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The Objective Caml system release 3.00 - The Caml language

1. c_vintr char c_vquit char c_verase char c_vkill char c_veof char c_veol char c_vmin int c_vtime int c_vstart char c_vstop char Output baud rate 0 means close connection Input baud rate Number of bits per character 5 8 Number of stop bits 1 2 Reception is enabled Enable parity generation and detection Specify odd parity instead of even Hang up on last close Ignore modem status lines Generate signal on INTR QUIT SUSP Enable canonical processing line buffering and editing Disable flush after INTR QUIT SUSP Echo input characters Echo ERASE to erase previous character Echo KILL to erase the current line Echo NL even if c_echo is not set Interrupt character usually ctr1 C Quit character usually ctrl Erase character usually DEL or ctrl H Kill line character usually ctrl U End of file character usually ctrl D Alternate end of line char usually none Minimum number of characters to read before the read request is satisfied Maximum read wait in 0 1s units Start character usually ctr1 Q Stop character usually ctrl S val tcgetattr file_descr gt terminal_io Return the status of the terminal referred to by the given file descriptor type setattr_when TCSANOW TCSADRAIN TCSAFLUSH val tcsetattr file_descr gt mode setat
2. XPIy Virtual method definition Method specification is written method private virtual method name typexpr It specifies whether the method is public or private and gives its type Constraints on type parameters The construct constraint typexpr typexpr forces the two type expressions to be equals This is typically used to specify type parameters they can be that way be bound to a specified type expression Initializers A class initializer initializer expr specifies an expression that will be evaluated when an object will be created from the class once all the instance variables have been initialized 6 9 3 Class definitions class definition class class binding and class binding class binding virtual type parameters class name pattern class type class expr type parameters ident ident A class definition class class binding and class binding is recursive Each class binding defines a class name that can be used in the whole expression except for inheritance It can also be used for inheritance but only in the definitions that follow its own A class binding binds the class name class name to the value of expression class expr It also binds the class type class name to the type of the class and defines two type abbreviations class name and class name The first one is the type of objects of this class while the second is more general as it unifies with the type of any obj
3. gt elt head tail gt if elt lt head then elt lst else head insert elt tail 55 val sort a list gt a list lt fun gt val insert a gt a list gt a list lt fun gt sort 1 string list a etc is tale told The type inferred for sort a list gt a list means that sort can actually apply to lists of any type and returns a list of the same type The type a is a type variable and stands for any given type The reason why sort can apply to lists of any type is that the comparisons lt etc are polymorphic in Caml they operate between any two values of the same type This makes sort itself polymorphic over all list types sort 6 2 5 3 int list 2 3 5 6 sort 3 14 2 718 float list 2 718000 3 140000 The sort function above does not modify its input list it builds and returns a new list con taining the same elements as the input list in ascending order There is actually no way in Caml to modify in place a list once it is built we say that lists are immutable data structures Most Caml data structures are immutable but a few most notably arrays are mutable meaning that they can be modified in place at any time 1 3 Functions as values Caml is a functional language functions in the full mathematical sense are supported and can be passed around freely just as any other piece of data For instance here is
4. iN of the sub array is identical to the element at coordinates iltofs iN of the original array a Genarray sub_left applies only to big arrays in C layout Raise Invalid_arg if ofs and len do not designate a valid sub array of a that is if ofs lt 0 or len lt 0 or ofs len gt Genarray nth_dim a 0 external sub_right Ca b fortran_layout t gt pos int gt len int gt a b fortran_layout t Extract a sub array of the given big array by restricting the last right most dimension Genarray sub_right a ofs len returns a big array with the same number of dimensions as a and the same dimensions as a except the last dimension which corresponds to the interval ofs ofs len 1 of the last dimension of a No copying of elements is involved the sub array and the original array share the same storage space In other terms the element at coordinates li1 iN of the sub array is identical to the element at coordinates li1 iN ofs of the original array a Genarray sub_right applies only to big arrays in Fortran layout Raise Invalid_arg if ofs and len do not designate a valid sub array of a that is if ofs lt 1 or len lt 0 or ofs len gt Genarray nth_dim a Genarray num_dims a 1 external slice_left Ca b c_layout t gt int array gt a b c_layout t Extract a sub array of lower dimension from the given big array by fixing one or several of the firs
5. Windows In addition to the text only command ocaml exe which works exactly as under Unix see above a graphical user interface for the toplevel is available under the name ocamlwin exe It should be launched from the Windows file manager or program manager The Terminal windows is split in two panes Phrases are entered and edited in the bottom pane The top pane displays a copy of the input phrases as they are processed by the Caml Light toplevel interspersed with the toplevel responses The Return key sends the contents of the bottom pane to the Caml Light toplevel The Enter key inserts a newline without Chapter 9 The toplevel system ocaml 141 sending the contents of the Input window This can be configured with the Preferences menu item The contents of the input window can be edited at all times with the standard Windows interface An history of previously entered phrases is maintained and displayed in a separate window To quit the Camlwin application either select Quit from the File menu or use the quit function described below At any point the parsing compilation or evaluation of the current phrase can be interrupted by selecting the Interrupt Caml Light menu item This goes back to the prompt 9 1 Options The following command line options are recognized by the ocaml command I directory Add the given directory to the list of directories searched for source and c
6. b gt event gt unit gt val mutable observers a list val mutable position int val mutable size int val mutable top bool method add_observer a gt unit method draw unit method identity int method move int gt unit method notify_observers event gt unit method raise unit method resize int gt unit end class subject richer_window_observer object inherit subject window_observer as super method notify s e if e lt gt Raise then s raise super notify s e end class a richer_window_observer object constraint a lt draw unit raise unit gt method notify a gt event gt unit end 82 We can also create a different kind of observer class subject trace_observer object inherit subject event observer method notify s e Printf printf lt Window d lt s gt n s identity string_of_event e end class a trace_observer object constraint a lt identity int gt method notify a gt event gt unit end and attached several observers to the same object let window new richer_window_subject val window lt notify a gt event gt unit _ gt richer_window_subject as a lt obj gt window tadd_observer new richer_window_observer unit QO window tadd_observer new trace_observer unit QO window move 1 window res
7. run Run the program until a breakpoint is hit or the program terminates step 0 Load the program and stop on the first event goto time Load the program and execute it until the given time Useful when you already know ap proximately at what time the problem appears Also useful to set breakpoints on function values that have not been computed at time 0 see section 15 5 The execution of a program is affected by certain information it receives when the debugger starts it such as the command line arguments to the program and its working directory The debugger provides commands to specify this information set arguments and cd These com mands must be used before program execution starts If you try to change the arguments or the working directory after starting your program the debugger will kill the program after asking for confirmation Chapter 15 The debugger ocamldebug 179 15 4 3 Running the program The following commands execute the program forward or backward starting at the current time The execution will stop either when specified by the command or when a breakpoint is encountered run Execute the program forward from current time Stops at next breakpoint or when the program terminates reverse Execute the program backward from current time Mostly useful to go to the last breakpoint encountered before the current time step count Run the program and stop at the next event With an argument do it count t
8. val gr_name string gr_passwd string gr_gid int gr_mem string array Structure of entries in the groups database getlogin unit gt string Return the login name of the user executing the process 310 val getpwnam string gt passwd_entry Find an entry in passwd with the given name or raise Not_found val getgrnam string gt group_entry Find an entry in group with the given name or raise Not_found val getpwuid int gt passwd_entry Find an entry in passwd with the given user id or raise Not_found val getgrgid int gt group_entry Find an entry in group with the given group id or raise Not_found Internet addresses type inet_addr The abstract type of Internet addresses val inet_addr_of_string string gt inet_addr val string_of_inet_addr inet_addr gt string Conversions between string with the format XXX YYY ZZZ TTT and Internet addresses inet_addr_of_string raises Failure when given a string that does not match this format val inet_addr_any inet_addr A special Internet address for use only with bind representing all the Internet addresses that the host machine possesses Sockets type socket_domain PF_UNIX Unix domain PF_INET Internet domain The type of socket domains type socket_type SOCK_STREAM Stream socket SOCK_DGRAM Datagram socket SOCK_RAW Raw socket SOCK_SEQPACKET Sequenced packets socket The type o
9. val max_int int val min_int int The greatest and smallest representable integers Bitwise operations val land int gt int gt int Bitwise logical and val lor int gt int gt int Bitwise logical or val lxor int gt int gt int Bitwise logical exclusive or val lnot int gt int Bitwise logical negation val 1sl int gt int gt int n ls1 m shifts n to the left by m bits val lsr int gt int gt int n lsr m shifts n to the right by m bits This is a logical shift zeroes are inserted regardless of the sign of n val asr int gt int gt int n asr m shifts n to the right by m bits This is an arithmetic shift the sign bit of n is replicated Chapter 18 The core library 227 Floating point arithmetic On most platforms Caml s floating point numbers follow the IEEE 754 standard using double precision 64 bits numbers Floating point operations do not fail on overflow or underflow but return denormal numbers val float gt float Unary negation You can also write e instead of e val float gt float gt float Floating point addition val float gt float gt float Floating point subtraction val float gt float gt float Floating point multiplication val float gt float gt float Floating point division val float gt float gt float Exponentiation val sqrt float gt float Square root
10. 59 else Node rprio relt left remove_top right let extract function Empty gt raise Queue_is_empty Node prio elt _ _ as queue gt prio elt remove_top queue end module PrioQueue sig type priority int and a queue Empty Node of priority a a queue a queue val empty a queue val insert a queue gt priority gt a gt a queue exception Queue_is_empty val remove_top a queue gt a queue val extract a queue gt priority a a queue end Outside the structure its components can be referred to using the dot notation that is identifiers qualified by a structure name For instance PrioQueue insert in a value context is the function insert defined inside the structure PrioQueue Similarly PrioQueue queue in a type context is the type queue defined in PrioQueue PrioQueue insert PrioQueue empty 1 hello string PrioQueue queue PrioQueue Node 1 hello PrioQueue Empty PrioQueue Empty 4 2 Signatures Signatures are interfaces for structures A signature specifies which components of a structure are accessible from the outside and with which type It can be used to hide some components of a structure e g local function definitions or export some components with a restricted type For instance the signature below specifies the three priority queue operations empty insert and extract but not the auxiliary function remo
11. Conditional The expression if expr then expr else expr evaluates to the value of expr if expr evaluates to the boolean true and to the value of exprs if expr evaluates to the boolean false The else expr part can be omitted in which case it defaults to else Case expression The expression match expr with pattern gt expr l pattern gt expr matches the value of expr against the patterns pattern to pattern If the matching against pattern succeeds the associated expression expr is evaluated and its value becomes the value of the whole match expression The evaluation of expr takes place in an environment enriched by the bindings performed during matching If several patterns match the value of expr the one that occurs first in the match expression is selected If none of the patterns match the value of expr the exception Match_failure is raised Boolean operators The expression expr amp amp expr evaluates to true if both expr and expr evaluate to true oth erwise it evaluates to false The first component expr is evaluated first The second com ponent expr is not evaluated if the first component evaluates to false Hence the expression expr amp amp expr behaves exactly as if expr then expr else false Chapter 6 The Objective Caml language 105 The expression expr expr evaluates to true if one of expr and expr evaluates to true otherwise it evaluates to false The firs
12. Unix_error exception 297 unlink 302 unlock 334 update 352 uppercase 244 290 usage 240 utimes 308 wait 299 335 337 wait_next_event 345 wait_pid 333 wait_read 333 wait_signal 333 wait_timed_read 333 wait_timed_write 333 wait_write 333 waitpid 299 337 Weak module 293 white 341 word_size 291 wrap 336 wrap_abort 336 write 300 337 yellow 341 yield 333 zero 262 264 277 INDEX OF KEYWORDS Index of keywords and see let type class 113 116 117 as 93 94 96 97 113 115 assert 127 begin 99 101 class 116 117 constraint 110 113 116 do see while for done see while for downto see for else see if end 99 101 112 113 117 118 121 122 exception 111 117 119 121 123 external 117 118 121 122 false 91 for 99 105 fun 99 100 102 113 function 99 100 102 functor 117 121 124 if 99 100 104 in see let 113 include 120 inherit 112 113 115 initializer 113 116 lazy 127 let 99 100 103 113 121 122 127 match 99 100 104 125 when 125 method 112 113 115 116 module 117 120 121 123 127 mutable 110 113 115 new 99 108 not 100 object 112 113 of see type exception open 117 120 121 124 385 or 99 100 105 parser 125 private 112 113 115 116 rec see let 113 sig 117 118 struct 121 122 then see if to see for true 91 try 99 100 105 type 109 117
13. eof Match the end of the lexer input Note On some systems with interactive input and end of file may be followed by more characters However ocamllex will not correctly handle regular expressions that contain eof followed by something else Chapter 12 Lexer and parser generators ocamllex ocamlyacc 159 string A string constant with the same syntax as Objective Caml string constants Match the corresponding sequence of characters character set Match any single character belonging to the given character set Valid character sets are single character constants c ranges of characters c1 c2 all characters between c and c2 inclusive and the union of two or more character sets denoted by concatenation character set Match any single character not belonging to the given character set regexp Repetition Match the concatenation of zero or more strings that match regexp regexp Strict repetition Match the concatenation of one or more strings that match regexp regexp Option Match either the empty string or a string matching regexp regexp regexp Alternative Match any string that matches either regexp or regexp regexp regexp Concatenation Match the concatenation of two strings the first matching regexp the second matching regexps regexp Match the same strings as regexp ident Reference the regular expression bound to ident by an earlier let ident
14. gt a gt a gt bool lt a gt a gt bool gt a gt a gt bool Structural ordering functions These functions coincide with the usual orderings over integers characters strings and floating point numbers and extend them to a total ordering over all types The ordering is compatible with As in the case of mutable structures are compared by contents Comparison between functional values raises Invalid_argument Comparison between cyclic structures may not terminate compare a gt a gt int compare x y returns 0 if x y a negative integer if x lt y and a positive integer if x gt y The same restrictions as for apply compare can be used as the comparison function required by the Set and Map modules min a gt a gt a Return the smaller of the two arguments max a gt a gt a Return the greater of the two arguments a gt a gt bool e1 e2 tests for physical equality of e1 and e2 On integers and characters it is the same as structural equality On mutable structures e1 e2 is true if and only if physical modification of e1 also affects e2 On non mutable structures the behavior of is implementation dependent except that e1 e2 implies e1 e2 a gt a gt bool Negation of Chapter 18 The core library 225 Boolean operations val not bool gt bool The boolean negation val amp amp
15. object val mutable x x_init method get x method set y x lt y end Some type variables are unbound in this type class ref a gt object val mutable x a method get a method set a gt unit end The method get has type a where a is unbound The reason is that at least one of the methods has a polymorphic type here the type of the value stored in the reference cell thus the class should be parametric or the method type should be constrained to a monomorphic type A monomorphic instance of the class could be defined by class ref x_init int object val mutable x x_init method get x method set y x lt y end class ref int gt object val mutable x int method get int method set int gt unit end A class for polymorphic references must explicitly list the type parameters in its declaration Class type parameters are always listed between and The type parameters must also be bound somewhere in the class body by a type constraint class a ref x_init object val mutable x x_init a method get x method set y x lt y end class a ref a gt object val mutable x a method get a method set a gt unit end let r new ref 1 in r set 2 r get int 2 The type parameter in the declaration may actually be constrained in the body of the class def inition In the class type the
16. object self method copy Oo copy self end class copy object a method copy a end Chapter 3 Objects in Caml 53 Only the override can be used to actually override fields and only the 0o copy primitive can be used externally Cloning can also be used to provide facilities for saving and restoring the state of objects class backup object self mytype val mutable copy None method save copy lt Some lt copy None gt method restore match copy with Some x gt x None gt self end class backup object a val mutable copy a option method restore a method save unit end The above definition will only backup one level The backup facility can be added to any class using multiple inheritance class a backup_ref x object inherit a ref x inherit backup end class a backup_ref a gt object b val mutable copy b option val mutable x a method get a method restore b method save unit method set a gt unit end let rec get p n if n 0 then p get else get p restore n 1 val get lt get b restore a gt as a gt int gt b lt fun gt let p new backup_ref O in p save p set 1 p save p set 2 get p 0 get p 1 get p 2 get p 3 get p 4 int list 2 1 1 1 1 A variant of backup could retain all copies We then add a method clea
17. val execvp prog string gt args string array gt unit val execvpe prog string gt args string array gt env string array gt unit Same as execv and execvp respectively except that the program is searched in the path Chapter 20 The unix library Unix system calls 299 val fork unit gt int Fork a new process The returned integer is 0 for the child process the pid of the child process for the parent process val wait unit gt int process_status Wait until one of the children processes die and return its pid and termination status val waitpid mode wait_flag list gt int gt int process_status Same as wait but waits for the process whose pid is given A pid of 1 means wait for any child A pid of 0 means wait for any child in the same process group as the current process Negative pid arguments represent process groups The list of options indicates whether waitpid should return immediately without waiting or also report stopped children val system string gt process_status Execute the given command wait until it terminates and return its termination status The string is interpreted by the shell bin sh and therefore can contain redirections quotes variables etc The result WEXITED 127 indicates that the shell couldn t be executed val getpid unit gt int Return the pid of the process val getppid unit gt int Return the pid of the parent process val nice int gt int
18. val exp float gt float val log float gt float val log10 float gt float Exponential natural logarithm base 10 logarithm val cos float gt float val sin float gt float val tan float gt float val acos float gt float val asin float gt float val atan float gt float val atan2 float gt float gt float The usual trignonmetric functions 228 val val val val val val val val val val val val val val cosh float gt float sinh float gt float tanh float gt float The usual hyperbolic trigonometric functions ceil float gt float floor float gt float Round the given float to an integer value floor f returns the greatest integer value less than or equal to f ceil f returns the least integer value greater than or equal to f abs_float float gt float Return the absolute value of the argument mod_float float gt float gt float mod_float a b returns the remainder of a with respect to b The returned value is a n b where n is the quotient a b rounded towards zero to an integer frexp float gt float int frexp f returns the pair of the significant and the exponent of f When f is zero the significant x and the exponent n of f are equal to zero When f is non zero they are defined by f x 2 nandO 5 lt x lt 1 0 ldexp float gt int gt float ldexp x n returns x 2 n modf
19. bool gt bool gt bool val amp bool gt bool gt bool The boolean and Evaluation is sequential left to right in e1 amp amp e2 e1 is evaluated first and if it returns false e2 is not evaluated at all val I bool gt bool gt bool val or bool gt bool gt bool The boolean or Evaluation is sequential left to right in e1 e2 e1 is evaluated first and if it returns true e2 is not evaluated at all Integer arithmetic Integers are 31 bits wide or 63 bits on 64 bit processors All operations are taken modulo 231 or 263 They do not fail on overflow val int gt int Unary negation You can also write e instead of e val succ int gt int succ x is x 1 val pred int gt int pred x is x 1 val int gt int gt int Integer addition val int gt int gt int Integer subtraction val int gt int gt int Integer multiplication val int gt int gt int Integer division Raise Division_by_zero if the second argument is 0 226 val mod int gt int gt int Integer remainder If x gt 0 and y gt 0 the result of x mod y satisfies the following properties 0 lt x mod y lt yand x x y y x mod y Ify 0 x mod y raises Division_by_zero If x lt O or y lt 0 the result of x mod y is not specified and depends on the platform val abs int gt int Return the absolute value of the argument
