An input stream is positioned at the end of an input line if a subsequent character read operation would yield the new line character n or if the end of the input stream would be reached Arguments Stream Stream system defined term or alias atom Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream permission_error input stream The argument Stream is not a stream which has been opened for input open mode read system_error read ee E The error indicated was reported by the operating system when reading the input stream Stream existence_error stream The argument Stream must be associated with an open input output stream Hints The predicates at_end_of_line 0 1 must inspect the next character in the input stream It is therefore possible that the system will have to wait for an input IF Prolog V5 3 93 Reference Manual Elementary input output Predicate at_end_of_line 0 1 Example The following predicate skips the rest of an input line including the terminating new line character user listing lt ENTER gt h user skip_comment 0 x skip_comment
643. uting ConditionGoal ThenGoal or ElseGoal a predicate was to be activated which is not defined and the Prolog flag unknown has the value error type_error atom The argument ConditionGoal ThenGoal or ElseGoal or a subgoal has been qual ified by means of 2 or 2 with a term that is not an atom existence_error module The argument ConditionGoal ThenGoal or ElseGoal or a subgoal is qualified by means of 2 or 2 with an atom that does not name an existing module Hints Using this language construct enables you to avoid many applications of cut 0 The call ConditionGoal gt ThenGoal is equivalent to ConditionGoal gt ThenGoal fail The atom gt is defined as an infix operator The language construct gt 2 is not a predicate so it cannot be redefined The pred icates current_predicate 1 and current_visible 2 do not indicate language con structs Explicit module qualification with 2 or 2 is not permitted for language constructs with the exception of ca11 1 The predicates activated in the goal must be visible in the specified Module unless the 2 qualification is used for such a predicate to indicate explicitly the module in which this predicate is visible The predicates activated in the goal are normally executed in the context of the module in which they are defined This does not apply to metapredicates which are executed in the context of the specified Module unless the 2 qualification is
644. utput stream Stream Arguments Stream Stream system defined term or alias atom Line Integer Column Integer Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error output stream The argument Stream is not a stream which has been opened for output open mode write or append type_error integer The argument Line or Column must be a variable or an integer but is a term of another type IF Prolog V5 3 277 Reference Manual Screen control Predicate get_last 2 3 Hints The terminal control predicates are implemented via the appropriate stream control functions of the device drivers see stream_control 2 The standard device drivers implement screen control via the terminfo termcap ser vice of the operating system They support only one terminal type for all output streams The standard device drivers see stream_control 2 do not support true position queries instead they always supply the position set by move_cursor 2 3 Standard These predicates are not required by the ISO standard for Prolog Therefore they are
645. variable was specified type_error integer The argument Number must be an integer or an integer expression but is a term of another type or the result of the evaluation of the expression is not an integer domain_error not_less_than_zero The argument Number must be a positive integer but is negative domain_error arity The command fast_skip 0 1 was called with an incorrect number of parameters Furthermore if an arithmetic expression is specified for the argument Number all the exceptions for is 2 can occur See also step 0 continue 0 nonstop 0 skip 0 1 IF Prolog V5 3 645 Reference Manual Command interface Debugger command halt 0 Terminate debugger and IF Prolog halt H The halt 0 command aborts the debugger and terminates IF Prolog The command is equivalent to call halt Exceptions domain_error arity The command halt 0 was called with an incorrect number of parameters See also call 1 break 0 abort 0 predicate halt 0 Reference Manual 646 IF Prolog V5 3 help 0 Debugger command Command interface Display help information help h This command displays a list of commands with a brief description of each as help informa tion Exceptions domain_error arity The command help 0 was called with an incorrect number of parameters Hints The information described here is formatted and supplemented in accordance with the interface The appearance of the output ther