20. gt h int gt unit draw_rect x y w h draws the rectangle with lower left corner at x y width w and height h The current point is unchanged draw_arc x int gt y int gt rx int gt ry int gt start int gt stop int gt unit draw_arc x y rx ry al a2 draws an elliptical arc with center x y horizontal radius rx vertical radius ry from angle a1 to angle a2 in degrees The current point is unchanged Chapter 24 The graphics library 343 val draw_ellipse x int gt y int gt rx int gt ry int gt unit draw_ellipse x y rx ry draws an ellipse with center x y horizontal radius rx and vertical radius ry The current point is unchanged val draw_circle x int gt y int gt r int gt unit draw_circle x y r draws a circle with center x y and radius r The current point is unchanged val set_line_width int gt unit Set the width of points and lines drawn with the functions above Under X Windows set_line_width 0 selects a width of 1 pixel and a faster but less precise drawing algorithm than the one used when set_line_width 1 is specified Text drawing val draw_char char gt unit val draw_string string gt unit Draw a character or a character string with lower left corner at current position After drawing the current position is set to the lower right corner of the text drawn val set_font string gt unit val set_text_size int gt unit Set the font and character size used f
21. gt int64 gt string Int64 format fmt n return the string representation of the 64 bit integer n in the format specified by fmt fmt is a Printf style format containing exactly one d i u 4x AX or 0 conversion specification See the documentation of the Printf module for more information 19 14 Module Lazy deferred computations type a status Delayed of unit gt a Value of a Exception of exn type a t a status ref A value of type a Lazy t is a deferred computation also called a suspension that computes a result of type a The expression lazy expr returns a suspension that computes expr exception Undefined val force at gt a Lazy force x computes the suspension x and returns its result If the suspension was already computed Lazy force x returns the same value again If it raised an exception the same exception is raised again Raise Undefined if the evaluation of the suspension requires its own result 268 19 15 Module Lexing the run time library for lexers generated by ocamllex Lexer buffers type lexbuf refill_buff lexbuf gt unit mutable lex_buffer string mutable lex_buffer_len int mutable lex_abs_pos int mutable lex_start_pos int mutable lex_curr_pos int mutable lex_last_pos int mutable lex_last_action int mutable lex_eof_reached bool The type of lexer buffers A lexer buffer is the argument passed to the scanning
22. val setitimer interval_timer gt interval_timer_status gt interval_timer_status setitimer t s sets the interval timer t and returns its previous status The s argument is interpreted as follows s it_value if nonzero is the time to the next timer expiration s it_interval if nonzero specifies a value to be used in reloading it_value when the timer expires Setting s it_value to zero disable the timer Setting s it_interval to zero causes the timer to be disabled after its next expiration Chapter 20 The unix library Unix system calls 309 User id group id val val val val val val val getuid unit gt int Return the user id of the user executing the process geteuid unit gt int Return the effective user id under which the process runs setuid int gt unit Set the real user id and effective user id for the process getgid unit gt int Return the group id of the user executing the process getegid unit gt int Return the effective group id under which the process runs setgid int gt unit Set the real group id and effective group id for the process getgroups unit gt int array Return the list of groups to which the user executing the process belongs type passwd_entry pw_name string pw_passwd string pw_uid int pw_gid int pw_gecos string pw_dir string pw_shell string Structure of entries in the passwd database type group_entry
23. value caml_stub value bigarray int dimx Bigarray_val bigarray gt dim 0 int dimy Bigarray_val bigarray gt dim 1 C passes scalar parameters by value my_c_function Data_bigarray_val bigarray dimx dimy Fortran passes all parameters by reference my_fortran_function_ Data_bigarray_val bigarray amp dimx amp dimy return Val_unit 28 2 3 Wrapping a C or Fortran array as a Caml big array A pointer p to an already allocated C or Fortran array can be wrapped and returned to Caml as a big array using the alloc_bigarray or alloc_bigarray_dims functions e alloc_bigarray kind layout numdims p dims Return a Caml big array wrapping the data pointed to by p kind is the kind of array elements one of the BIGARRAY_ kind constants above layout is BIGARRAY_C_LAYOUT for an array with C layout and BIGARRAY_FORTRAN_LAYOUT for an array with Fortran layout numdims is the number of dimensions in the array dims is an array of numdims long integers giving the sizes of the array in each dimension e alloc_bigarray_dims kind layout numdims p long dim long dima Long diMnumdims Same as alloc_bigarray but the sizes of the array in each dimension are listed as extra arguments in the function call rather than being passed as an array The following example illustrates how statically allocated C and Fortran arrays can be made avail able to Caml Chapter 28 The bigarray library 371 extern
24. 25 26 2 1 1 Classic mode In Objective Caml there are two ways of using labels either the default classic mode or the commuting label mode You need do nothing special to be in classic mode and legacy programs written for previous versions of Objective Caml will work with no modifications in this mode Indeed all the first chapter was written in this mode In the classic mode labels need not be explicitly written in function applications but whenever they are given they are checked against the labels in the function type f 3 25 int 1 f x 3 Z 23 Expecting function has type y int gt int This argument cannot be applied with label z The above error message gives the the type of the function applied to its previous arguments here x and the position of the unexpected argument Similar processing is done for functions defined inside an application If you define inline a function with labels they are checked against the labels expected by the enclosing function Hashtbl iter key a gt data b gt unit gt a b Hashtbl t gt unit lt fun gt let print_all tbl Hashtbl iter f fun key data gt Printf printf s s n key data tbl val print_all string string Hashtbl t gt unit lt fun gt let print_all tbl Hashtbl iter f fun data key gt Printf printf s s n key data tbl This function should have type key a gt data
25. Change the process priority The integer argument is added to the nice value Higher values of the nice value mean lower priorities Return the new nice value Basic file input output type file_descr The abstract type of file descriptors val stdin file_descr val stdout file_descr val stderr file_descr File descriptors for standard input standard output and standard error 300 type open_flag O_RDONLY Open for reading O_WRONLY Open for writing O_RDWR Open for reading and writing O_NONBLOCK Open in non blocking mode O_APPEND Open for append O_CREAT Create if nonexistent O_TRUNC Truncate to 0 length if existing O_EXCL Fail if existing The flags to open type file_perm int The type of file access rights val openfile string gt mode open_flag list gt perm file_perm gt file_descr Open the named file with the given flags Third argument is the permissions to give to the file if it is created Return a file descriptor on the named file val close file_descr gt unit Close a file descriptor val read file_descr gt buf string gt pos int gt len int gt int read fd buff ofs len reads len characters from descriptor fd storing them in string buff starting at position ofs in string buff Return the number of characters actually read val write file_descr gt buf string gt pos int gt len int gt int write f
26. Convert the given native integer type nativeint to an integer type int The high order bit is lost during the conversion of_float float gt nativeint Convert the given floating point number to a native integer discarding the fractional part truncate towards 0 The result of the conversion is undefined if after truncation the number is outside the range Nativeint min_int Nativeint max_int Chapter 19 The standard library 279 val to_float nativeint gt float Convert the given native integer to a floating point number val of_int32 int32 gt nativeint Convert the given 32 bit integer type int32 to a native integer val to_int32 nativeint gt int32 Convert the given native integer to a 32 bit integer type int32 On 64 bit platforms the 64 bit native integer is taken modulo 232 i e the top 32 bits are lost On 32 bit platforms the conversion is exact val of_string string gt nativeint Convert the given string to a native integer The string is read in decimal by default or in hexadecimal octal or binary if the string begins with Ox Oo or Ob respectively Raise Failure int_of_string if the given string is not a valid representation of an integer val to_string nativeint gt string Return the string representation of its argument in decimal val format string gt nativeint gt string Nativeint format fmt n return the string representation of the native integer n in the format specified
27. Guards occur just before the gt token and are introduced by the when keyword function pattern when condi gt expr pattern when cond gt expr Matching proceeds as described before except that if the value matches some pattern pattern which has a guard cond then the expression cond is evaluated in an environment enriched by the bindings performed during matching If cond evaluates to true then expr is evaluated and its value returned as the result of the matching as usual But if cond evaluates to false the matching is resumed against the patterns following pattern Local definitions The let and let rec constructs bind value names locally The construct let pattern expr and and pattern expr in expr evaluates expr expr in some unspecified order then matches their values against the patterns pattern pattern If the matchings succeed expr is evaluated in the environment enriched by the bindings performed during matching and the value of expr is returned as the value of the whole let expression If one of the matchings fails the exception Match_failure is raised An alternate syntax is provided to bind variables to functional values instead of writing let ident fun parameter parameter gt expr in a let expression one may instead write let ident parameter parameter expr Recursive definitions of names are introduced by let rec let rec pattern expr and and patte
28. I 3 0 4 0 float array 4 000000 6 000000 Record fields can also be modified by assignment provided they are declared mutable in the definition of the record type type mutable_point mutable x float mutable y float type mutable_point mutable x float mutable y float let translate p dx dy p x lt p x dx p y lt p y dy val translate mutable_point gt float gt float gt unit lt fun gt let mypoint x 0 0 y 0 0 val mypoint mutable_point x 0 000000 y 0 000000 translate mypoint 1 0 2 0 unit mypoint mutable_point x 1 000000 y 2 000000 Caml has no built in notion of variable identifiers whose current value can be changed by assignment The let binding is not an assignment it introduces a new identifier with a new scope However the standard library provides references which are mutable indirection cells or one element arrays with operators to fetch the current contents of the reference and to assign the contents Variables can then be emulated by let binding a reference For instance here is an in place insertion sort over arrays Chapter 1 The core language 17 a j lt val_i let insertion_sort a for i 1 to Array length a 1 do let val_i a i in let j ref i in while j gt O amp amp val_i lt a j 1 do a j lt a j 1 JaSt t done d
29. Nil Cons of a Snoc of b gt gt A of gt Nil Cons of a B of gt Snoc of b lt fun gt When an or pattern composed of variant tags is wrapped inside an alias pattern the alias is given a type containing only the tags enumerated in the or pattern this allows for many useful idioms like incremental definition of functions let num x Num x let evali eval Num x x let rec eval x evall eval x val num a gt gt Num of a lt fun gt val evall a gt lt Num of b gt b lt fun gt val eval lt Num of a gt a lt fun gt let plus x y Plus x y let eval2 eval function Plus x y gt eval x eval y Num _ as x gt evali eval x let rec eval x eval2 eval x val plus a gt b gt gt Plus of a b lt fun gt val eval2 a gt int gt lt Plus of a a Num of int gt int lt fun gt val eval lt Plus of a a Num of int as a gt int lt fun gt To make this even more confortable you may use type definitions as abbreviations for or patterns That is if you have defined type myvariant Tagi int Tag2 bool then the pattern myvariant is equivalent to writing Tagi _ int Tag2 _ bool Such abbreviations may be used alone let f function myvariant gt myvaria
30. See also the set arguments command The following command line options are recognized 175 176 I directory Add directory to the list of directories searched for source files and compiled files See also the directory command s socket Use socket for communicating with the debugged program See the description of the com mand set socket section 15 8 6 for the format of socket c count Set the maximum number of simultaneously live checkpoints to count cd directory Run the debugger program from the working directory directory instead of the current di rectory See also the cd command emacs Tell the debugger it is executed under Emacs See section 15 10 for information on how to run the debugger under Emacs 15 2 2 Exiting the debugger The command quit exits the debugger You can also exit the debugger by typing an end of file character usually ctr1 D Typing an interrupt character usually ctr1 C will not exit the debugger but will terminate the action of any debugger command that is in progress and return to the debugger command level 15 3 Commands A debugger command is a single line of input It starts with a command name which is followed by arguments depending on this name Examples run goto 1000 set arguments arg1 arg2 A command name can be truncated as long as there is no ambiguity For instance go 1000 is understood as goto 1000 since there are no other commands whose name starts with g
31. The graphics window is cleared and the current point is set to 0 0 The string argument is used to pass optional information on the desired graphics mode the graphics window size and so on Its interpretation is implementation dependent If the empty string is given a sensible default is selected val close_graph unit gt unit Delete the graphics window or switch the screen back to text mode val clear_graph unit gt unit Erase the graphics window Chapter 24 The graphics library 341 val size_x unit gt int val size_y unit gt int Return the size of the graphics window Coordinates of the screen pixels range over O size_x 1 and0 size_y 1 Drawings outside of this rectangle are clipped without causing an error The origin 0 0 is at the lower left corner Colors type color int A color is specified by its R G B components Each component is in the range 0 255 The three components are packed in an int OxRRGGBB where RR are the two hexadecimal digits for the red component GG for the green component BB for the blue component val rgb int gt int gt int gt color rgb r g b returns the integer encoding the color with red component r green component g and blue component b r g and b are in the range 0 255 val set_color color gt unit Set the current drawing color val black color val white color val red color val green color val blue color val yellow color
32. The syntax a with one two or three coordinates is reserved for accessing one two and three dimensional arrays as described below external set a b c t gt int array gt a gt unit Assign an element of a generic big array Genarray set a il iNI v stores the value v in the element of a whose coordinates are i1 in the first dimension i2 in the second dimension iN in the N th dimension The array a must have exactly N dimensions and all coordinates must lie inside the array bounds as described for Genarray get otherwise Invalid_arg is raised If N gt 3 alternate syntax is provided you can write a il i2 iN lt v instead of Genarray set a i1l iN v The syntax a lt v with one two or three coordinates is reserved for updating one two and three dimensional arrays as described below external sub_left Ca b c_layout t gt pos int gt len int gt a b c_layout t Extract a sub array of the given big array by restricting the first left most dimension Genarray sub_left a ofs len returns a big array with the same number of dimensions as a and the same dimensions as a except the first dimension which corresponds to the interval ofs ofs len 1 of the first dimension of a No copying of elements is involved the sub array and the original array share the same storage space In other terms 362 the element at coordinates i1
33. This error appears when trying to link an incomplete or incorrectly ordered set of files Either you have forgotten to provide an implementation for the compilation unit named mod on the command line typically the file named mod cmo or a library containing that file Fix add the missing ml or cmo file to the command line Or you have provided an implementation for the module named mod but it comes too late on the command line the implementation of mod must come before all bytecode object files that reference mod Fix change the order of ml and cmo files on the command line Of course you will always encounter this error if you have mutually recursive functions across modules That is function Mod1 f calls function Mod2 g and function Mod2 g calls function 138 Modi f In this case no matter what permutations you perform on the command line the program will be rejected at link time Fixes e Put f and g in the same module e Parameterize one function by the other That is instead of having modi ml let f x Mod2 g mod2 m1 let g y Mod1 f define modi ml let fgx mod2 m1 let rec g y Modi fg and link mod1 cmo before mod2 cmo e Use a reference to hold one of the two functions as in modi ml let forward_g ref fun x gt failwith forward_g lt type gt let f x forward_g mod2 m1 let g y Mod1 f let _ Mod1 forward_g g This will not work if g is a polymorphi
34. This flag has no effect when linking already compiled files noautolink When linking cmxa libraries ignore cclib and ccopt options potentially contained in the libraries if these options were given when building the libraries This can be useful 154 if a library contains incorrect specifications of C libraries or C options in this case during linking set noautolink and pass the correct C libraries and options on the command line o exec file Specify the name of the output file produced by the linker The default output name is a out in keeping with the Unix tradition If the a option is given specify the name of the library produced If the output obj option is given specify the name of the output file produced output obj Cause the linker to produce a C object file instead of an executable file This is useful to wrap Caml code as a C library callable from any C program See chapter 17 section 17 7 5 The name of the output object file is camlprog o by default it can be set with the o option p Generate extra code to write profile information when the program is executed The profile information can then be examined with the analysis program gprof See chapter 16 for more information on profiling The p option must be given both at compile time and at link time Linking object files not compiled with p is possible but results in less precise profiling Unix See the Unix manual page for gprof 1 for more in
35. Weak check ar n returns true if the nth cell of ar is full false if it is empty Note that even if Weak check ar n returns true a subsequent Weak get ar n can return None val fill a t gt pos int gt len int gt a option gt unit Weak fill ar ofs len el sets to el all pointers of ar from ofs to ofs len 1 Raise Invalid_argument Weak fill if ofs and len do not designate a valid subarray of a val blit src a t gt src_pos int gt dst a t gt dst_pos int gt len int gt unit Weak blit ari off1 ar2 off2 len copies len weak pointers from ar1 starting at off1 to ar2 starting at of 2 It works correctly even if ar1 and ar2 are the same Raise Invalid_argument Weak blit if off1 and len do not designate a valid subarray of ar1 or if of f2 and len do not designate a valid subarray of ar2 294 Chapter 20 The unix library Unix system calls The unix library makes many Unix system calls and system related library functions available to Objective Caml programs This chapter describes briefly the functions provided Refer to sections 2 and 3 of the Unix manual for more details on the behavior of these functions Not all functions are provided by all Unix variants If some functions are not available they will raise Invalid_arg when called Programs that use the unix library must be linked as follows ocamlc other options unix cma other files ocamlopt other options unix cmxa other files For
36. a val send a channel gt a gt unit event send ch v returns the event consisting in sending the value v over the channel ch The result value of this event is val receive a channel gt a event receive ch returns the event consisting in receiving a value from the channel ch The result value of this event is the value received 336 val val val val val val val val always a gt a event always v returns an event that is always ready for synchronization The result value of this event is v choose a event list gt a event choose evl returns the event that is the alternative of all the events in the list evl wrap a event gt f a gt b gt b event wrap ev fn returns the event that performs the same communications as ev then applies the post processing function fn on the return value wrap_abort a event gt f unit gt unit gt a event wrap_abort ev fn returns the event that performs the same communications as ev but if it is not selected the function fn is called after the synchronization guard unit gt a event gt a event guard fn returns the event that when synchronized computes fn and behaves as the resulting event This allows to compute events with side effects at the time of the synchronization operation sync a event gt a Synchronize on an event offer all the communication possibilitie
37. argv Do some computation result fib 10 printf fib 10 s n format_result result return 0 To build the whole program just invoke the C compiler as follows cc o prog main c mod a lcurses On some machines you may need to put 1termcap or lcurses ltermcap instead of lcurses 17 9 Advanced topic custom blocks Blocks with tag Custom_tag contain both arbitrary user data and a pointer to a C struct with type struct custom_operations that associates user provided finalization comparison hashing serialization and deserialization functions to this block 17 9 1 The struct custom_operations The struct custom_operations is defined in lt cam1 custom h gt and contains the following fields e char identifier A zero terminated character string serving as an identifier for serialization and deserialization operations e void finalize value v The finalize field contains a pointer to a C function that is called when the block becomes unreachable and is about to be reclaimed The block is passed as first argument to the function The finalize field can also be NULL to indicate that no finalization function is associated with the block e int compare value v1 value v2 The compare field contains a pointer to a C function that is called whenever two custom blocks are compared using Caml s generic comparison operators lt gt lt gt lt gt and compare The C function should return 0
38. as long as their role is clear from the function s name Here are some of the label names you will find throughout the libraries Label Meaning f a function to be applied pos a position in a string or array len a length buf a string used as buffer src the source of an operation dst the destination of an operation cmp a comparison function e g Pervasives compare key a value used as index data a value associated to an index mode an operation mode or a flag list perm file permissions ms a duration in milliseconds Chapter 2 Labels and variants 31 All these are only suggestions but one shall keep in mind that the choice of labels is essential for readability Bizarre choices will make the program harder to maintain In the ideal the right function name with right labels shall be enough to understand the function s meaning Since one can get this information with OCamlBrowser or the ocam1 toplevel the documentation is only used when a more detailed specification is needed 2 2 Polymorphic variants Variants as presented in section 1 4 are a powerful tool to build data structures and algorithms However they sometimes lack flexibility when used in modular programming This is due to the fact every constructor reserves a name to be used with a unique type On cannot use the same name in another type or consider a value of some type to belong to some other type with more constructo
39. evaluate print_newline to close all remaining boxes and flush the pretty printer The behaviour of pretty printing commands is unspecified if there is no opened pretty printing box Each box opened via one of the open_ functions below must be closed using close_box for proper formatting Otherwise some of the material printed in the boxes may not be output or may be formatted incorrectly In case of interactive use the system closes all opened boxes and flushes all pending text as with the print_newline function after each phrase Each phrase is therefore executed in the initial state of the pretty printer Boxes val open_box int gt unit open_box d opens a new pretty printing box with offset d This box is the general purpose pretty printing box Material in this box is displayed horizontal or vertical break hints inside the box may lead to a new line if there is no more room on the line to print the remainder of the box or if a new line may lead to a new indentation demonstrating the indentation of the box When a new line is printed in the box d is added to the current indentation 248 val close_box unit gt unit Close the most recently opened pretty printing box Formatting functions val print_string string gt unit print_string str prints str in the current box val print_as int gt string gt unit print_as len str prints str in the current box The pretty printer formats str as i
40. gt gt module expr Module type definitions A definition for a module type is written module type modtype name module type It binds the name modtype name to the module type denoted by the expression module type 124 Opening a module path The expression open module path in a structure does not define any components nor perform any bindings It simply affects the parsing of the following items of the structure allowing components of the module denoted by module path to be referred to by their simple names name instead of path accesses module path name The scope of the open stops at the end of the structure expression 6 11 3 Functors Functor definition The expression functor module name module type gt module expr evaluates to a functor that takes as argument modules of the type module type binds module name to these modules evaluates module expr in the extended environment and returns the resulting modules as results No restrictions are placed on the type of the functor argument in particular a functor may take another functor as argument higher order functor Functor application The expression module expr module expry evaluates module expr to a functor and module expr to a module and applies the former to the latter The type of module expry must match the type expected for the arguments of the functor module expry 6 12 Compilation units unit interface specification unit i
41. gt int pp_over_max_boxes formatter gt unit gt bool pp_set_ellipsis_text formatter gt string gt unit pp_get_ellipsis_text formatter gt unit gt string pp_set_formatter_out_channel formatter gt out_channel gt unit 254 val val val val val pp_set_formatter_output_functions formatter gt out buf string gt pos int gt len int gt unit gt flush unit gt unit gt unit pp_get_formatter_output_functions formatter gt unit gt buf string gt pos int gt len int gt unit unit gt unit pp_set_all_formatter_output_functions formatter gt out buf string gt pos int gt len int gt unit gt flush unit gt unit gt newline unit gt unit gt space int gt unit gt unit pp_get_all_formatter_output_functions formatter gt unit gt buf string gt pos int gt len int gt unit unit gt unit unit gt unit int gt unit The basic functions to use with formatters These functions are the basic ones usual functions operating on the standard formatter are defined via partial evaluation of these primitives For instance print_string is equal to pp_print_string std_formatter fprintf formatter gt a formatter unit format gt a fprintf ff format argi argN formats the arguments arg1 to argN according to the format string format and outputs the resulting string on th
42. its components are evaluated each time an object is created In a class body the pattern pattern typexpr is matched against self therefore provinding a binding for self and self type Self can only be used in method and initializers Self type cannot be a closed object type so that the class remains extensible Inheritance The inheritance construct inherit class expr allows to reuse methods and instance variables from other classes The class expression class expr must evaluate to a class body The instance variables methods and initializers from this class body are added into the current class The addition of a method will override any previously defined methods of the same name An ancestor can be bound by prepending the construct as value name to the inheritance con struct above value name is not a true variable and can only be used to select a method i e in an expression value name method name This gives access to the method method name as it was defined in the parent class even if it is redefined in the current class The scope of an ancestor binding is limited to the current class The ancestor method may be called from a subclass but only indirectly Instance variable definition The definition val mutable inst var name expr adds an instance variable inst var name whose initial value is the value of expression expr Several variables of the same name can be defined in the same class The flag mutable allows physica
43. lt inst var name expr inst var name expr gt returns a copy of self with the given instance variables replaced by the values of the associated expressions other instance variables have the same value in the returned object as in self 6 8 Type and exception definitions 6 8 1 Type definitions Type definitions bind type constructors to data types either variant types record types type abbreviations or abstract data types They also bind the value constructors and record fields associated with the definition 110 type definition type typedef and typedef typedef type params typeconstr name type information type information type equation type representation type constraint type equation typexpr type representation constr decl constr decl field decl field decl type params ident ident ident constr decl cconstr name nceconstr name of typexpr field decl field name typexpr mutable field name typexpr type constraint constraint ident typexpr Type definitions are introduced by the type keyword and consist in one or several simple definitions possibly mutually recursive separated by the and keyword Each simple definition defines one type constructor A simple definition consists in a lowercase identifier possibly preceded by one or several type parameters and followed by an optional type equation then an optional type
44. method name is the name of the method and typexpr its expected type Constraints on type parameters The construct constraint typexpr typexpr forces the two type expressions to be equals This is typically used to specify type parameters they can be that way be bound to a specified type expression 6 9 2 Class expressions Class expressions are the class level equivalent of value expressions they evaluate to classes thus providing implementations for the specifications expressed in class types 114 class expr class path typexpr typexpr class path class expr class expr class type class expr argument fun parameter gt class expr let rec let binding and let binding in class expr object pattern typexpr class field end class field inherit class expr as value name val mutable inst var name expr method private method name pattern expr method private virtual method name typexpr constraint typexpr typexpr initializer expr Simple class expressions The expression class path evaluates to the class bound to the name class path Similarly the ex pression typexpr typexpr class path evaluates to the parametric class bound to the name class path in which type parameters have been instanciated to respectively typexpr typexpr The expression class expr evaluates to the same module as class expr The expression class expr class type
45. nativeint Predecessor Nativeint pred x is Nativeint sub x 1n abs nativeint gt nativeint Return the absolute value of its argument 278 val val val val val val val val val val val val max_int nativeint The greatest representable native integer either 231 1 on a 32 bit platform or 263 1 ona 64 bit platform min_int nativeint 931 The greatest representable native integer either 2 on a 32 bit platform or 2 on a 64 bit platform logand nativeint gt nativeint gt nativeint Bitwise logical and logor nativeint gt nativeint gt nativeint Bitwise logical or logxor nativeint gt nativeint gt nativeint Bitwise logical exclusive or lognot nativeint gt nativeint Bitwise logical negation shift_left nativeint gt int gt nativeint Nativeint shift_left x y shifts x to the left by y bits shift_right nativeint gt int gt nativeint Nativeint shift_right x y shifts x to the right by y bits This is an arithmetic shift the sign bit of x is replicated and inserted in the vacated bits shift_right_logical nativeint gt int gt nativeint Nativeint shift_right_logical x y shifts x to the right by y bits This is a logical shift zeroes are inserted in the vacated bits regardless of the sign of x of_int int gt nativeint Convert the given integer type int to a native integer type nativeint to_int nativeint gt int
46. new account x in if today lt 1998 10 30 then c deposit m 100 c end end HHH HH HHH HHH HH HH HHH HHH HHH HH HH HH HH HHH HH OH OF OH OH OH OF OF balance lt balance plus neg x self trace Retrieval x x 71 This shows the use of modules to group several class definitions that can in fact be thought of as 72 a single unit This unit would be provided by a bank for both internal and external uses This is implemented as a functor that abstracts over the currency so that the same code can be used to provide accounts in different currencies The class bank is the real implementation of the bank account it could have been inlined This is the one that will be used for further extensions refinements etc Conversely the client will only be given the client view module Euro_account Account Euro module Client Euro_account Client Euro_account new Client account new Euro c 100 Hence the clients do not have direct access to the balance nor the history of their own accounts Their only way to change their balance is to deposit or withdraw money It is important to give the clients a class and not just the ability to create accounts such as the promotional discount account so that they can personalize their account For instance a client may refine the deposit and withdraw methods so as to do his own financial bookkeeping automatically On the other hand the function discount is given
47. nodes were encountered or m nodes meaningful or not were encountered Meaningful nodes are integers floating point numbers strings characters booleans and constant constructors Larger values of m and n means that more nodes are taken into account to compute the final hash value and therefore collisions are less likely to happen However hashing takes longer The parameters m and n govern the tradeoff between accuracy and speed This module provides operations on the type int32 of signed 32 bit integers Unlike the built in int type the type int32 is guaranteed to be exactly 32 bit wide on all platforms All arithmetic operations over int32 are taken modulo int zero int32 one int32 minus_one int32 gt int gt a gt int The 32 bit integers 0 1 1 neg int32 gt Unary negation add int32 gt Addition sub int32 gt Subtraction mul int32 gt Multiplication div int32 gt Integer division rem int32 gt Integer remainder If x gt 0 and y gt 0 the result of Int32 rem x y satisfies the following int32 int32 int32 int32 int32 Raise Division_by_zero if the second argument is zero int32 gt int32 gt int32 gt int32 gt int32 gt int32 properties 0 lt Int32 rem x y lt y and x Int32 add Int32 mul Int32 div x y y Int32 rem x y Ify 0 Int32 rem x y raises Division_by_zero If x lt Oor y lt 0 the
48. number of dimensions between 1 and 16 is supported The three type parameters to Genarray t identify the array element kind and layout as follows the first parameter a is the Caml type for accessing array elements float int int32 int64 nativeint the second parameter b is the actual kind of array elements float32_elt float64_elt int8_signed_elt int8_unsigned_elt etc the third parameter c identifies the array layout c_layout or fortran_layout For instance float float32_elt fortran_layout Genarray t is the type of generic big arrays containing 32 bit floats in Fortran layout reads and writes in this array use the Caml type float external create kind a b kind gt layout c layout gt dims int array gt a b c t Genarray create kind layout dimensions returns a new big array whose element kind is determined by the parameter kind one of float32 float64 int8_signed etc and whose layout is determined by the parameter layout one of c_layout or fortran_layout The dimensions parameter is an array of integers that indicate the size of the big array in each dimension The length of dimensions determines the number of dimensions of the bigarray For instance Genarray create int32 c_layout 4 6 8 returns a fresh big array of 32 bit integers in C layout having three dimensions the three dimensions being 4 6 and 8 respectively Big arrays returned by Genarray create are not i
49. src string gt dst string gt unit symlink source dest creates the file dest as a symbolic link to the file source val readlink string gt string Read the contents of a link Polling val select read file_descr list gt write file_descr list gt except file_descr list gt timeout float gt file_descr list file_descr list file_descr list Wait until some input output operations become possible on some channels The three list arguments are respectively a set of descriptors to check for reading first argument for writing second argument or for exceptional conditions third argument The fourth argument is the maximal timeout in seconds a negative fourth argument means no timeout unbounded wait The result is composed of three sets of descriptors those ready for reading first component ready for writing second component and over which an exceptional condition is pending third component 306 Locking type lock_command F_ULOCK Unlock a region F_LOCK Lock a region for writing and block if already locked F_TLOCK Lock a region for writing or fail if already locked F_TEST Test a region for other process locks F_RLOCK Lock a region for reading and block if already locked F_TRLOCK Lock a region for reading or fail if already locked Commands for lockf val lockf file_descr gt mode lock_command gt len int gt unit lockf fd cmd size puts a lock
50. string Return the given file name without its extension The extension is the shortest suffix starting with a period xyz for instance Raise Invalid_argument if the given name does not contain a period basename string gt string dirname string gt string Split a file name into directory name base file name concat dirname name basename name returns a file name which is equivalent to name Moreover after setting the current directory to dirname name with Sys chdir references to basename name which is a relative file name designate the same file as name before the call to Sys chdir temp_file prefix string gt suffix string gt string temp_file prefix suffix returns the name of a non existent temporary file in the temporary directory The base name of the temporary file is formed by concatenating prefix then a suitably chosen integer number then suffix Under Unix the temporary directory is tmp by default if set the value of the environment variable TMPDIR is used instead Under Windows the name of the temporary directory is the value of the environment variable TEMP or C temp by default Under MacOS the name of the temporary directory is given by the environment variable TempFolder if not set temporary files are created in the current directory quote string gt string Return a quoted version of a file name suitable for use as one argument in a shell command line escaping any shell meta ch
51. val cyan color val magenta color Some predefined colors val background color val foreground color Default background and foreground colors usually either black foreground on a white background or white foreground on a black background clear_graph fills the screen with the background color The initial drawing color is foreground 342 Point and line drawing val val val val val val val val val val val plot x int gt y int gt unit Plot the given point with the current drawing color point_color x int gt y int gt color Return the color of the given point in the backing store see Double buffering below moveto x int gt y int gt unit Position the current point rmoveto dx int gt dy int gt unit rmoveto dx dy translates the current point by the given vector current_x unit gt int Return the abscissa of the current point current_y unit gt int Return the ordinate of the current point current_point unit gt int int Return the position of the current point lineto x int gt y int gt unit Draw a line with endpoints the current point and the given point and move the current point to the given point rlineto dx int gt dy int gt unit Draws a line with endpoints the current point and the current point translated by the given vector and move the current point to this point draw_rect x int gt y int gt w int
52. value val pause unit gt unit Wait until a non ignored non blocked signal is delivered Chapter 20 The unix library Unix system calls 307 Time functions type process_times tms_utime float User time for the process tms_stime float System time for the process tms_cutime float User time for the children processes tms_cstime float System time for the children processes The execution times CPU times of a process type tm tm_sec int Seconds 0 59 tm_min int Minutes 0 59 tm_hour int Hours 0 23 tm_mday int Day of month 1 31 tm_mon int Month of year 0 11 tm_year int Year 1900 tm_wday int Day of week Sunday is 0 tm_yday int Day of year 0 365 tm_isdst bool Daylight time savings in effect val val val val val val The type representing wallclock time and calendar date time unit gt float Return the current time since 00 00 00 GMT Jan 1 1970 in seconds gettimeofday unit gt float Same as time but with resolution better than 1 second gmtime float gt tm Convert a time in seconds as returned by time into a date and a time Assumes Greenwich meridian time zone also known as UTC localtime float gt tm Convert a time in seconds as returned by time into a date and a time Assumes the local time zone mktime tm gt float tm Conver
53. x notify self e observers end class a b subject object c constraint a lt notify c gt b gt unit gt val mutable observers a list 80 method add_observer a gt unit method notify_observers b gt unit end The difficulty usually relies in defining instances of the pattern above by inheritance This can be done in a natural and obvious manner in Ocaml as shown on the following example manipulating windows type event Raise Resize Move type event Raise Resize Move let string_of_event function Raise gt Raise Resize gt Resize Move gt Move val string _of_event event gt string lt fun gt let count ref 0 val count int ref f contents 0 class observer window_subject let id count succ count count in object self inherit observer event subject val mutable position 0 method identity id method move x position lt position x self notify_observers Move method draw Printf printf Position d n position end class a window_subject object b constraint a lt notify b gt event gt unit gt val mutable observers a list val mutable position int method add_observer a gt unit method draw unit method identity int method move int gt unit method notify_observers event gt unit end cl
54. 2 int 1 head Uncaught exception Empty_list Exceptions are used throughout the standard library to signal cases where the library functions cannot complete normally For instance the List assoc function which returns the data associ ated with a given key in a list of key data pairs raises the predefined exception Not_found when the key does not appear in the list List assoc 1 0 zero 1 one string one List assoc 2 0 zero 1 one Uncaught exception Not_found Exceptions can be trapped with the try with construct let name_of_binary_digit digit try List assoc digit 0 zero 1 one with Not_found gt not a binary digit val name_of_binary_digit int gt string lt fun gt name_of_binary_digit 0 string zero name_of_binary_digit 1 string not a binary digit The with part is actually a regular pattern matching on the exception value Thus several exceptions can be caught by one try with construct Also finalization can be performed by trapping all exceptions performing the finalization then raising again the exception let temporarily_set_reference ref newval funct let oldval ref in try ref newval let res funct in ref oldval res with x gt ref oldval raise x val temporarily_set_reference a ref gt a gt unit gt b g
55. 265 277 pred_num 321 prerr_char 231 prerr_endline 231 prerr_float 231 prerr_int 231 prerr_newline 231 prerr_string 231 print 280 print_as 248 print_bool 248 print_break 248 print_char 230 248 print_cut 248 print_endline 230 print_float 230 248 print_flush 249 print_if_newline 249 print_int 230 248 382 print_newline 230 249 print_space 248 print_stat 258 print_string 230 248 print_tab 250 print_tbreak 250 Printexc module 280 printf 255 281 Printf module 280 push 286 putenv 298 Queue module 282 quo_num 320 quote 246 326 raise 222 raise_window 354 Random module 283 ratio_of_num 322 rcontains_from 290 read 300 337 read_float 231 read_int 231 read_key 345 read_line 231 readdir 304 readlink 305 really_input 234 receive 335 recv 312 338 recvfrom 312 338 red 341 ref 236 regexp 325 regexp_case_fold 326 regexp_string 326 regexp_string_case_fold 326 register 244 register_exception 244 rem 262 265 277 remember_mode 346 remove 260 291 348 remove_assoc 272 remove_assq 272 rename 291 302 replace 348 replace_first 327 replace_matched 328 reset 243 rev 269 rev_append 270 rev_map 270 rev_map2 271 rewinddir 304 rgb 341 rhs_end 280 rhs_start 280 rindex 290 rindex_from 290 rlineto 342 rmdir 303 rmoveto 342 round_num 320 search_backward 326 search_forward 326 seek_in 235 seek_out 233 s
56. 3 unit pH get_x int 3 35 36 The evaluation of the body of a class only takes place at object creation time Therefore in the following example the instance variable x is initialized to different values for two different objects let xO ref 0 val x0 int ref contents 0 class point object val mutable x incr x0 x0 method get_x x method move d x lt x d end class point object val mutable x int method get_x int method move int gt unit end HH new point get_x int 1 new point get_x int 2 The class point can also be abstracted over the initial values of points class point fun x_init gt object val mutable x x_init method get_x x method move d x lt x d end class point int gt object val mutable x int method get_x int method move int gt unit end As for declaration of functions the above definition can be abbreviated as class point x_init object val mutable x x_init method get_x x method move d x lt x d end class point int gt object val mutable x int method get_x int method move int gt unit end An instance of the class point is now a function that expects an initial parameter to create a point object new point int gt point lt fun gt let p new point 7 val p point lt obj gt Chapter 3 Objects in Caml 3
57. 6 The Objective Caml language 97 Patterns are linear a variable cannot appear several times in a given pattern In particular there is no way to test for equality between two parts of a data structure using only a pattern but when guards can be used for this purpose Constant patterns A pattern consisting in a constant matches the values that are equal to this constant Alias patterns The pattern pattern as value name matches the same values as pattern If the matching against pattern is successful the name name is bound to the matched value in addition to the bindings performed by the matching against pattern Parenthesized patterns The pattern pattern matches the same values as pattern A type constraint can appear in a parenthesized pattern as in pattern typexpr This constraint forces the type of pattern to be compatible with type Or patterns The pattern pattern pattern represents the logical or of the two patterns pattern and pattern A value matches pattern patterns either if it matches pattern or if it matches patterns The two sub patterns pattern and pattern must contain no identifiers Hence no bindings are returned by matching against an or pattern Variant patterns The pattern ncconstr pattern matches all variants whose constructor is equal to ncconstr and whose argument matches pattern The pattern pattern pattern matches non empty lists whose heads match
58. 6 8 1 6 5 Constants 96 constant integer literal float literal char literal string literal cconstr lt tag name The syntactic class of constants comprises literals from the four base types integers floating point numbers characters character strings and constant constructors from both normal and polymorphic variants 6 6 Patterns pattern value name constant pattern as value name pattern pattern typexpr pattern pattern nceconstr pattern tag name pattern typeconstr name pattern pattern field pattern field pattern pattern pattern pattern pattern The table below shows the relative precedences and associativity of operators and non closed pattern constructions The constructions with higher precedences come first Operator Associativity Constructor application right l left as Patterns are templates that allow selecting data structures of a given shape and binding iden tifiers to components of the data structure This selection operation is called pattern matching its outcome is either this value does not match this pattern or this value matches this pattern resulting in the following bindings of names to values Variable patterns A pattern that consists in a value name matches any value binding the name to the value The pattern _ also matches any value but does not bind any name Chapter