646. vices or etc inet services Arguments Service Atom Protocol Atom tcp udp Port Integer Exceptions instantiation_error The argument Service must not be a variable but a variable was specified type_error atom The argument Service must be an atom but is a term of another type domain_error service The argument Service does not specify an existing TCP IP service type_error atom The argument Protocol must be a variable or an atom but is a term of another type domain_error protocol The argument Protocol does not specify a valid TCP IP protocol type_error integer The argument Port must be a variable or an integer but is a term of another type Standard This predicate is not required by the ISO standard for Prolog Therefore it is not available in ISO compatibility mode see Prolog flag iso Reference Manual 360 IF Prolog V5 3 net_service 3 Predicate Net communication See also current_host 1 host_addr 2 socket 3 IF Prolog V5 3 361 Reference Manual Elementary input output Predicate nl 0 1 Output newline nl nl Stream The predicate n1 0 outputs the new line character on the current output stream current_ output The predicate n1 1 has the same effect but on the specified output stream Stream Arguments Stream Stream system defined term or alias atom Exceptions instantiation_error The argument Stream must not be a variable but a variable was
647. writes to the specified output stream Stream Both predicates output atoms with special characters in accordance with Prolog syntax so these atoms can be read in again Floating point numbers are output wich maximum precision Arguments Term Term Stream Stream system defined term or alias atom Exceptions instantiation_error The argument Stream must not be a variable but a variable was specified domain_error stream_or_alias The argument Stream must be an input output stream supplied by open 3 4 or an atom which has been registered with assign_alias 2 or with the alias option for open 4 as an alias for an input output stream existence_error stream The argument Stream must be associated with an open input output stream permission_error output stream The argument Stream is not a stream which has been opened for output open mode write or append system_error write system_error close system_error flush_output system_error interrupted The indicated error was reported by the operating system when writing on the output stream Stream Reference Manual 618 IF Prolog V5 3 writeq 1 2 Predicate Input output for terms Hints The call writeq Term is identical to write_term Term quoted true numbervars true The output produced by writeq 1 2 is generally suitable for re input e g with read_ term 2 3 provided the same operator definitions are used for input as at the time of the output and prov
648. written without parentheses For structures with an arity of one or two an alternative notation may be used if the functor has been defined as a prefix infix or postfix operator Term whose proof must succeed in order that the given goal may be proved One of the objects variable number atom or structure Memory area in the Prolog system for temporary storage of vari able instantiations Predicate which must be defined by the user Method for making two terms identical through the substitution of variables Reference Manual 834 IF Prolog V5 3 Bibliography 10 11 12 13 14 IF Prolog V5 3 Reference Manual IF Prolog V5 3 User s Guide IF Prolog V5 3 OSF Motif Interface IF Prolog V5 3 Informix Interface IF Prolog V5 3 Constraints Package IF Prolog V5 3 Quick Reference IF Prolog V5 3 Windows Interfaces IF Prolog V5 3 Java Interface IF Prolog V5 3 BDD Package X Open CAE Common Applications Environment Specification System Interfaces and Headers Issue 4 Prentice Hall 1994 International Standard ISO IEC IS 13211 1 International Organization for Standard ization 1995 William F Clocksin Chris S Mellish Programming in PROLOG Standard Edition Berlin et al Springer 1995 Ivan Bratko PROLOG Programming for Artificial Intelligence Second Edition Addison Wesley 1990 Leon Sterling Ehud Shapiro The Art of PROLOG Advanced Programming Tech niques Cambridge