59. Caml Light standard library to produce a standalone executable program The order in which cmo and ml arguments are presented on the command line is relevant compilation units are initialized in that order at run time and it is a link time error to use a component of a unit before having initialized it Hence a given x cmo file must come before all cmo files that refer to the unit z 131 132 e Arguments ending in cma are taken to be libraries of object bytecode A library of object bytecode packs in a single file a set of object bytecode files cmo files Libraries are built with ocamlc a see the description of the a option below The object files contained in the library are linked as regular cmo files see above in the order specified when the cma file was built The only difference is that if an object file contained in a library is not referenced anywhere in the program then it is not linked in e Arguments ending in c are passed to the C compiler which generates a o object file This object file is linked with the program if the custom flag is set see the description of custom below e Arguments ending in o or a are assumed to be C object files and libraries They are passed to the C linker when linking in custom mode see the description of custom below The output of the linking phase is a file containing compiled bytecode that can be executed by the Objective Caml bytecode interpreter the command named oc
60. It declares the functions constants and macros discussed below 28 2 2 Accessing a Caml bigarray from C or Fortran If v is a Caml value representing a big array the expression Data_bigarray_val v returns a pointer to the data part of the array This pointer is of type void and can be cast to the appropriate C type for the array e g double char 10 etc Various characteristics of the Caml big array can be consulted from C as follows C expression Returns Bigarray_val v gt num_dims number of dimensions Bigarray_val v gt dim i il i th dimension Bigarray_val v gt flags amp BIGARRAY_KIND_MASK kind of array elements The kind of array elements is one of the following constants 370 Constant Element kind BIGARRAY_FLOAT32 32 bit single precision floats BIGARRAY_FLOAT64 64 bit double precision floats BIGARRAY_SINT8 8 bit signed integers BIGARRAY_UINTS 8 bit unsigned integers BIGARRAY_SINT16 16 bit signed integers BIGARRAY_UINT16 16 bit unsigned integers BIGARRAY_INT32 32 bit signed integers BIGARRAY_INT64 64 bit signed integers BIGARRAY_CAML_INT 31 or 63 bit signed integers BIGARRAY_NATIVE_INT 32 or 64 bit platform native integers The following example shows the passing of a two dimensional big array to a C function and a Fortran function extern void my_c_function double data int dimx int dimy extern void my_fortran_function_ double data int dimx int dimy
61. Module Stream streams and parsers type at The type of streams holding values of type a exception Failure Raised by parsers when none of the first components of the stream patterns is accepted exception Error of string Raised by parsers when the first component of a stream pattern is accepted but one of the following components is rejected Stream builders Warning these functions create streams with fast access it is illegal to mix them with streams built with lt gt would raise Failure when accessing such mixed streams val from int gt a option gt a t Stream from f returns a stream built from the function f To create a new stream element the function f is called with the current stream count The user function f must return either Some lt value gt for a value or None to specify the end of the stream val of_list a list gt at Return the stream holding the elements of the list in the same order val of_string string gt char t Return the stream of the characters of the string parameter val of_channel in_channel gt char t Return the stream of the characters read from the input channel 288 Stream iterator val iter f a gt unit gt a t gt unit Stream iter f s scans the whole stream s applying function f in turn to each stream element encountered Predefined parsers val next at gt a Return the first element of the stream a
62. None Some of a The type of optional values Ca b c format The type of format strings a is the type of the parameters of the format c is the result type for the printf style function and b is the type of the first argument given to a and t printing functions see module Printf Exceptions val raise exn gt a exception Match_failure of string int int Raise the given exception value Exception raised when none of the cases of a pattern matching apply The arguments are the location of the pattern matching in the source code file name position of first character position of last character Chapter 18 The core library 223 exception Assert_failure of string int int Exception raised when an assertion fails The arguments are the location of the pattern matching in the source code file name position of first character position of last character exception Invalid_argument of string Exception raised by library functions to signal that the given arguments do not make sense exception Failure of string Exception raised by library functions to signal that they are undefined on the given arguments exception Not_found Exception raised by search functions when the desired object could not be found exception Out_of_memory Exception raised by the garbage collector when there is insufficient memory to complete the computation exception Stack_overflow Exception raised by the
63. O nand out n O 1 252 val get_all_formatter_output_functions unit gt buf string gt pos int gt len int gt unit unit gt unit unit gt unit int gt unit Return the current output functions of the pretty printer including line breaking and indentation functions Multiple formatted output type formatter val val val val val val Abstract data type corresponding to a pretty printer and all its machinery Defining new pretty printers permits the output of material in parallel on several channels Parameters of the pretty printer are local to the pretty printer margin maximum indentation limit maximum number of boxes simultaneously opened ellipsis and so on are specific to each pretty printer and may be fixed independently Given an output channel oc a new formatter writing to that channel is obtained by calling formatter_of_out_channel oc Alternatively the make_formatter function allocates a new formatter with explicit output and flushing functions convenient to output material to strings for instance formatter_of_out_channel out_channel gt formatter formatter_of_out_channel oc returns a new formatter that writes to the corresponding channel oc std_formatter formatter The standard formatter used by the formatting functions above It is defined as formatter_of_out_channel stdout err_formatter formatter A formatter to use with formatting functio
64. TIMES l DIV EEG LPAREN Ie 298 RPAREN eof raise Eof Here is the main program that combines the parser with the lexer File calc ml let _ try let lexbuf Lexing from_channel stdin in while true do let result Parser main Lexer token lexbuf in print_int result print_newline flush stdout done with Lexer Eof gt exit 0 To compile everything execute ocamllex lexer mll generates lexer ml ocamlyacc parser mly generates parser ml and parser mli ocamlc c parser mli ocamlc c lexer ml ocamlc c parser ml ocamlc c calc ml ocamlc o calc lexer cmo parser cmo calc cmo 12 7 Common errors ocamllex transition table overflow automaton is too big The deterministic automata generated by ocamllex are limited to at most 32767 transitions The message above indicates that your lexer definition is too complex and overflows this limit This is commonly caused by lexer definitions that have separate rules for each of the alphabetic keywords of the language as in the following example rule token parse keywordi KWD1 keyword2 KWD2 keyword100 KWD100 A Z 1a Zz PA Z 2a 2 z 20 3a IDENT Lexing lexeme lexbuf Chapter 12 Lexer and parser generators ocamllex ocamlyacc 165 To keep the generated automata small rewrite those definitions with only one general iden tifier rule followed by a hashtable lookup to separate keywords fro
65. The toplevel system does not perform line editing but it can easily be used in conjunction with an external line editor such as fep just run fep emacs ocaml or fep vi ocaml Another option is to use ocaml under Gnu Emacs which gives the full editing power of Emacs see the subdirectory emacs of the Objective Caml distribution At any point the parsing compilation or evaluation of the current phrase can be interrupted by pressing ctr1 C or more precisely by sending the sigintr signal to the ocam1 process The toplevel then immediately returns to the prompt If a filename is given on the command line to ocam1 the toplevel system enters script mode the contents of the file are read as a sequence of Objective Caml phrases and executed as per the use directive section 9 2 The outcome of the evaluation is not printed On reaching the end of file the ocaml command exits immediately No commands are read from standard input Sys argv is transformed ignoring all Objective Caml parameters and starting with the script file name in Sys argv 0 In script mode the first line of the script is ignored if it starts with Thus it is theoretically possible to make the script itself executable and put as first line usr local bin ocaml thus calling the toplevel system automatically when the script is run However ocam1 itself is a script on most installations of Objective Caml and Unix kernels usually do not handle nested scripts
66. a amp Be 2 Bw ee eek eed oo aa E E al eae Geshe 2s Multiple inheritance 2 ee Parameterized classes oant ss ou fees A pe pa eo ep Ae ee nO eg Using COCTCIONS Sor eet bsn Shona A eee eek Re See PE hae oO Ged Functional Objects m esri ie es Be ee ee ke ee Bed Cloning objects aia 60 BoP ao ae ete Boe Rae oe ee oe Re Be ee Bad Recursive classes 0 2 ie 8 Sa ba es be Ge FA a e a Binary methods 2 4 a uce 25 02 se a P44 Ree ba he eek ee e aa BIOTIC Ss tn octet dose Gc ace be che BAe eke Mates Saat Specie Meher S ate Grae Geol aed Roi ai i work at 11 11 12 13 14 16 17 19 20 22 25 25 31 4 The module system 4 1 4 2 4 3 4 4 4 5 DUPUCUULCS acs geag a i e e ds Soy Stee Bree a haste ae ee shee Sea coe Jeet See Ces DlSnatUTes ta ee kaea O Ree ee ak eae eee a ew OE Oars se ee PUNCO airy tlc gh Oh ey Ge ae we es Ae IE gh a Pe lth woe he al eee NOB Mod Buus Functors and type abstraction o oo ee Modules and separate compilation s o aa ee 5 Advanced examples with classes and modules 5 1 5 2 5 3 Extended example bank accounts ooo a Simple modules as classes o oo a The subject observer pattern 244 5526 544 07 a II The Objective Caml language 6 The Objective Caml language 6 1 6 2 6 3 6 4 6 5 6 6 6 7 6 8 6 9 6 10 6 11 6 12 Lexical Con VentiOns iran e n ain nen a Ee eS Be a ee E E Values iie oA Ge eee Ae en Ee ee a ee oe NAMES 55 tee ag Yi Re i nal oS eee ld te Sed oe Ge
67. a compiled bytecode file cmo file If filename has the format mod cmi this means you are trying to compile a file that references identifiers from module mod but you have not yet compiled an interface for module mod Fix compile mod mli or mod ml first to create the compiled interface mod cmi If filename has the format mod cmo this means you are trying to link a bytecode object file that does not exist yet Fix compile mod m1 first If your program spans several directories this error can also appear because you haven t specified the directories to look into Fix add the correct I options to the command line Corrupted compiled interface filename This The compiler produces this error when it tries to read a compiled interface file cmi file that has the wrong structure This means something went wrong when this cmi file was written the disk was full the compiler was interrupted in the middle of the file creation and so on This error can also appear if a cmi file is modified after its creation by the compiler Fix remove the corrupted cmi file and rebuild it expression has type t but is used with type tz This is by far the most common type error in programs Type t is the type inferred for the expression the part of the program that is displayed in the error message by looking at the expression itself Type tz is the type expected by the context of the expression it is deduced by looking at how the value of
68. a definition similar to those found in implementations of compilation units or in struct end module expressions The definition can bind value names type names an exception a module name or a module type name The toplevel system performs the bindings then prints the types and values if any for the names thus defined A phrase may also consist in a open directive see section 6 11 or a value expression sec tion 6 7 Expressions are simply evaluated without performing any bindings and the value of the expression is printed 139 140 Finally a phrase can also consist in a toplevel directive starting with the sharp sign These directives control the behavior of the toplevel they are listed below in section 9 2 Unix The toplevel system is started by the command ocam1 as follows ocaml options interactive mode ocaml options scriptfile script mode If no filename is given on the command line the toplevel system enters interactive mode phrases are read on standard input results are printed on standard output errors on stan dard error End of file on standard input terminates ocaml see also the quit directive in section 9 2 On start up before the first phrase is read if the file ocamlinit exists in the current directory its contents are read as a sequence of Objective Caml phrases and executed as per the use directive described in section 9 2 The evaluation outcode for each phrase are not displayed
69. a mutex The typical use is if D is a shared data structure m its mutex and c is a condition variable Mutex lock m while some predicate P over D is not satisfied do Condition wait c m done Modify D if the predicate P over D is now satified then Condition signal c Mutex unlock m Chapter 23 The threads library 335 type t The type of condition variables val create unit gt t Return a new condition variable val wait t gt locking Mutex t gt unit wait c m atomically unlocks the mutex m and suspends the calling process on the condition variable c The process will restart after the condition variable c has been signalled The mutex m is locked again before wait returns val signal t gt unit signal c restarts one of the processes waiting on the condition variable c val broadcast t gt unit broadcast c restarts all processes waiting on the condition variable c 23 4 Module Event first class synchronous communication This module implements synchronous inter thread communications over channels As in John Reppy s Concurrent ML system the communication events are first class values they can be built and combined independently before being offered for communication type a channel The type of communication channels carrying values of type a val new_channel unit gt a channel Return a new channel type a event The type of communication events returning a result of type
70. a similar It can only be defined by a class or a classtyped definition One reason is that sharp abbreviations carry an implicit anonymous variable that cannot be explicitly named Thus the abbreviation c0 should be expanded class c object self method m self lt m c1 gt as a gt cl end Already bound type parameter a 3 11 Functional objects It is possible to write a version of class point without assignments on the instance variables The construct lt gt returns a copy of self that is the current object possibly changing the value of some instance variables class functional_point y object val x y method get_x x method move d lt x x d gt end class functional_point int gt object a val x int method get_x int method move int gt a end let p new functional_point 7 val p functional_point lt obj gt Chapter 3 Objects in Caml 51 p get_x int SF p move 3 get_x int 10 p get_x int 7 Note that the type abbreviation functional_point is recursive which can be seen in the class type of functional_point the type of self is a and a appears inside the type of the method move The above definition of functional_point is not equivalent to the following class bad_functional_point y object val x y method get_x x method move d new functional_point x d end cla
71. abstract type of buffers create int gt t create nreturns a fresh buffer initially empty The n parameter is the initial size of the internal string that holds the buffer contents That string is automatically reallocated when more than n characters are stored in the buffer but shrinks back to n characters when reset is called For best performance n should be of the same order of magnitude as the number of characters that are expected to be stored in the buffer for instance 80 for a buffer that holds one output line Nothing bad will happen if the buffer grows beyond that limit however In doubt take n 16 for instance If n is not between 1 and Sys max_string_length it will be clipped to that interval contents t gt string Return a copy of the current contents of the buffer The buffer itself is unchanged length t gt int Return the number of characters currently contained in the buffer clear t gt unit Empty the buffer reset t gt unit Empty the buffer and deallocate the internal string holding the buffer contents replacing it with the initial internal string of length n that was allocated by create n For long lived buffers that may have grown a lot reset allows faster reclaimation of the space used by the buffer add_char t gt char gt unit add_char b c appends the character c at the end of the buffer b add_string t gt string gt unit add_string b s appends the string s at the end
72. actual value of the type parameter is displayed in the constraint clause class a ref_succ x_init a object val mutable x x_init 1 46 method get x method set y x lt y end class a ref_succ 2a gt object constraint a int val mutable x int method get int method set int gt unit end Let us consider a more realistic example We put an additional type constraint in method move since no free variables must remain uncaptured by a type parameter class a circle c a object val mutable center c method center center method set_center c center lt c method move center move int gt unit end class a circle 2a gt object constraint a lt move int gt unit gt val mutable center a method center a method move int gt unit method set_center a gt unit end An alternate definition of circle using a constraint clause in the class definition is shown below The type point used below in the constraint clause is an abbreviation produced by the definition of class point This abbreviation unifies with the type of any object belonging to a subclass of class point It actually expands to lt get_x int move int gt unit gt This leads to the following alternate definition of circle which has slightly stronger constraints on its argument as we now expect center to have a method
73. between sets Can be used as the ordering function for doing sets of sets val equal t gt t gt bool equal s1 s2 tests whether the sets s1 and s2 are equal that is contain equal elements val subset t gt t gt bool subset s1 s2 tests whether the set s1 is a subset of the set s2 Chapter 19 The standard library 285 val iter f elt gt unit gt t gt unit iter f s applies f in turn to all elements of s The order in which the elements of s are presented to f is unspecified val fold f elt gt a gt a gt t gt init a gt a fold f s a computes f xN f x2 f x1 a where x1 xN are the elements of s The order in which elements of s are presented to f is unspecified val for_all f elt gt bool gt t gt bool for_all p s checks if all elements of the set satisfy the predicate p val exists f elt gt bool gt t gt bool exists p s checks if at least one element of the set satisfies the predicate p val filter f elt gt bool gt t gt t filter p s returns the set of all elements in s that satisfy predicate p val partition f elt gt bool gt t gt t t partition p s returns a pair of sets s1 s2 where s1 is the set of all the elements of s that satisfy the predicate p and s2 is the set of all the elements of s that do not satisfy p val cardinal t gt int Return the number of elements of a set val elements t gt elt list Return
74. by fmt fmt is a Printf style format containing exactly one 4d i u X X or ho conversion specification See the documentation of the Printf module for more information 19 20 Module Oo object oriented extension val copy lt gt as a gt a Oo copy o returns a copy of object o that is a fresh object with the same methods and instance variables as o 19 21 Module Parsing the run time library for parsers generated by ocamlyacc val symbol_start unit gt int val symbol_end unit gt int symbol_start and symbol_end are to be called in the action part of a grammar rule only They return the position of the string that matches the left hand side of the rule symbol_start returns the position of the first character symbol_end returns the position of the last character plus one The first character in a file is at position 0 280 val rhs_start int gt int val rhs_end int gt int Same as symbol_start and symbol_end but return the position of the string matching the nth item on the right hand side of the rule where n is the integer parameter to lhs_start and lhs_end n is 1 for the leftmost item val clear_parser unit gt unit Empty the parser stack Call it just after a parsing function has returned to remove all pointers from the parser stack to structures that were built by semantic actions during parsing This is optional but lowers the memory requirements of the programs exception Pa
75. checks that class type match the type of class expr that is that the implementation class expr meets the type specification class type The whole expression evaluates to the same class as class expr except that all components not specified in class type are hidden and can no longer be accessed Class application Class application is denoted by juxtaposition of possibly labeled expressions Evaluation works as for expression application Class function The expression fun label pattern gt class expr evaluates to a function from values to classes When this function is applied to a value v this value is matched against the pattern pattern and the result is the result of the evaluation of class expr in the extended environment Conversion from functions with default values to functions with patterns only works identically for class functions as for normal functions The expression fun parameter parameter gt class expr is a short form for fun parameter gt fun parameter gt expr Chapter 6 The Objective Caml language 115 Local definitions The let and let rec constructs bind value names locally as for the core language expressions Class body The expression object pattern typexpr class field end denotes a class body This is the prototype for an object it lists the instance variables and methods of an objet of this class A class body is a class value it is not evaluated at once Rather
76. code of the Caml program Typically this initialization code registers callback functions using Callback register Once the Caml initialization code is complete control returns to the C code that called caml_main e The C code can then invoke Caml functions using the callback mechanism see section 17 7 1 17 7 5 Embedding the Caml code in the C code The bytecode compiler in custom runtime mode ocamlc custom normally appends the bytecode to the executable file containing the custom runtime This has two consequences First the final linking step must be performed by ocamlc Second the Caml runtime library must be able to find the name of the executable file from the command line arguments When using caml_main argv as in section 17 7 4 this means that argv 0 or argv 1 must contain the executable file name An alternative is to embed the bytecode in the C code The output obj option to ocamlc is provided for this purpose It causes the ocamlc compiler to output a C object file o file containing the bytecode for the Caml part of the program as well as a caml_startup function 212 The C object file produced by ocamlc output obj can then be linked with C code using the standard C compiler or stored in a C library The caml_startup function must be called from the main C program in order to initialize the Caml runtime and execute the Caml initialization code Just like caml_main it takes one argv parameter containing the command
77. connect Unix file_descr gt Unix sockaddr gt unit recv Unix file_descr gt buf string gt pos int gt len int gt mode Unix msg_flag list gt int recvfrom Unix file_descr gt buf string gt pos int gt len int gt mode Unix msg_flag list gt int Unix sockaddr send Unix file_descr gt buf string gt pos int gt len int gt mode Unix msg_ flag list gt int sendto Unix file_descr gt buf string gt pos int gt len int gt mode Unix msg_flag list gt addr Unix sockaddr gt int open_connection Unix sockaddr gt in_channel out_channel establish_server in_channel gt out_channel gt a gt addr Unix sockaddr gt unit Chapter 24 The graphics library The graphics library provides a set of portable drawing primitives Drawing takes place in a separate window that is created when open_graph is called Unix This library is implemented under the X11 windows system Programs that use the graphics library must be linked as follows ocamlc other options graphics cma other files For interactive use of the graphics library do ocamlmktop o mytop graphics cma mytop Here are the graphics mode specifications supported by open_graph on the X11 implementa tion of this library the argument to open_graph has the format display name geometry where display name is the name of the X windows display to connect to and geometry is a standard X windows geometry specification T
78. correct directories to the search path 144 This expression has type t but is used with type t2 See section 8 4 Reference to undefined global mod You have neglected to load in memory an implementation for a module with load See section 9 3 above 9 5 Building custom toplevel systems ocamlmktop The ocamlmktop command builds Objective Caml toplevels that contain user code preloaded at start up The ocamlmktop command takes as argument a set of cmo and cma files and links them with the object files that implement the Objective Caml toplevel The typical use is ocamlmktop o mytoplevel foo cmo bar cmo gee cmo This creates the bytecode file mytoplevel containing the Objective Caml toplevel system plus the code from the three cmo files This toplevel is directly executable and is started by mytoplevel This enters a regular toplevel loop except that the code from foo cmo bar cmo and gee cmo is already loaded in memory just as if you had typed load foo cmo load bar cmo load gee cmo on entrance to the toplevel The modules Foo Bar and Gee are not opened though you still have to do open Foo yourself if this is what you wish 9 6 Options The following command line options are recognized by ocamlmktop cclib ltbname Pass the lLlibname option to the C linker when linking in custom runtime mode See the corresponding option for ocamlc in chapter 8 ccopt option Pass the give
79. digest file string gt t Return the digest of the file whose name is given output out_channel gt t gt unit Write a digest on the given output channel input in_channel gt t Read a digest from the given input channel 19 7 Module Filename operations on file names val val val current_dir_name string The conventional name for the current directory e g in Unix parent_dir_name string The conventional name for the parent of the current directory e g in Unix concat string gt string gt string concat dir file returns a file name that designates file file in directory dir 246 val val val val val val val val val is_relative string gt bool Return true if the file name is relative to the current directory false if it is absolute i e in Unix starts with is_implicit string gt bool Return true if the file name is relative and does not start with an explicit reference to the current directory or in Unix false if it starts with an explicit reference to the root directory or the current directory check_suffix string gt string gt bool check_suffix name suff returns true if the filename name ends with the suffix suff chop_suffix string gt string gt string chop_suffix name suff removes the suffix suff from the filename name The behavior is undefined if name does not end with the suffix suff chop_extension string gt
80. disable all warnings F f enable disable warnings for partially applied functions i e f x expr where the appli cation f x has a function type M m enable disable warnings for overriden methods P p enable disable warnings for partial matches missing cases in pattern matchings S s enable disable warnings for statements that do not have type unit e g expri expr when ezpr1 does not have type unit U u enable disable warnings for unused redundant match cases V v enable disable warnings for hidden instance variables X x enable disable all other warnings The default setting is w A all warnings enabled 8 3 Modules and the file system This short section is intended to clarify the relationship between the names of the modules corre sponding to compilation units and the names of the files that contain their compiled interface and compiled implementation The compiler always derives the module name by taking the capitalized base name of the source file ml or mli file That is it strips the leading directory name if any as well as the m1 or mli suffix then it set the first letter to uppercase in order to comply with the requirement that module names must be capitalized For instance compiling the file mylib misc ml provides an implementation for the module named Misc Other compilation units may refer to components defined in mylib misc ml under the names Misc name they can also do open Misc then use unqualified
81. executed set loadingmode direct The program is run directly by the debugger This is the default mode Chapter 15 The debugger ocamldebug 183 set loadingmode runtime The debugger execute the Objective Caml runtime camlrun on the program Rarely useful moreover it prevents the debugging of programs compiled in custom runtime mode set loadingmode manual The user starts manually the program when asked by the debugger Allows remote debugging see section 15 8 6 15 8 3 Search path for files The debugger searches for source files and compiled interface files in a list of directories the search path The search path initially contains the current directory and the standard library directory The directory command adds directories to the path Whenever the search path is modified the debugger will clear any information it may have cached about the files directory directorynames Add the given directories to the search path These directories are added at the front and will therefore be searched first directory Reset the search path This requires confirmation 15 8 4 Working directory Each time a program is started in the debugger it inherits its working directory from the current working directory of the debugger This working directory is initially whatever it inherited from its parent process typically the shell but you can specify a new working directory in the debugger with the cd command or the cd command
82. execution Printing profiling information Time profiling 4 17 Interfacing C with Objective Caml 17 1 17 2 17 3 17 4 17 5 17 6 17 7 17 8 17 9 Overview and compilation information The value type 04 Representation of Caml data types Operations on values 2058 Living in harmony with the garbage collector A complete example Advanced topic callbacks from C to Caml Advanced example with callbacks Advanced topic custom blocks IV The Objective Caml library 18 The core library 18 1 Module Pervasives the initially opened module 19 The standard library 19 1 19 2 19 3 19 4 19 5 19 6 19 7 19 8 19 9 19 10 19 11 19 12 19 13 19 14 19 15 19 16 19 17 Module Arg parsing of command line arguments Module Array array operations Module Buffer extensible string buffers Module Char character operations Module Digest MD5 message digest Module Filename operations on filenames Module Format pretty printing Module Genlex a generic lexical analyzer Module Hashtb1 hash tables and hash functions Module Int32 32 bit integers Module Int64 64 bit integers Module Lazy deferred computations Module List list operations Module Map association tables over ordered types Modu
83. floating point number then the maximum size is only Sys max_array_length 2 Array create_matrix is a deprecated alias for Array make_matrix append a array gt a array gt a arra PP y Array append v1 v2 returns a fresh array containing the concatenation of the arrays v1 and v2 concat a array list gt a array Same as Array append but catenates a list of arrays sub a array gt pos int gt len int gt a array Array sub a start len returns a fresh array of length len containing the elements number start to start len 1 of array a Raise Invalid_argument Array sub if start and len do not designate a valid subarray of a that is if start lt 0 or len lt 0 or start len gt Array length a copy a array gt a array Array copy a returns a copy of a that is a fresh array containing the same elements as a fill a array gt pos int gt len int gt a gt unit Array fill a ofs len x modifies the array a in place storing x in elements number ofs to ofs len 1 Raise Invalid_argument Array fill if ofs and len do not designate a valid subarray of a blit src a array gt src_pos int gt dst a array gt dst_pos int gt len int gt unit Array blit v1 o1 v2 02 len copies len elements from array v1 starting at element number o1 to array v2 starting at element number o2 It works correctly even if vi and v2 are the same array and the source and desti
84. if the data contained in the two blocks are structurally equal a negative integer if the data from the first block is less than the data from the second block Chapter 17 Interfacing C with Objective Caml 215 and a positive integer if the data from the first block is greater than the data from the second block The compare field can be set to custom_serialize_default this default comparison func tion simply raises Failure e long hash value v The hash field contains a pointer to a C function that is called whenever Caml s generic hash operator see module Hashtb1 is applied to a custom block The C function can return an arbitrary long integer representing the hash value of the data contained in the given custom block The hash value must be compatible with the compare function in the sense that two structurally equal data that is two custom blocks for which compare returns 0 must have the same hash value The hash field can be set to custom_hash_default in which case the custom block is ignored during hash computation e void serialize value v unsigned long wsize_32 unsigned long wsize_64 The serialize field contains a pointer to a C function that is called whenever the cus tom block needs to be serialized marshaled using the Caml functions output_value or Marshal to_ For a custom block those functions first write the identifier of the block as given by the identifier field to the output stream then call
85. if your function is a primitive with more than 5 arguments for use with the byte code runtime its arguments are not values and must not be declared they have types value and int Rule 2 Local variables of type value must be declared with one of the CAMLlocal macros Arrays of values are declared with CAMLlocalN The macros CAMLlocali to CAMLlocal5 declare and initialize one to five local variables of type value The variable names are given as arguments to the macros CAMLlocalN z n declares and initializes a local variable of type value n You can use several calls to these macros if you have more than 5 local variables You can also use them in nested C blocks within the function Example value bar value vi value v2 value v3 CAMLparam3 v1 v2 v3 CAMLlocall result result alloc 3 0 CAMLreturn result Rule 3 Assignments to the fields of structured blocks must be done with the Store_field macro Other assignments must not use Store_field Chapter 17 Interfacing C with Objective Caml 205 Store_field b n v stores the value v in the field number n of value b which must be a block i e Is_block b must be true Example value bar value vi value v2 value v3 CAMLparam3 v1 v2 v3 CAMLlocali result result alloc 3 0 Store_field result 0 v1 Store_field result 1 v2 Store_field result 2 v3 CAMLreturn result Rule 4 Global variables containing values must be
86. include The modtype path argument must refer to a module type that is a signature Chapter 6 The Objective Caml language 121 6 10 3 Functor types The module type expression functor module name module type gt module type is the type of functors functions from modules to modules that take as argument a module of type module type and return as result a module of type module type The module type module type can use the name module name to refer to type components of the actual argument of the functor No restrictions are placed on the type of the functor argument in particular a functor may take another functor as argument higher order functor 6 10 4 The with operator Assuming module type denotes a signature the expression module type with mod constraint and mod constr denotes the same signature where type equations have been added to some of the type spec ifications as described by the constraints following the with keyword The constraint type type parameters typeconstr typexp adds the type equation typexp to the specification of the type component named typeconstr of the constrained signature The constraint module module path extended module path adds type equations to all type components of the sub structure denoted by module path making them equivalent to the corresponding type components of the structure denoted by extended module path For instance if the module type name is bound to the s
87. is fully supported not implemented use threads not implemented Chapter 21 The num library arbitrary precision rational arithmetic The num library implements exact precision rational arithmetic It is built upon the state of the art BigNum arbitrary precision integer arithmetic package and therefore achieves very high performance The functions provided in this library are fully documented in The CAML Numbers Reference Manual by Val rie M nissier Morain technical report 141 INRIA july 1992 available electron ically ftp ftp inria fr INRIA publication RT RT 0141 ps gz A summary of the func tions is given below Programs that use the num library must be linked as follows ocamlc other options nums cma other files ocamlopt other options nums cmxa other files For interactive use of the nums library do ocamlmktop o mytop nums cma mytop 21 1 Module Num operation on arbitrary precision numbers open Nat open Big_int open Ratio Numbers type num are arbitrary precision rational numbers plus the special elements 1 0 infinity and 0 0 undefined type num Int of int Big_int of big_int Ratio of ratio The type of numbers Arithmetic operations 319 320 val num gt num gt num val add_num num gt num gt num Addition val minus_num num gt num Unary negation val num gt num gt num val sub_num num gt num gt num Subtraction val n
88. is unreachable ENETRESET Network dropped connection on reset ECONNABORTED Software caused connection abort ECONNRESET Connection reset by peer ENOBUFS No buffer space available EISCONN Socket is already connected ENOTCONN Socket is not connected ESHUTDOWN Can t send after socket shutdown ETOOMANYREFS Too many references can t splice ETIMEDOUT Connection timed out ECONNREFUSED Connection refused EHOSTDOWN Host is down EHOSTUNREACH No route to host ELOOP Too many levels of symbolic links All other errors are mapped to EUNKNOWNERR EUNKNOWNERR of int Unknown error The type of error codes exception Unix_error of error string string Raised by the system calls below when an error is encountered The first component is the error code the second component is the function name the third component is the string parameter to the function if it has one or the empty string otherwise val error_message error gt string Return a string describing the given error code val handle_unix_error a gt b gt a gt b handle_unix_error f x applies f to x and returns the result If the exception Unix_error is raised it prints a message describing the error and exits with code 2 298 Access to the process environment val environment unit gt string array Return the process environment as an ar
89. itself For instance here are functions performing lookup and insertion in ordered binary trees elements increase from left to right let rec member x btree match btree with Empty gt false Node y left right gt if x y then true else if x lt y then member x left else member x right val member a gt a btree gt bool lt fun gt let rec insert x btree match btree with Empty gt Node x Empty Empty Node y left right gt if x lt y then Node y insert x left right else Node y left insert x right val insert a gt a btree gt a btree lt fun gt 1 5 Imperative features Though all examples so far were written in purely applicative style Caml is also equipped with full imperative features This includes the usual while and for loops as well as mutable data structures such as arrays Arrays are either given in extension between and brackets or allocated and initialized with the Array create function then filled up later by assignments For instance the function below sums two vectors represented as float arrays componentwise let add_vect vi v2 let len min Array length vi Array length v2 in let res Array create len 0 0 in for i 0 to len 1 do res i lt vi i v2 i done res val add_vect float array gt float array gt float array lt fun gt add_vect 1 0 2 0
90. keys of all bindings in m and d1 dN are the associated data The order in which the bindings are presented to f is unspecified end module Make Ord OrderedType S with type key Ord t Functor building an implementation of the map structure given a totally ordered type Chapter 19 The standard library 275 19 18 Module Marshal marshaling of data structures This module provides functions to encode arbitrary data structures as sequences of bytes which can then be written on a file or sent over a pipe or network connection The bytes can then be read back later possibly in another process and decoded back into a data structure The format for the byte sequences is compatible across all machines for a given version of Objective Caml Warning marshaling is currently not type safe The type of marshaled data is not transmitted along the value of the data making it impossible to check that the data read back possesses the type expected by the context In particular the result type of the Marshal from_ functions is given as a but this is misleading the returned Caml value does not possess type a for all a it has one unique type which cannot be determined at compile type The programmer should explicitly give the expected type of the returned value using the following syntax Marshal from_channel chan type Anything can happen at run time if the object in the file does not belong to the given type The representat
91. library 363 external blit src a b c t gt dst a b c t gt unit Copy all elements of a big array in another big array Genarray blit src dst copies all elements of src into dst Both arrays src and dst must have the same number of dimensions and equal dimensions Copying a sub array of src to a sub array of dst can be achieved by applying Genarray blit to sub array or slices of src and dst external fill a b c t gt a gt unit Set all elements of a big array to a given value Genarray fill a v stores the value v in all elements of the big array a Setting only some elements of a to v can be achieved by applying Genarray fill to a sub array or a slice of a external map_file end Unix file_descr gt kind a b kind gt layout c layout gt shared bool gt dims int array gt a b c t Memory mapping of a file as a big array Genarray map_file fd kind layout shared dims returns a big array of kind kind layout layout and dimensions as specified in dims The data contained in this big array are the contents of the file referred to by the file descriptor fd as opened previously with Unix openfile for example If shared is true all modifications performed on the array are reflected in the file This requires that fd be opened with write permissions If shared is false modifications performed on the array are done in memory only using copy on write of the modified pa
92. line option cd directory Set the working directory for camldebug to directory pwd Print the working directory for camldebug 15 8 5 Turning reverse execution on and off In some cases you may want to turn reverse execution off This speeds up the program execution and is also sometimes useful for interactive programs Normally the debugger takes checkpoints of the program state from time to time That is it makes a copy of the current state of the program using the Unix system call fork If the variable checkpoints is set to off the debugger will not take any checkpoints set checkpoints on off Select whether the debugger makes checkpoints or not 184 15 8 6 Communication between the debugger and the program The debugger communicate with the program being debugged through a Unix socket You may need to change the socket name for example if you need to run the debugger on a machine and your program on another set socket socket Use socket for communication with the program socket can be either a file name or an Internet port specification host port where host is a host name or an Internet address in dot notation and port is a port number on the host On the debugged program side the socket name is passed either by the D command line option to camlrun or through the CAML_DEBUG_SOCKET environment variable 15 8 7 Fine tuning the debugger Several variables enables to fine tune the debugger Reasonable defaults are
93. method withdraw Euro c gt Euro c end One may wish to open an account and simultaneously deposit some initial amount Although the initial implementation did not address this requirement it can be achieved by using an initializer class account_with_deposit x object inherit account_with_history initializer balance lt x end class account_with_deposit Euro c gt object val mutable balance Euro c val mutable history Euro c operation list 70 method balance Euro c method deposit Euro c gt unit method history Euro c operation list method private trace Euro c operation gt unit method withdraw Euro c gt Euro c end A better alternative is class account_with_deposit x object self inherit account_with_history initializer self deposit x end class account_with_deposit Euro c gt object val mutable balance Euro c val mutable history Euro c operation list method balance Euro c method deposit Euro c gt unit method history Euro c operation list method private trace Euro c operation gt unit method withdraw Euro c gt Euro c end Indeed the latter is safer since the call to deposit will automatically benefit from safety checks and from the trace Let s test it let ccp new account_with_deposit euro 100 in let balance ccp withdraw euro 50 in ccp history Euro c operation list Deposit lt obj gt Retriev
94. more information see the description of module Lazy in the standard library section 19 14 7 5 Record copy with update The expression expr with Jbl expr Ibl expr builds a fresh record with fields Ibl 1bl equal to expr expr and all other fields having the same value as in the record expr In other terms it returns a shallow copy of the record expr except for the fields Ib Iblp which are initialized to expr expr For example type point x float y float z float let proj p p with x 0 0 x 0 0 y p y z p z let proj p The two definitions of proj above are equivalent 7 6 Local modules The expression let module module name module expr in expr locally binds the module expres sion module expr to the identifier module name during the evaluation of the expression expr It then returns the value of expr For example let remove_duplicates comparison_fun string_list let module StringSet Set Make struct type t string let compare comparison_fun end in StringSet elements List fold_right StringSet add string_list StringSet empty 128 Part III The Objective Caml tools 129 Chapter 8 Batch compilation ocamlc This chapter describes the Objective Caml batch compiler ocamlc which compiles Caml source files to bytecode object files and link these object files to produce standalone bytecode executable files These executable files are then run by the by
95. mutable or cyclic keys module type S sig type key type at val create int gt at val clear a t gt unit val add a t gt key key gt data a gt unit val remove a t gt key gt unit val find a t gt key gt a val find_all a t gt key gt a list val mem a t gt key gt bool val iter f key key gt data a gt unit gt a t gt unit end module Make H HashedType S with type key H t The functor Hashtbl Make returns a structure containing a type key of keys and a type a t of hash tables associating data of type a to keys of type key The operations perform similarly to those of the generic interface but use the hashing and equality functions specified in the functor argument H instead of generic equality and hashing The polymorphic hash primitive val hash a gt int Hashtbl hash x associates a positive integer to any value of any type It is guaranteed that ifx y then hash x hash y Moreover hash always terminates even on cyclic structures 262 val 19 12 Module Int32 32 bit integers val val val val val val val val val hash_param Hashtbl hash_param n m x computes a hash value for x with the same properties as for hash The two extra parameters n and m give more precise control over hashing Hashing performs a depth first right to left traversal of the structure x stopping after n meaningful