649. x link to IF Prolog 692 C predicates argument access 716 call grammar rules 401 call a goal automatically 420 CALL port 635 636 ceiling 309 character access in atom 283 ASCII 802 input 268 271 397 399 output 430 432 character code 133 character code list convert to atom 101 convert to number 374 character conversion define 135 136 query 174 character list convert to atom 99 convert to number 371 character set 793 character string read 281 characters meaning of Prolog specific 794 Prolog specific 794 special 794 close a Prolog list 741 command execute 552 554 command interpreter start 550 comments 796 end of line 796 variable length 796 compiler 155 complement 309 complex C function add to a module 708 configure debugger 208 tracer 576 conjunction 309 constant concatenation 159 syntax 799 test 117 constant pi 309 context create 166 quit 568 context jump initiate 568 intercept 131 control construct 125 127 243 580 conjunction 42 cut 39 disjunction 53 IF THEN conjunction 47 negation 71 368 cos 309 cosh 309 cosine 309 CPU time 309 cputime 309 create array 171 csize 309 current directory change 138 query 285 current module define 479 query 175 cursor position 356 389 563 cused 309 cut 39 cyclic term test 204 database size 309 database used 309 date determine 332 Deactivate breakpoint temporarily 640 debug
650. y Unify terms include cpred h BOOLEAN TermUnify TERM Termi TERM Term2 The function TermUnify unifies Term1 with Term2 If unification is successful the function returns TRUE otherwise it returns FALSE Arguments Term1 Term2 Term variables See also Term Unify Var Reference Manual 780 IF Prolog V5 3 TermUnify Atom C Function Active C interface Unify term with atom include cpred h BOOLEAN TermUnifyAtom TERM Term STRING Name The function TermUnifyAtom unifies the term Term with an atom with the name Name If unification is successful the function returns TRUE otherwise it returns FALSE Arguments Term Term variable Name String Hints The call of TermUnifyAtom Term Name is except for optimization identical to TermUnify Term TermMakeAtom Name See also TermUnify TermMakeAtom IF Prolog V5 3 781 Reference Manual Active C interface C Function TermUnifyCompound Unify term with structure include cpred h BOOLEAN TermUnifyCompound TERM Term STRING Functor ARITY Arity The function TermUnifyCompound unifies the term Term with a structure with the name Functor and the arity Arity the arguments of which are the terms passed in If one of the term variables passed in is NULL a new Prolog variable is used instead If unification is successful the function returns TRU
651. y preceded by the minus sign Floating point numbers are sequences of digits containing a decimal point or an exponent possibly preceded by the minus sign Octal numbers consist of a prefix 0o Zero o for octal and a sequence of octal digits from 0 to 7 the whole possibly preceded by the minus sign Hexadecimal numbers consist of a prefix Ox Zero x for hexa and a sequence of hex adecimal digits from 0 to 9 from a to f and from A to F the whole possibly preceded by the minus sign Rational numbers extension consist of a prefix Or Zero r and a ratio numerator denominator the whole possibly preceded by the minus sign Bracket pairs are used to denote structures and lists Character strings enclosed in double quotes are interpreted according to the value of the Prolog flag double_quotes The interpretation is either a list of character codes a list of characters or an atom Separators The Prolog system must be able to recognize the various lexical elements in Prolog during input in one of two ways e The beginning of a new lexical element must be recognizable Example female anna The opening parenthesis cannot belong to the token female IF Prolog V5 3 795 Reference Manual Prolog Syntax Basic Prolog elements e The individual elements must be separated from each other by means of explicit de limiters Example Xis5 Unless additional delimiters are specified Prolog will inte
652. yes user findall f a member X a b c L lt ENTER gt X _70 L f a f a f a lt ENTER gt yes The advantage of being able to insert any desired term for Term is that you can then refer to more than one variable in Goal user findall t X Y append X Y a b L lt ENTER gt X _68 Y _69 L t 0 a b t a b t a b lt ENTER gt yes Standard This predicate complies with the definition of the ISO standard for Prolog See also call 1 bagof 3 setof 3 2 2 set_prolog flag 2 IF Prolog V5 3 251 Reference Manual Term classification Predicate float 1 Test for floating point number float TestTerm The predicate float 1 succeeds if TestTerm is a floating point number otherwise it fails Arguments Test Term Term Example user float 5 0 lt ENTER gt yes user float 5 3 lt ENTER gt no user X is 5 3 0 float X lt ENTER gt X 15 lt ENTER gt yes Standard This predicate complies with the definition of the ISO standard for Prolog See also atom 1 atomic 1 compound 1 cyclic 1 ground 1 integer 1 nonvar 1 number 1 rational 1 var 1 Reference Manual 252 IF Prolog V5 3 float _format 2 Predicate Input output for terms Query and set floating point format float_format FormatOld FormatNew The predicate float_format 2 unifies FormatOld with the output format set for floatin