96. of flags and field width specifiers If too few arguments are provided printing stops just before converting the first missing argument val printf a out_channel unit format gt a Same as fprintf but output on stdout val eprintf a out_channel unit format gt a Same as fprintf but output on stderr val sprintf a unit string format gt a Same as fprintf but instead of printing on an output channel return a string containing the result of formatting the arguments val bprintf Buffer t gt a Buffer t unit format gt a Same as fprintf but instead of printing on an output channel append the formatted arguments to the given extensible buffer see module Buffer 282 19 24 Module Queue first in first out queues This module implements queues FIFOs with in place modification type at The type of queues containing elements of type a exception Empty val val val val val val val Raised when take is applied to an empty queue create unit gt at Return a new queue initially empty add a gt a t gt unit add x q adds the element x at the end of the queue q take at gt a take q removes and returns the first element in queue q or raises Empty if the queue is empty peek a t gt a peek q returns the first element in queue q without removing it from the queue or raises Empty if the queue is empty
97. of the buffer b add_substring t gt string gt pos int gt len int gt unit add_substring b s ofs len takes len characters from offset ofs in string s and appends them at the end of the buffer b 244 val add_buffer t gt src t gt unit add_buffer b1 b2 appends the current contents of buffer b2 at the end of buffer b1 b2 is not modified val add_channel t gt in_channel gt len int gt unit add_channel b ic n reads exactly n character from the input channel ic and stores them at the end of buffer b Raise End_of_file if the channel contains fewer than n characters val output_buffer out_channel gt t gt unit output_buffer oc b writes the current contents of buffer b on the output channel oc 19 4 Module Callback registering Caml values with the C runtime This module allows Caml values to be registered with the C runtime under a symbolic name so that C code can later call back registered Caml functions or raise registered Caml exceptions val register string gt a gt unit Callback register n v registers the value v under the name n C code can later retrieve a handle to v by calling caml_named_value n val register_exception string gt exn gt unit Callback register_exception n exn registers the exception contained in the exception value exn under the name n C code can later retrieve a handle to the exception by calling caml_named_value n The exception value thus obtained
98. page for a complete description type terminal_io Input modes mutable c_ignbrk bool Ignore the break condition mutable c_brkint bool Signal interrupt on break condition mutable c_ignpar bool Ignore characters with parity errors mutable c_parmrk bool Mark parity errors mutable c_inpck bool Enable parity check on input mutable c_istrip bool Strip 8th bit on input characters mutable c_inlcr bool Map NL to CR on input mutable c_igncr bool Ignore CR on input mutable c_icrnl bool Map CR to NL on input mutable c_ixon bool Recognize XON XOFF characters on input mutable c_ixoff bool Emit XON XOFF chars to control input flow Output modes mutable c_opost bool Enable output processing Control modes Chapter 20 The unix library Unix system calls 315 mutable mutable mutable mutable mutable mutable mutable mutable mutable c_obaud int c_ibaud int c_csize int c_cstopb int c_cread bool c_parenb bool c_parodd bool c_hupcl bool c_clocal bool Local modes mutable mutable mutable mutable mutable mutable mutable c_isig bool c_icanon bool c_noflsh bool c_echo bool c_echoe bool c_echok bool c_echonl bool Control characters mutable mutable mutable mutable mutable mutable mutable mutable mutable mutable
99. parameters If any method in the class type body is virtual the definition must be flagged virtual Two class type definitions match if they have the same type parameters and the types they expand to match 6 10 Module types module specifications Module types are the module level equivalent of type expressions they specify the general shape and type properties of modules 118 module type modtype path sig specification end functor module name module type gt module type module type with mod constraint and mod constraint module type specification val value name typexpr external value name typexpr external declaration type definition exception definition class specification classtype definition module module name module type module module name module name module type module type module type modtype name module type modtype name module type open module path include modtype path mod constraint type type parameters typeconstr typexpr module module path extended module path 6 10 1 Simple module types The expression modtype path is equivalent to the module type bound to the name modtype path The expression module type denotes the same type as module type 6 10 2 Signatures Signatures are type specifications for structures Signatures sig end are collections of type specifications for value names type names exceptions module names and module ty
100. pattern and whose tails match patterns This pattern behaves like pattern patterns The pattern pattern pattern matches lists of length n whose elements match pattern pattern respectively This pattern behaves like pattern pattern 1 Polymorphic variant patterns The pattern tag name pattern matches all polymorphic variants whose tag is equal to tag name and whose argument matches pattern Variant abbreviation patterns If the type a b typeconstr tag t tag tn is defined then the pattern typeconstr is a shorthand for the or pattern tag _ t1 tag _ tn It matches all values of type typeconstr 98 Tuple patterns The pattern pattern pattern matches n tuples whose components match the patterns pattern through pattern That is the pattern matches the tuple values v1 Vn such that pattern matches v fori 1 n Record patterns The pattern field pattern field pattern matches records that define at least the fields field through field and such that the value associated to field match the pattern pattern for i 1 n The record value can define more fields than field field the values associated to these extra fields are not taken into account for matching Chapter 6 The Objective Caml language 99 6 7 Expressions expr value path constant expr begin expr en
101. present in memory At start up the toplevel system contains implementations for all the modules in the the standard library Implementations for user modules can be entered with the load directive described above Referencing a unit for which no implementation has been provided results in the error Reference to undefined global Note that entering open mod merely accesses the compiled interface cmi file for mod but does not load the implementation of mod and does not cause any error if no implementation of mod has been loaded The error reference to undefined global mod will occur only when executing a value or module definition that refers to mod 9 4 Common errors This section describes and explains the most frequently encountered error messages Cannot find file filename The named file could not be found in the current directory nor in the directories of the search path If filename has the format mod cmi this means you have referenced the compilation unit mod but its compiled interface could not be found Fix compile mod mli or mod m1 first to create the compiled interface mod cmi If filename has the format mod cmo this means you are trying to load with load a bytecode object file that does not exist yet Fix compile mod m1 first If your program spans several directories this error can also appear because you haven t specified the directories to look into Fix use the directory directive to add the
102. printer output It is called with a string s a start position p and a number of characters n it is supposed to output characters p to ptn 1 of s The flush function is called whenever the pretty printer is flushed using print_flush or print_newline val get_formatter_output_functions unit gt buf string gt pos int gt len int gt unit unit gt unit Return the current output functions of the pretty printer Changing the meaning of indentation and line breaking val set_all_formatter_output_functions out buf string gt pos int gt len int gt unit gt flush unit gt unit gt newline unit gt unit gt space int gt unit gt unit set_all_formatter_output_functions out flush outnewline outspace redirects the pretty printer output to the functions out and flush as described in set_formatter_output_functions In addition the pretty printer function that outputs a newline is set to the function outnewline and the function that outputs indentation spaces is set to the function outspace This way you can change the meaning of indentation which can be something else than just printing a space character and the meaning of new lines opening which can be connected to any other action needed by the application at hand The two functions outspace and outnewline are normally connected to out and flush respective default values for outspace and outnewline are out String make n
103. regexp definition Concerning the precedences of operators x and have highest precedence followed by then concatenation then alternation 12 2 5 Actions The actions are arbitrary Caml expressions They are evaluated in a context where the identifier lexbuf is bound to the current lexer buffer Some typical uses for lexbuf in conjunction with the operations on lexer buffers provided by the Lexing standard library module are listed below Lexing lexeme lexbuf Return the matched string Lexing lexeme_char lexbuf n Return the nt character in the matched string The first character corresponds to n 0 160 Lexing lexeme_start lexbuf Return the absolute position in the input text of the beginning of the matched string The first character read from the input text has position 0 Lexing lexeme_end lexbuf Return the absolute position in the input text of the end of the matched string The first character read from the input text has position 0 entrypoint lexbuf Where entrypoint is the name of another entry point in the same lexer definition Recursively call the lexer on the given entry point Useful for lexing nested comments for example 12 2 6 Reserved identifiers All identifiers starting with __ocaml_lex are reserved for use by ocamllex do not use any such identifier in your programs 12 3 Overview of ocamlyacc The ocamlyacc command produces a parser from a context free grammar specification with at tached
104. registered with the garbage collector using the register_global_root function Registration of a global variable v is achieved by calling register_global_root amp v just before a valid value is stored in v for the first time A registered global variable v can be un registered by calling remove_global_root amp v Note The CAML macros use identifiers local variables type identifiers structure tags that start with cam1__ Do not use any identifier starting with caml__ in your programs 17 5 2 Low level interface We now give the GC rules corresponding to the low level allocation functions alloc_small and alloc_shr You can ignore those rules if you stick to the simplified allocation function alloc Rule 5 After a structured block a block with tag less than No_scan_tag is allocated with the low level functions all fields of this block must be filled with well formed values before the next allocation operation If the block has been allocated with alloc_small filling is performed by direct assignment to the fields of the block Field v n un If the block has been allocated with alloc_shr filling is performed through the initialize function initialize amp Field v n wp The next allocation can trigger a garbage collection The garbage collector assumes that all structured blocks contain well formed values Newly created blocks contain random data which generally do not represent well formed values If you really need t
105. repr k x gt end class safe_money float gt object a val repr float method print unit method times float gt a end Here the representation of the object is known only to a particular object To make it available to other objects of the same class we are forced to make it available to the whole world However we can easily restrict the visibility of the representation using the module system module type MONEY sig type t class c float gt object a val repr t method value t method print unit method times float gt a method leq a gt bool method plus a gt a end end module Euro MONEY struct type t float class c x object self a val repr x HHH HH HF HHH HHH HOH H FH OF method value repr method print print_float repr method times k lt repr k x gt method leq p a repr lt p value method plus p a lt repr x p value gt end end HH HH H HH OF Another example of friend functions may be found in section 5 2 3 These examples occur when a group of objects here objects of the same class and functions should see each others internal representation while their representation should be hidden from the outside The solution is always to define all friends in the same module give access to the representation and use a signature constraint to make the representation abstract outside of the
106. representation and then a constraint clause The identifier is the name of the type constructor being defined The optional type parameters are either one type variable ident for type constructors with one parameter or a list of type variables ident ident for type constructors with several parameters These type parameters can appear in the type expressions of the right hand side of the definition The optional type equation typexpr makes the defined type equivalent to the type expression typexpr on the right of the sign one can be substituted for the other during typing If no type equation is given a new type is generated the defined type is incompatible with any other type The optional type representation describes the data structure representing the defined type by giving the list of associated constructors if it is a variant type or associated fields if it is a record type If no type representation is given nothing is assumed on the structure of the type besides what is stated in the optional type equation The type representation constr decl constr decl describes a variant type The constructor declarations constr decl constr decl describe the constructors associated to this variant type The constructor declaration ncconstr name of typexpr declares the name ncconstr name as a non constant constructor whose argument has type typexpr The constructor declaration cconstr name declares the name c
107. respective interfaces Chapter 7 Language extensions This chapter describes the language features that are implemented in Objective Caml but not described in the Objective Caml reference manual In contrast with the fairly stable kernel language that is described in the reference manual the extensions presented here are still experimental and may be removed or changed in the future 7 1 Streams and stream parsers Objective Caml comprises a library type for streams possibly infinite sequences of elements that are evaluated on demand and associated stream expressions to build streams and stream patterns to destructure streams Streams and stream patterns provide a natural approach to the writing of recursive descent parsers Streams are presented by the following extensions to the syntactic classes of expressions expr stream component stream matching stream pattern stream pat comp lt gt lt stream component stream component gt parser pattern stream matching match expr with parser pattern stream matching gt expr expr stream pattern pattern gt expr stream pattern pattern gt expr lt gt lt stream pat comp stream pat comp expr gt pattern when expr pattern expr ident 125 126 Stream expressions are bracketed by lt and gt They represent the concatenation of their components The component expr represents the one element stream
108. set_binary_mode_out oc false sets the channel oc to text mode depending on the operating system some translations may take place during output For instance under Windows end of lines will be translated from n to r n This function has no effect under operating systems that do not distinguish between text mode and binary mode 234 General input functions val val val val val val val open_in string gt in_channel Open the named file for reading and return a new input channel on that file positionned at the beginning of the file Raise Sys_error if the file could not be opened open_in_bin string gt in_channel Same as open_in but the file is opened in binary mode so that no translation takes place during reads On operating systems that do not distinguish between text mode and binary mode this function behaves like open_in open_in_gen mode open_flag list gt perm int gt string gt in_channel Open the named file for reading as above The extra arguments mode and perm specify the opening mode and file permissions open_in and open_in_bin are special cases of this function input_char in_channel gt char Read one character from the given input channel Raise End_of_file if there are no more characters to read input_line in_channel gt string Read characters from the given input channel until a newline character is encountered Return the string of all characters read witho
109. the program being debugged The code for the printing functions must therefore be loaded explicitly in the debugger load_printer file name Load in the debugger the indicated cmo or cma object file The file is loaded in an envi ronment consisting only of the Objective Caml standard library plus the definitions provided by object files previously loaded using load_printer If this file depends on other object files not yet loaded the debugger automatically loads them if it is able to find them in the search path The loaded file does not have direct access to the modules of the program being debugged install_printer printer name Register the function named printer name a value path as a printer for objects whose types match the argument type of the function That is the debugger will call printer name when it has such an object to print The printing function printer name must use the Format library module to produce its output otherwise its output will not be correctly located in the values printed by the toplevel loop The value path printer name must refer to one of the functions defined by the object files loaded using load_printer It cannot reference the functions of the program being debugged remove_printer printer name Remove the named function from the table of value printers 15 9 Miscellaneous commands list module beginning end List the source of module module from line number beginning to line number end By de
110. the functions raise_constant raise_with_arg and raise_with_string described in section 17 4 5 to actually raise the exception For example here is a C function that raises the Error exception with the given argument void raise_error char msg raise_with_string caml_named_value test exception msg 17 7 4 Main program in C In normal operation a mixed Caml C program starts by executing the Caml initialization code which then may proceed to call C functions We say that the main program is the Caml code In some applications it is desirable that the C code plays the role of the main program calling Caml functions when needed This can be achieved as follows e The C part of the program must provide a main function which will override the default main function provided by the Caml runtime system Execution will start in the user defined main function just like for a regular C program e At some point the C code must call caml_main argv to initialize the Caml code The argv argument is a C array of strings type char which represents the command line arguments as passed as second argument to main The Caml array Sys argv will be initialized from this parameter For the bytecode compiler argv 0 and argv 1 are also consulted to find the file containing the bytecode e The call to caml_main initializes the Caml runtime system loads the bytecode in the case of the bytecode compiler and executes the initialization
111. the list of all elements of the given set The returned list is sorted in increasing order with respect to the ordering Ord compare where Ord is the argument given to Set Make val min_elt t gt elt Return the smallest element of the given set with respect to the Ord compare ordering or raise Not_found if the set is empty val max_elt t gt elt Same as min_elt but returns the largest element of the given set val choose t gt elt Return one element of the given set or raise Not_found if the set is empty Which element is chosen is unspecified but equal elements will be chosen for equal sets end module Make Ord OrderedType S with type elt Ord t Functor building an implementation of the set structure given a totally ordered type 286 19 27 Module Sort sorting and merging lists This module is obsolete and exists only for backward compatibility The sorting functions in Array and List should be used instead The new functions are faster and use less memory val list order a gt a gt bool gt a list gt a list Sort a list in increasing order according to an ordering predicate The predicate should return true if its first argument is less than or equal to its second argument val array order a gt a gt bool gt a array gt unit Sort an array in increasing order according to an ordering predicate The predicate should return true if its first argument is less t
112. the program performs a function application it saves the location of the application the return address in a block of data called a stack frame The frame also contains the local variables Chapter 15 The debugger ocamldebug 181 of the caller function All the frames are allocated in a region of memory called the call stack The command backtrace or bt displays parts of the call stack At any time one of the stack frames is selected by the debugger several debugger commands refer implicitly to the selected frame In particular whenever you ask the debugger for the value of a local variable the value is found in the selected frame The commands frame up and down select whichever frame you are interested in When the program stops the debugger automatically selects the currently executing frame and describes it briefly as the frame command does frame Describe the currently selected stack frame frame frame number Select a stack frame by number and describe it The frame currently executing when the program stopped has number 0 its caller has number 1 and so on up the call stack backtrace count bt count Print the call stack This is useful to see which sequence of function calls led to the currently executing frame With a positive argument print only the innermost count frames With a negative argument print only the outermost count frames up count Select and display the stack frame just above the selec
113. the user provided serialize function That function is responsible for writing the data contained in the custom block using the serialize_ functions defined in lt caml intext h gt and listed below The user provided serialize function must then store in its wsize_32 and wsize_64 parameters the sizes in bytes of the data part of the custom block on a 32 bit architecture and on a 64 bit architecture respectively The serialize field can be set to custom_serialize_default in which case the Failure exception is raised when attempting to serialize the custom block e unsigned long deserialize void dst The deserialize field contains a pointer to a C function that is called whenever a custom block with identifier identifier needs to be deserialized un marshaled using the Caml functions input_value or Marshal from_ This user provided function is responsible for reading back the data using the deserialize_ functions defined in lt caml intext h gt and listed below It must store the data at the pointer given as the dst argument then return the size in bytes of the data The deserialize field can be set to custom_deserialize_default to indicate that deseri alization is not supported In this case do not register the struct custom_operations with the deserializer using register_custom_operations see below 17 9 2 Allocating custom blocks Custom blocks must be allocated via the alloc_custom function alloc_custom ops size u
114. this expression is used in the rest of the program If the two types t and t2 are not compatible then the error above is produced In some cases it is hard to understand why the two types t and t2 are incompatible For instance the compiler can report that expression of type foo cannot be used with type foo and it really seems that the two types foo are compatible This is not always true Two type constructors can have the same name but actually represent different types This can happen if a type constructor is redefined Example type foo A B let f function A gt 0 B gt 1 type foo C D f C Chapter 8 Batch compilation ocamlc 137 This result in the error message expression C of type foo cannot be used with type foo The type of this expression t contains type variables that cannot be generalized Type variables a b in a type t can be in either of two states generalized which means that the type tis valid for all possible instantiations of the variables and not gener alized which means that the type tis valid only for one instantiation of the variables In a let binding let name expr the type checker normally generalizes as many type variables as possible in the type of expr However this leads to unsoundness a well typed program can crash in conjunction with polymorphic mutable data structures To avoid this general ization is performed at let bindings only if the bound expressio
115. to recover the actual Caml value If no value is registered under the name n the null pointer is returned For example here is a C wrapper that calls the Caml function f above void call_caml_f int arg callback caml_named_value test function Val_int arg The pointer returned by caml_named_value is constant and can safely be cached in a C variable to avoid repeated name lookups On the other hand the value pointed to can change during garbage collection and must always be recomputed at the point of use Here is a more efficient variant of call_caml_f above that calls caml_named_value only once void call_caml_f int arg static value closure_f NULL if closure_f NULL First time around look up by name closure_f caml_named_value test function callback closure_f Val_int arg 17 7 3 Registering Caml exceptions for use in C functions The registration mechanism described above can also be used to communicate excep tion identifiers from Caml to C The Caml code registers the exception by evaluating Callback register_exception n ezn where n is an arbitrary name and ezn is an exception value of the exception to register For example Chapter 17 Interfacing C with Objective Caml 211 exception Error of string let _ Callback register_exception test exception Error any string The C code can then recover the exception identifier using caml_named_value and pass it as first argument to
116. treat primitive types such as integers and strings as objects Although this is usually uninteresting for integers or strings there may be some situations where this is desirable The class money above is such an example We show here how to do it for strings 5 2 1 Strings A naive definition of strings as objects could be class ostring s object method get n String get n method set n c String set nc method print print_string s method copy new ostring String copy s end class ostring string gt 74 object method copy ostring method get string gt int gt char method print unit method set string gt int gt char gt unit end However the method copy returns an object of the class string and not an objet of the current class Hence if the class is further extended the method copy will only return an object of the parent class class sub_string s object inherit ostring s method sub start len new sub_string String sub s start len end class sub_string string gt object method copy ostring method get string gt int gt char method print unit method set string gt int gt char gt unit method sub int gt int gt sub_string end As seen in section 3 14 the solution is to use functional update instead We need to create an instance variable containing the representation s of the string class better_string s objec
117. typeconstr path tag list typexpr typeconstr path tag list typexpr typexpr typeconstr path tag list method name typexpr gt tag name The table below shows the relative precedences and associativity of operators and non closed type constructions The constructions with higher precedences come first Operator Associativity gt as Type constructor application right Type expressions denote types in definitions of data types as well as in type constraints over patterns and expressions Type variables The type expression ident stands for the type variable named ident The type expression _ stands for an anonymous type variable In data type definitions type variables are names for the data type parameters In type constraints they represent unspecified types that can be instantiated by any type to satisfy the type constraint 94 Parenthesized types The type expression typexpr denotes the same type as typexpr Function types The type expression typexpr gt typexpr denotes the type of functions mapping arguments of type typexpr to results of type typexprs label typexpr gt typexpry denotes the same function type but the argument is labeled label label typexpr gt typexpr denotes the type of functions mapping an optional labeled argu ment of type typexpr to results of type typexprg That is the physical type of the function will be typ
118. usual search_forward pat regexp gt string gt pos int gt int search_forward r s start searchs the string s for a substring matching the regular expression r The search starts at position start and proceeds towards the end of the string Return the position of the first character of the matched substring or raise Not_found if no substring matches search_backward pat regexp gt string gt pos int gt int Same as search_forward but the search proceeds towards the beginning of the string string_partial_match pat regexp gt string gt pos int gt bool Similar to string_match but succeeds whenever the argument string is a prefix of a string that matches This includes the case of a true complete match Chapter 22 The str library regular expressions and string processing 327 val matched_string string gt string matched_string s returns the substring of s that was matched by the latest string_match search_forward or search_backward The user must make sure that the parameter s is the same string that was passed to the matching or searching function val match_beginning unit gt int val match_end unit gt int match_beginning returns the position of the first character of the substring that was matched by string_match search_forward or search_backward match_end returns the position of the character following the last character of the matched substring val matched_group int gt string gt str
119. val val val val Raised by the following functions when an error is encountered opendbm string gt mode open_flag list gt perm int gt t Open a descriptor on an NDBM database The first argument is the name of the database without the dir and pag suffixes The second argument is a list of flags Dbm_rdonly opens the database for reading only Dbm_wronly for writing only Dobm_rdwr for reading and writing Dbm_create causes the database to be created if it does not already exist The third argument is the permissions to give to the database files if the database is created close t gt unit Close the given descriptor find t gt string gt string find db key returns the data associated with the given key in the database opened for the descriptor db Raise Not_found if the key has no associated data add t gt key string gt data string gt unit add db key data inserts the pair key data in the database db If the database already contains data associated with key raise Dbm_error Entry already exists replace t gt key string gt data string gt unit replace db key data inserts the pair key data in the database db If the database already contains data associated with key that data is discarded and silently replaced by the new data remove t gt string gt unit remove db key data removes the data associated with key in db If key has no associated data raise Dbm_error db
120. val remove_assoc a gt a b list gt a b list remove_assoc a 1 returns the list of pairs 1 without the first pair with key a if any Not tail recursive val remove_assq a gt a b list gt a b list Same as remove_assq but uses physical equality instead of structural equality to compare keys Not tail recursive Chapter 19 The standard library 273 Lists of pairs val split a b list gt a list b list Transform a list of pairs into a pair of lists split a1 b1 an bn is fal an b1 bn Not tail recursive val combine a list gt b list gt a b list Transform a pair of lists into a list of pairs combine a1 an b1 bn is al b1 an bn Raise Invalid_argument if the two lists have different lengths Not tail recursive Sorting val sort cmp a gt a gt int gt a list gt a list Sort a list in increasing order according to a comparison function The comparison function must return 0 if it arguments compare as equal a positive integer if the first is greater and a negative integer if the first is smaller For example the compare function is a suitable comparison function The resulting list is sorted in increasing order List sort is guaranteed to run in constant heap space in addition to the size of the result list and logarithmic stack space The current impl
121. values Hence they can be assigned to resulting in an in place modification of value v Assigning directly to Field v n must be done with care to avoid confusing the garbage collector see below 17 4 4 Allocating blocks Simple interface Atom t returns an atom zero sized block with tag t Zero sized blocks are preallocated outside of the heap It is incorrect to try and allocate a zero sized block using the functions below For instance Atom 0 represents the empty array alloc n t returns a fresh block of size n with tag t If tis less than No_scan_tag then the fields of the block are initialized with a valid value in order to satisfy the GC constraints alloc_tuple n returns a fresh block of size n words with tag 0 alloc_string n returns a string value of length n characters The string initially contains garbage copy_string s returns a string value containing a copy of the null terminated C string s a char copy_double d returns a floating point value initialized with the double d copy_int32 7 copy_int64 7 and copy_nativeint i return a value of Caml type int32 int64 and nativeint respectively initialized with the integer i alloc_array f a allocates an array of values calling function f over each element of the input array a to transform it into a value The array a is an array of pointers terminated by the null pointer The function f receives each pointer as argument and returns a value
122. whose element is the value of expr The component expr represents a sub stream For instance if both s and t are streams of integers then lt 1 s t 2 gt is a stream of integers containing the element 1 then the elements of s then those of t and finally 2 The empty stream is denoted by lt gt Unlike any other kind of expressions in the language stream expressions are submitted to lazy evaluation the components are not evaluated when the stream is built but only when they are accessed during stream matching The components are evaluated once the first time they are accessed the following accesses reuse the value computed the first time Stream patterns also bracketed by lt and gt describe initial segments of streams In particular the stream pattern lt gt matches all streams Stream pattern components are matched against the corresponding elements of a stream The component pattern matches the corresponding stream element against the pattern if followed by when the match is accepted only if the result of the guard expression is true The component pattern expr applies the function denoted by expr to the current stream then matches the result of the function against pattern Finally the component ident simply binds the identifier to the stream being matched Stream matching proceeds destructively once a component has been matched it is discarded from the stream by in place modification Stream matchi
123. x_init new point x_init 10 10 val new_adjusted_point int gt point lt fun gt However the former pattern is generally more appropriate since the code for adjustment is part of the definition of the class and will be inherited This ability provides class constructors as can be found in other languages Several constructors can be defined this way to build objects of the same class but with different initialization patterns an alternative is to use initializers as decribed below in section 3 3 3 2 Reference to self A method can also send messages to self that is the current object For that self must be explicitly bound here to the variable s s could be any identifier even though we will often choose the name self class printable_point x_init object s val mutable x x_init method move d x lt x d method print print_int s get_x end class printable_point int gt object val mutable x int method get_x int method move int gt unit method print unit end method get_x x let p new printable_point 7 val p printable_point lt obj gt p print 7 unit Dynamically the variable s is bound at the invocation of a method In particular when the class printable_point will be inherited the variable s will be correctly bound to the object of the subclass 3 3 Initializers Let bindings within class definitions are evaluated before the
124. 0 020000 02 eee eee 369 V Appendix 373 Index to the library assomit p Seta WO See BS de He Bo Go a e Ee Se oe EE eS 375 IndeX of keywords re 4 cea 9 252 iG et a hae at Oy He Oe BRS Bee Hee 385 Foreword This manual documents the release 3 00 of the Objective Caml system It is organized as follows e Part I An introduction to Objective Caml gives an overview of the language e Part II The Objective Caml language is the reference description of the language e Part III The Objective Caml tools documents the compilers toplevel system and pro gramming utilities e Part IV The Objective Caml library describes the modules provided in the standard library e Part V Appendix contains an index of all identifiers defined in the standard library and an index of keywords Conventions Objective Caml runs on several operating systems The parts of this manual that are specific to one operating system are presented as shown below MacOS This is material specific to MacOS 7 8 9 MacOS X is a version of Unix as far as Objective Caml is concerned Unix This is material specific to Unix Windows This is material specific to MS Windows NT and 95 License The Objective Caml system is copyright 1996 1997 1998 Institut National de Recherche en Informatique et en Automatique INRIA INRIA holds all ownership rights to the Objective Caml system See the file LICENSE in the distribu
125. 1 lt 2 false bool false as char a Hello world string Hello world Predefined data structures include tuples arrays and lists General mechanisms for defining your own data structures are also provided They will be covered in more details later for now we concentrate on lists Lists are either given in extension as a bracketed list of semicolon separated elements or built from the empty list pronounce nil by adding elements in front using the cons operator let 1 is al tale told etc val 1 string list is a tale told etc Life Ty string list Life is a tale told etc As with all other Caml data structures lists do not need to be explicitly allocated and deallocated from memory all memory management is entirely automatic in Caml Similarly there is no explicit handling of pointers the Caml compiler silently introduces pointers where necessary As with most Caml data structures inspecting and destructuring lists is performed by pattern matching List patterns have the exact same shape as list expressions with identifier representing unspecified parts of the list As an example here is insertion sort on a list let rec sort lst match lst with 0 gt O head tail gt insert head sort tail and insert elt lst match lst with Chapter 1 The core language 13
126. 119 121 123 val 112 113 115 117 118 virtual 112 113 116 117 when 99 103 while 105 with see match try 117 121 127
127. 3 clear_graph 340 clear_nonblock 303 clear_parser 280 close 300 348 close_box 248 close_graph 340 close_in 235 close_out 233 close_process 305 close_process_full 305 close_process_in 305 close_process_out 305 close_tbox 250 closedir 304 closeTk 352 code 244 combine 273 command 291 compact 258 compare 224 compare_num 321 concat 241 245 270 289 Condition module 334 connect 311 338 contains 290 contains_from 290 contents 243 copy 241 279 289 cos 227 cosh 228 count 288 counters 257 create 240 243 260 282 286 289 293 332 334 335 create_image 344 create_matrix 241 create_process 304 create_process_env 304 current 240 current_dir_name 245 current_point 342 current_x 342 current_y 342 INDEX TO THE LIBRARY cyan 341 data_size 276 Dbm module 347 Dbm_error exception 348 decr 236 decr_num 321 delay 332 descr_of_in_channel 300 descr_of_out_channel 300 destroy 352 Digest module 245 dirname 246 display_mode 346 div 262 265 277 div_num 320 Division_by_zero exception 223 draw_arc 342 draw_char 343 draw_circle 343 draw_ellipse 343 draw_image 344 draw_rect 342 draw_string 343 dump_image 344 dup 303 dup2 303 Dynlink module 349 empty 288 Empty exception 282 286 End_of_file exception 223 environment 298 eprintf 255 281 eq_num 321 err_formatter 252 Error exception 287 350 error_message 2
128. 4 max_array_length 291 max_int 226 263 265 278 max_num 321 max_string_length 291 mem 260 271 mem_assoc 272 mem_assq 272 memq 271 merge 286 min 224 min_int 226 263 265 278 min_num 321 minor 257 minus_num 320 minus_one 262 264 277 mkdir 303 mkfifo 304 mktime 307 mod operator 226 mod_float 228 mod_num 320 modf 228 mouse_pos 345 moveto 342 mul 262 265 277 mult_num 320 Mutex module 334 nat_of_num 322 nativeint 359 Nativeint module 277 neg 262 265 277 new_channel 335 next 288 nextkey 348 nice 299 not 225 Not_found exception 223 npeek 288 nth 269 Num module 319 num_of_big_int 322 num_of_int 322 num_of_nat 322 num_of_ratio 322 num_of_string 322 of_channel 287 of _float 264 266 278 of _int 263 266 278 of _int32 266 279 of _list 242 287 of _nativeint 267 of_string 264 267 279 287 one 262 264 277 Oo module 279 open_box 247 open_connection 313 338 open_graph 340 open_hbox 250 open_hovbox 250 open_hvbox 250 open_in 234 open_in_bin 234 open_in_gen 234 open_out 232 open_out_bin 232 open_out_gen 232 open_process 305 337 open_process_full 305 337 open_process_in 305 337 open_process_out 305 337 open_tbox 250 open_vbox 250 opendbm 348 opendir 304 openfile 300 openTk 352 or operator 225 OrderedType module type 273 283 os_type 291 INDEX TO THE LIBRARY out_c
129. 6 Heap compaction 32 Change of GC parameters 64 Computation of major GC slice size l stack_limit The limit in words of the stack size h The initial size of the major heap in words The multiplier is k M or G for multiplication by 2 22 and 2 respectively For example on a 32 bit machine under bash the command export OCAMLRUNPARAM s 256k v 1 tells a subsequent ocamlrun to set its initial minor heap size to 1 megabyte and to print a message at the start of each major GC cycle PATH List of directories searched to find the bytecode executable file 10 3 Common errors This section describes and explains the most frequently encountered error messages filename no such file or directory If filename is the name of a self executable bytecode file this means that either that file does not exist or that it failed to run the ocamlrun bytecode interpreter on itself The second possibility indicates that Objective Caml has not been properly installed on your system Chapter 10 The runtime system ocamlrun 149 Cannot exec camlrun When launching a self executable bytecode file The ocamlrun could not be found in the executable path Check that Objective Caml has been properly installed on your system Cannot find the bytecode file The file that ocamlrun is trying to execute e g the file given as first non option argument to ocamlrun either does not exist or is not a valid executable bytecode file Tr
130. 7 The parameter x_init is of course visible in the whole body of the definition including methods For instance the method get_offset in the class below returns the position of the object to the origin class point x_init object val mutable x x_init method get_x x method get_offset x x_init method move d x lt x d end class point int gt object val mutable x int method get_offset int method get_x int method move int gt unit end Expressions can be evaluated and bound before defining the object body of the class This is useful to enforce invariants For instance points can be automatically adjusted to grid as follows class adjusted_point x_init let origin x_init 10 10 in object val mutable x origin method get_x x method get_offset x origin method move d x lt x d end class adjusted_point int gt object val mutable x int method get_offset int method get_x int method move int gt unit end One could also raise an exception if the x_init coordinate is not on the grid In fact the same effect could here be obtained by calling the definition of class point with the value of the origin class adjusted_point x_init point x_init 10 10 class adjusted_point int gt point An alternative solution would have been to define the adjustment in a special allocation function 38 let new_adjusted_point
131. 97 350 escaped 244 289 establish_server 313 338 Event module 335 execv 298 337 execve 298 337 execvp 298 337 execvpe 298 exists 271 377 exists2 271 exit 236 332 Exit exception 223 exp 227 Failure exception 223 287 failwith 223 fchmod 302 fchown 302 file 245 file_exists 291 Filename module 245 fill 241 289 293 fill_arc 343 fill_circle 344 fill_ellipse 344 fill_poly 343 fill_rect 343 filter 272 finalise 258 find 260 272 348 find_all 260 272 first_chars 329 firstkey 348 flatten 270 float 228 283 float32 359 float64 359 float_of_int 228 float_of_num 322 float_of_string 229 floor 228 floor_nun 320 flush 232 flush_str_formatter 253 fold_left 242 270 fold_left2 271 fold_right 242 270 fold_right2 271 for_all 271 for_all12 271 force 127 267 force_newline 249 foreground 341 fork 299 378 format 264 267 279 Format module 247 formatter_of_buffer 252 formatter_of_out_channel 252 fortran_layout 360 fprintf 254 280 frexp 228 from 287 from_channel 268 276 from_function 268 from_string 268 276 fst 230 fstat 302 ftruncate 301 full_init 283 full_major 258 full_split 328 Gc module 255 ge_num 321 Genarray module 360 genarray_of_arrayl1 369 genarray_of_array2 369 genarray_of_array3 369 Genlex module 259 get 240 257 288 293 get_all_formatter_output_functions 252 get_appr
132. 992 ACM conference on Lisp and Functional Programming 7 2 Range patterns In patterns Objective Caml recognizes the form c gt d two character literals separated by as shorthand for the pattern 262 Peg Got la ey id where c1 C2 Cn are the characters that occur between c and din the ASCII character set For instance the pattern 0 9 matches all characters that are digits Chapter 7 Language extensions 127 7 3 Assertion checking Objective Caml supports the assert construct to check debugging assertions The expression assert expr evaluates the expression expr and returns if expr evaluates to true Otherwise the exception Assert_failure is raised with the source file name and the location of expr as arguments Assertion checking can be turned off with the noassert compiler option As a special case assert false is reduced to raise Assert_failure which is poly morphic and is not turned off by the noassert option 7 4 Deferred computations The expression lazy expr returns a value v of type Lazy t that encapsulates the computation of expr The argument expr is not evaluated at this point in the program Instead its evaluation will be performed the first time Lazy force is applied to the value v returning the actual value of expr Subsequent applications of Lazy force to v do not evaluate expr again The expression lazy expr is equivalent to ref Lazy Delayed fun gt expr For
133. A of string B gt bool lt fun gt let f x f1 x amp amp f2 x val f K A of string amp int B gt bool lt fun gt Here f1 and f2 both accept the variant tags A and B but the argument of A is int for f1 and string for 2 In f s type C only accepted by f1 disappears but both argument types appear for Aas int amp string This means that if we pass the variant tag A to f its argument should be both int and string Since there is no such value f cannot be applied to A and B is the only accepted input Even if a value has a fixed variant type one can still give it a larger type through coercions Coercions are normally written with both the source type and the destination type but in simple cases the source type may be omitted type a wlist Nil Cons of a a wlist Snoc of a wlist a type a wlist Nil Cons of a a wlist Snoc of a wlist a let wlist_of_vlist 1 1 a vlist gt a wlist val wlist_of_vlist a vlist gt a wlist lt fun gt fun x gt x gt AI BI C lt A B C gt A B C lt fun gt You may also selectively coerce values through pattern matching Chapter 2 Labels and variants 33 let split_cases function Nil Cons _ as x gt A x Snoc _ as x gt Bx 3 val split_cases lt