653. yes This is because IF Prolog inserts parentheses since both operators are right associative namely a b c The operators should now be redefined The right associative operators and are redefined as left associative operators user op 0 xfy lt ENTER gt yes user op 1100 yfx lt ENTER gt yes user op 0 xfy lt ENTER gt yes IF Prolog V5 3 381 Reference Manual Input output for terms Predicate op 3 user op 1100 yfx lt ENTER gt yes user a b c lt ENTER gt no The parentheses are now inserted from the left namely a b c Evaluation changes with the associativity Standard This predicate complies with the definition of the ISO standard for Prolog The use of arithmetic expressions in the argument Priority is not allowed in the ISO standard for Prolog In the ISO compatibility mode see Prolog flag iso therefore no arithmetic expressions may be used as arguments for this predicate Instead an evaluation must be programmed explicitly with the help of is 2 if necessary See also current_op 3 Reference Manual 382 IF Prolog V5 3 op 3 Directive Input output for terms Define and delete operators directive op Priority Assoc Names The directive op 3 can be used to define operators and delete operator definitions It is analogous to the predicate op 3 As as directive it is executed by consult 1 reconsult
654. ystem command 552 system 3 5 Execute an operating system command with input and output SpPeciNeEd s sa oe dle amp ee ee wee OU ome ee oe Re eke Se dos 554 system_hostid 1 Query machine identification 558 system_name 1 Query operating system 04 560 system_parameters 1 Query system parameters from IF Prolog call 561 tab 1 2 Move the cursor forward 025000000 563 Teli si Ser current cuipul Streami o sas kak kee ee ee ee Ee eR RDS 565 telling 1 Query current output stream 567 throw 1 Initiate a context jump gt s sos so socos ea eae eee es 568 timezone 4 Determine time and time zones 570 told 0 Reset current output stream 1 2 4 22 pee ee Re eee ee 572 trace 1 Activate tracing for a goal e a ede vee ew a a a 573 trace_begin 0 User defined tracer initialization ooo a aa 575 trace_config 3 Configure the tracer aooaa a 576 trace_end 0 User defined termination of the tracer 578 trace_output 4 User defined output predicate for the tracer 579 true 0 Goal which is always We s ose se ee BER ee eR ES Os 580 tty_size 2 3 Query the screen size aooaa a 581 unify_with_occurs_check 2 Unify terms with occurs check 583 nie fork l Spawn Poke lt o ssc p t ede EE eo Bw BOD Oe RDS 584 unix_getpid 1 Query process ID of current process
655. ystem dependent command interpreter UNIX sh and passes the specified Command to this interpreter for execution The predicate exec 2 starts the program Prog and passes to it the parameters specified in Args as arguments for its execution Arguments Command Atom Prog Atom Args List of atoms Exceptions instantiation_error The argument Command Prog Args or an element of Args must not be a variable but a variable was specified type_error atom The argument Command Prog or an element of Args must be an atom but is a term of another type type_error list The argument Args must be a list but is a term of another type system_error exec_failed The command Prog could not be started Possibly this is because the command could not be found in the current environment Hints Under UNIX the predicates exec 1 2 overlay IF Prolog in the current process with the new program Other operating systems may create a new process and terminate IF Prolog Under UNIX these predicates can be used in connection with unix_fork 1 which duplicates a process to implement communicating processes The predicate exec 1 is based on the C functions execl 2 and execlp 2 The predicate exec 2 is based on the C function execvp 2 see 10 Reference Manual 238 IF Prolog V5 3 exec 1 2 Predicate Operating system Example The predicates exec 1 unix_fork 1 and unix_wait 1 enable a predicate such as sys tem 1 to be implemented in

context/2 - bei IF Computer

Contents

Download Pdf Manuals

Related Search

Related Contents