134. CE Toplevel directives o co eg see Sat Boe See Boe ate Doe Pa bee Ra es The toplevel and the module system 0 0000 epee ee COMMON ECITOLS ad wa Lek ahd eo As Pe anes Wie Eade e alk dangan Aah s Building custom toplevel systems ocamlmktop 2520485 OPTIONS i e nee wees SO he Ee hy Se aad es Bo et et Be 10 The runtime system ocamlrun 10 1 10 2 10 3 COVER VIC Ws cei Se coe inte bos Solids pn ote oo oe dote ee Ea et Debye Wt VE ce tah ath noth ee ht eked Options mhua wah le pated Goes PIPL et ee bose tl Ga a Bs COMMON CLrOLs tyes ea uae ee os ek eee A ete De Be eh eel ee bk Bas A es 11 Native code compilation ocamlopt 11 1 11 2 11 3 11 4 Overview of the compiler grr cen gg So el Po ee Oe Bae ee eS VO GIOMS a ae Secret Sepa eas eon See pa ae ase eras ante GEN Sor eae eens het COMMON ETOLS Shes iad doe be eae odia ew ee Swe nea Ae Compatibility with the bytecode compiler ooo a 12 Lexer and parser generators ocamllex ocamlyacc 12 1 12 2 12 3 12 4 12 5 12 6 12 7 Overview of ocaml lek giiecouig g amp ES BSS ce ao es ee Be RO SE PD Syntax of lexer definitions 0 20 0 2 e ee Overview Of ocamlyace is ong SA elle ge Oe a a E A a Syntax of grammar definitions 2 2 2 ee OPtONS 3 alae wh a BS oe A ee aoe Be a A aa oh te OOK oe BL A complete example ooo ee COMMON CTLOES yo ws Ble ne eg es a A Ae amp OR Ee a eee ead 13 Dependency generator o
135. Caml versions of the lexer generator Lex and the parser generator Yacc see chapter 12 which handle LALR 1 languages using push down automata on the other hand a predefined type of streams of characters or tokens and pattern matching over streams which facilitate the writing of recursive descent parsers for LL 1 languages An example using ocamllex and ocamlyacc is given in chapter 12 Here we will use stream parsers open Genlex let lexer make_lexer C Ws 4n wow Maps T val lexer char Stream t gt Genlex token Stream t lt fun gt For the lexical analysis phase transformation of the input text into a stream of tokens we use a generic lexer provided in the standard library module Genlex The make_lexer function takes a list of keywords and returns a lexing function that tokenizes an input stream of characters Tokens are either identifiers keywords or literals integer floats characters strings Whitespace and comments are skipped let token_stream lexer Stream of_string 1 0 x val token_stream Genlex token Stream t lt abstr gt Stream next token_stream Genlex token Float 1 000000 Stream next token_stream Genlex token Kwd Stream next token_stream Genlex token Ident x 22 The parser itself operates by pattern matching on the stream of tokens As usual with re cursive descent parsers we use several intermediate parsing function
136. Convert a string to a number Coercions between numerical types int_of_num num gt int num_of_int int gt num nat_of_num num gt nat num_of_nat nat gt num num_of_big_int big_int gt num big_int_of_num num gt big_int ratio_of_num num gt ratio num_of_ratio ratio gt num float_of_num num gt float 21 2 Module Arith_status flags that control rational arithmetic val val val val val arith_status unit gt unit Print the current status of the arithmetic flags get_error_when_null_denominator unit gt bool set_error_when_null_denominator bool gt unit Get or set the flag null_denominator When on attempting to create a rational with a null denominator raises an exception When off rationals with null denominators are accepted Initially on get_normalize_ratio unit gt bool set_normalize_ratio bool gt unit Get or set the flag normalize_ratio When on rational numbers are normalized after each operation When off rational numbers are not normalized until printed Initially off Chapter 21 The num library arbitrary precision rational arithmetic 323 val val val val val val get_normalize_ratio_when_printing unit gt bool set_normalize_ratio_when_printing bool gt unit Get or set the flag normalize_ratio_when_printing When on rational numbers are normalized before being printed When off rational numbers are printed as is without normaliza
137. D_TYPE gt SET module WrongStringSet WrongSet OrderedString module WrongStringSet sig type element WrongSet OrderedString element and set WrongSet OrderedString set val empty set val add element gt set gt set val member element gt set gt bool end WrongStringSet add gee WrongStringSet empty This expression has type string but is here used with type WrongStringSet element WrongSet OrderedString element The problem here is that SET specifies the type element abstractly so that the type equality between element in the result of the functor and t in its argument is forgotten Consequently WrongStringSet element is not the same type as string and the operations of WrongStringSet cannot be applied to strings As demonstrated above it is important that the type element in the signature SET be declared equal to Elt t unfortunately this is impossible above since SET is defined in a context where Elt does not exist To overcome this difficulty Objective Caml provides a with type construct over signatures that allows to enrich a signature with extra type equalities module AbstractSet Set functor Elt ORDERED_TYPE gt SET with type element Elt t module AbstractSet functor Elt ORDERED_TYPE gt sig type element Elt t and set val empty set val add element gt set gt set val member element gt set gt bool Chapter 4 The module system 65
138. EIVE Close for receiving SHUTDOWN_SEND Close for sending SHUTDOWN_ALL Close both The type of commands for shutdown val shutdown file_descr gt mode shutdown_command gt unit Shutdown a socket connection SHUTDOWN_SEND as second argument causes reads on the other end of the connection to return an end of file condition SHUTDOWN_RECEIVE causes writes on the other end of the connection to return a closed pipe condition SIGPIPE signal 312 val getsockname file_descr gt sockaddr Return the address of the given socket val getpeername file_descr gt sockaddr Return the address of the host connected to the given socket type msg_flag MSG_OOB MSG_DONTROUTE MSG_PEEK The flags for recv recvfrom send and sendto val recv file_descr gt buf string gt pos int gt len int gt mode msg_flag list gt int val recvfrom file_descr gt buf string gt pos int gt len int gt mode msg_flag list gt int sockaddr Receive data from an unconnected socket val send file_descr gt buf string gt pos int gt len int gt mode msg_flag list gt int val sendto file_descr gt buf string gt pos int gt len int gt mode msg_flag list gt addr sockaddr gt int Send data over an unconnected socket type socket_option SO_DEBUG Record debugging information SO_BROADCAST Permit sending of broadcast messages SO_LREUSEADDR Allow reuse of lo
139. Failure hd if the list is empty val tl a list gt a list Return the given list without its first element Raise Failure t1 if the list is empty val nth a list gt int gt a Return the n th element of the given list The first element head of the list is at position 0 Raise Failure nth if the list is too short val rev a list gt a list List reversal val append a list gt a list gt a list Catenate two lists Same function as the infix operator Not tail recursive The operator is not tail recursive either 270 val rev_append a list gt a list gt a list List rev_append 11 12 reverses 11 and catenates it to 12 This is equivalent to List rev 11 12 but rev_append is tail recursive and more efficient val concat a list list gt a list val flatten a list list gt a list Catenate flatten a list of lists Not tail recursive length of the argument length of the longest sub list Iterators val iter f a gt unit gt a list gt unit List iter f a1 an applies function f in turn to al an It is equivalent to begin f al f a2 f an end val map f a gt b gt a list gt b list List map f a1 an applies function f to a1 an and builds the list f al an with the results returned by f Not tail recursive val rev_map f a gt b gt a list g
140. It is automatically opened when a compilation starts or when the toplevel system is launched Hence it is possible to use unqualified identifiers to refer to the functions pro vided by the Pervasives module without adding a open Pervasives directive Conventions The declarations from the signature of the Pervasives module are printed one by one in typewriter font followed by a short comment All modules and the identifiers they export are indexed at the end of this report 18 1 Module Pervasives the initially opened module This module provides the built in types numbers booleans strings exceptions references lists arrays input output channels and the basic operations over these types This module is automatically opened at the beginning of each compilation All components of this module can therefore be referred by their short name without prefixing them by Pervasives Predefined types type int The type of integer numbers type char The type of characters 221 222 type type type type type type type type type string The type of character strings float The type of floating point numbers bool The type of booleans truth values unit The type of the unit value exn The type of exception values a array The type of arrays whose elements have type a a list of a a list The type of lists whose elements have type a a option
141. RootX int mutable ev_RootY int Event related information accessible in callbacks type eventField Above ButtonNumber Count Detail Focus Height KeyCode Mode OverrideRedirect Place State Time Width MouseX MouseY Char BorderWidth SendEvent KeySymString KeySymInt RootWindow SubWindow Type Widget RootX RootY In order to access the above event information one has to pass a list of required event fields to the bind function val bind events event list gt extend bool gt breakable bool gt fields eventField list action eventInfo gt unit gt a Widget widget gt unit Bind a succession of events on a widget to an action If extend is true then then binding is added after existing ones otherwise it replaces them breakable should be true when break is to be called inside the action action is called with the fields required set in an eventInfo structure Other fields should not be accessed If action is omitted then existing bindings are removed 396 val bind_class events event list gt extend bool gt breakable bool gt fields eventField list action eventInfo gt unit gt on a Widget widget gt string gt unit Same thing for all widgets of a given class If a widget is given with label on the binding will be removed as soon as it is destroyed v
142. Stream t gt expression lt fun gt val parse_simple Genlex token Stream t gt expression lt fun gt Composing the lexer and parser we finally obtain a function to read an expression from a character string let read_expr s parse_expr lexer Stream of_string s val read_expr string gt expression lt fun gt read_expr 2 x y expression Prod Const 2 000000 Sum Var x Var y 1 9 Standalone Caml programs All examples given so far were executed under the interactive system Caml code can also be compiled separately and executed non interactively using the batch compilers ocamlc or ocamlopt The source code must be put in a file with extension m1 It consists of a sequence of phrases which will be evaluated at runtime in their order of appearance in the source file Unlike in interactive Chapter 1 The core language 23 mode types and values are not printed automatically the program must call printing functions explicitly to produce some output Here is a sample standalone program to print Fibonacci numbers File fib ml let rec fib n if n lt 2 then 1 else fib m 1 fib n 2 let main let arg int_of_string Sys argv 1 in print_int fib arg print_newline exit 0 main Sys argv is an array of strings containing the command line parameters Sys argv 1 is thus the first command line parameter The program above is compiled and executed with the following shell
143. The Objective Caml system release 3 00 Documentation and user s manual Xavier Leroy with Damien Doligez Jacques Garrigue Didier R my and J r me Vouillon April 27 2000 Copyright 2000 Institut National de Recherche en Informatique et en Automatique Contents I An introduction to Objective Caml 1 The core language 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 BASICS ey amie or EE E a e a he Bes ees eee eee ee e G Datatypes e son eft eno aaa a nea St daa ana ih Bn ela a wera Bo RA Functions as values 2 ee Records and variants ooa aaa ee Imperative features 2 ee EXCOPtIONS ses 3 ile oS Ae Rete oe SL Aad 2 ea el oes bel ele pode Symbolic processing of expressions 1 a Pretty printing and parsing ooa oa ee Standalone Caml programs ooa a a 2 Labels and variants 2 1 2 2 Eabels sis fe Be hn BN he eR ee 8 en ee Oe Ee Roe te ed Polymorphic variants sai 242 28 4 e290 SASS ee ee ee 3 Objects in Caml 3 1 3 2 3 3 3 4 3 5 3 6 3 7 3 8 3 9 3 10 3 11 3 12 3 13 3 14 3 15 Classes and Objects uis don the p i paia g it Deed Gh Dg a Letom BRS Reference to self i os Be i a eee Be te ee el we Ra Se Tiitializers 2 aa OS Bake ht sein Gee a te wh Re BE Se Ee ce Mirtial methods amp 4 3 25 Se ao ei ee ES ee a a Be Ge a Re he Private methods 4 2 00 22 s 408 a ae AO ee EE we Bee tee a he es ClASSAMLCEIACES je 84 x Yt te Uh et gh Ae ek oo ke oe ae hk Ok A Inheritance os
144. The zero tagged block returned by alloc_array f a is filled with the values returned by the successive calls to f This function must not be used to build an array of floating point numbers copy_string_array p allocates an array of strings copied from the pointer to a string array p a char Low level interface The following functions are slightly more efficient than alloc but also much more difficult to use From the standpoint of the allocation functions blocks are divided according to their size as zero sized blocks small blocks with size less than or equal to Max_young_wosize and large blocks with size greater than Max_young_wosize The constant Max_young_wosize is declared in the Chapter 17 Interfacing C with Objective Caml 203 include file mlvalues h It is guaranteed to be at least 64 words so that any block with constant size less than or equal to 64 can be assumed to be small For blocks whose size is computed at run time the size must be compared against Max_young_wosize to determine the correct allocation procedure e alloc_small n t returns a fresh small block of size n lt Max_young_wosize words with tag t If this block is a structured block i e ift lt No_scan_tag then the fields of the block initially containing garbage must be initialized with legal values using direct assignment to the fields of the block before the next allocation e alloc_shr n t returns a fresh block of size n with
145. Unlike constructed values variant values taking several arguments are not flattened That is VConstr v v is represented by a block of size 2 whose field number 1 contains the representation of the pair v v but not as a block of size 3 containing v and v in fields 1 and 2 17 4 Operations on values 17 4 1 Kind tests e Is_long v is true if value v is an immediate integer false otherwise e Is_block v is true if value v is a pointer to a block and false if it is an immediate integer Chapter 17 Interfacing C with Objective Caml 201 17 4 2 Operations on integers Val_long returns the value encoding the long int l Long_val v returns the long int encoded in value v Val_int i returns the value encoding the int i Int_val v returns the int encoded in value v Val_bool xz returns the Caml boolean representing the truth value of the C integer z Bool_val v returns 0 if v is the Caml boolean false 1 if vis true Val_true Val_false represent the Caml booleans true and false 17 4 3 Accessing blocks Wosize_val v returns the size of the block v in words excluding the header Tag_val v returns the tag of the block v Field v n returns the value contained in the nt field of the structured block v Fields are numbered from 0 to Wosize_val v 1 Store_field b n v stores the value v in the field number n of value b which must be a structured block Code_val v returns the code part of the c
146. _aliases string array h_addrtype socket_domain h_addr_list inet_addr array Structure of entries in the hosts database type protocol_entry p_name string p_aliases string array p_proto int Structure of entries in the protocols database type service_entry s_name string s_aliases string array S_port int s_proto string Structure of entries in the services database val gethostname unit gt string Return the name of the local host 314 val val val val val val gethostbyname string gt host_entry Find an entry in hosts with the given name or raise Not_found gethostbyaddr inet_addr gt host_entry Find an entry in hosts with the given address or raise Not_found getprotobyname string gt protocol_entry Find an entry in protocols with the given name or raise Not_found getprotobynumber int gt protocol_entry Find an entry in protocols with the given protocol number or raise Not_found getservbyname string gt protocol string gt service_entry Find an entry in services with the given name or raise Not_found getservbyport int gt protocol string gt service_entry Find an entry in services with the given service number or raise Not_found Terminal interface The following functions implement the POSIX standard terminal interface They provide control over asynchronous communication ports and pseudo terminals Refer to the termios man
147. a Bae a EE AN a ees ype expressions rs gs eae Se a EL a ee ek eS Constants at bp bag Gem Sect She dB ies Pe ee She ene fae Se Mela seeds Bocas ee ee hts Patterns 36S ea Be dsera a he Pag gl acd Se eas EE hee Phe ee ak ee es ES XPLeSS1ONS sir Arem men Se oh Bleck gee ek ee eo RO eas ad Gk ee Type and exception definitions osoo o ee Classes tig My a E GR te a Seng yar eee Gt AE wt ee Rae eae Module types module specifications 2 2 a e a Module expressions module implementations o ooo Compilation Units e soes osa e a a ae EAR a a ee ee a e a aa a 7 Language extensions 7 1 7 2 7 3 7 4 7 5 7 6 Streams and stream parsers 1 a Range patterns soe hoc ee ee eo ee ee ee oe a Assertion checking ee Deferred computations oaoa ee Record copy with update scc coa ee Local mod le rie fs ok doth Baa ia OE ee De ae Se II The Objective Caml tools 8 Batch compilation ocamlc 8 1 8 2 8 3 8 4 Overview of the compiler ooa ee Options un hae el Mie ee Dead Bw pa leds ele lh copes Bak d Modules and the filesystem oaa a COMMON errors ee eos gk Bote ee a ba a oe A ee a et EO 59 59 60 61 63 65 67 67 73 79 83 85 85 89 90 93 95 96 99 109 111 117 121 124 125 125 126 127 127 127 127 129 9 The toplevel system ocaml 9 1 9 2 9 3 9 4 9 5 9 6 ODORS siete Bac Said acs Cems a a Seat By he oa SPS Mahe Scie a a ap Keke hoe e ana Dated Aa aee Be
148. a array Array make n x returns a fresh array of length n initialized with x All the elements of this new array are initially physically equal to x in the sense of the predicate Consequently if x is mutable it is shared among all elements of the array and modifying x through one of the array entries will modify all other entries at the same time Raise Invalid_argument ifn lt 0 orn gt Sys max_array_length If the value of x isa floating point number then the maximum size is only Sys max_array_length 2 Array create is a deprecated alias for Array make Chapter 19 The standard library 241 val init int gt f int gt a gt a array Array init n f returns a fresh array of length n with element number i initialized to the result of f i In other terms Array init n f tabulates the results of f applied to the integers O to n 1 val make_matrix dimx int gt dimy int gt a gt a array array val val val val val val val create_matrix dimx int gt dimy int gt a gt a array array Array make_matrix dimx dimy e returns a two dimensional array an array of arrays with first dimension dimx and second dimension dimy All the elements of this new matrix are initially physically equal to e The element x y of a matrix m is accessed with the notation m x y Raise Invalid_argument if dimx or dimy is less than 1 or greater than Sys max_array_length If the value of e is a
149. a deriv function that takes any float function as argument and returns an approximation of its derivative function let deriv f dx function x gt f x dx f x dx val deriv float gt float gt float gt float gt float lt fun gt let sin deriv sin ie 6 val sin float gt float lt fun gt sin pi float 1 000000 Even function composition is definable let compose f g function x gt f g x val compose a gt b gt c gt a gt c gt b lt fun gt let cos2 compose square cos val cos2 float gt float lt fun gt 14 Functions that take other functions as arguments are called functionals or higher order functions Functionals are especially useful to provide iterators or similar generic operations over a data structure For instance the standard Caml library provides a List map functional that applies a given function to each element of a list and returns the list of the results List map function n gt n 2 1 0 1 2 3 4 int list 1 3 5 7 9 This functional along with a number of other list and array functionals is predefined because it is often useful but there is nothing magic with it it can easily be defined as follows let rec map f 1 match 1 with 0 gt 0O hd tl gt f hd map f tl val map a gt b gt a list gt b list lt fun g
150. ached to the defined nonterminal The semantic actions can access the semantic attributes of the symbols in the right hand side of the rule with the notation 1 is the attribute for the first leftmost symbol 2 is the attribute for the second symbol etc The rules may contain the special symbol error to indicate resynchronization points as in yacc Actions occurring in the middle of rules are not supported 12 4 4 Error handling Error recovery is supported as follows when the parser reaches an error state no grammar rules can apply it calls a function named parse_error with the string syntax error as argument The default parse_error function does nothing and returns thus initiating error recovery see below The user can define a customized parse_error function in the header section of the grammar file The parser also enters error recovery mode if one of the grammar actions raises the Parsing Parse_error exception In error recovery mode the parser discards states from the stack until it reaches a place where the error token can be shifted It then discards tokens from the input until it finds three suc cessive tokens that can be accepted and starts processing with the first of these If no state can be uncovered where the error token can be shifted then the parser aborts by raising the Parsing Parse_error exception Refer to documentation on yacc for more details and guidance in how to use error recovery 12 5 Options Th
151. acter denoted backslash single quote n linefeed LF r return CR t horizontal tabulation TAB b backspace BS ddd the character with ASCII code ddd in decimal String literals string literal string character regular char A n t b r 0 9 0 9 0 9 string character String literals are delimited by double quote characters The two double quotes enclose a sequence of either characters different from and or escape sequences from the table below Sequence Character denoted backslash double quote n linefeed LF r return CR t horizontal tabulation TAB b backspace BS ddd the character with ASCII code ddd in decimal To allow splitting long string literals across lines the sequence newline blanks a at end of line followed by any number of blanks at the beginning of the next line is ignored inside string literals The current implementation places no restrictions on the length of string literals Naming labels To avoid ambiguities naming labels cannot just be defined syntactically as the sequence of the three tokens ident and and have to be defined at the lexical level label a z letter 0 9 _ 7 a z letter 0 9 _ optlabel Naming labels come in two flavours label for normal arguments and optlabel for optional ones They are simply distinguished by their first character eithe
152. ags are known with their associated types and they can all be present Its structure is fully known Chapter 6 The Objective Caml language 95 The second case describes a polymorphic variant value it gives the list of all tags the value could take with their associated types This type is still compatible with a variant type containing more tags The third case is the type with no information nothing is known about which tags the variant is allowed to use It only says that this must be a variant The fourth case is the most general one It gives information about all the possible tags and their associated types whether more tags are allowed or not with the ellipsis and which tags are known to potentially appear in values Full specification of variant tags are only used in this last form They can be understood as a conjunctive type for the argument it is intended to have all the types enumerated in the specification If the first ampersand amp appears just after the tag name or no type at all is given then no argument is allowed Such conjunctive constraints may be unsatisfiable In such a case the corresponding tag may not be used in a value of this type This does not mean that the whole type is not valid one can still use other available tags Object types An object type lt method type method type gt is a record of method types The type lt method type method type gt is the type of an object wi
153. ajor unit gt unit Finish the current major collection cycle 258 val val val val val full_major unit gt unit Finish the current major collection cycle and perform a complete new cycle This will collect all currently unreachable blocks compact unit gt unit gc_compaction Perform a full major collection and compact the heap Note that heap compaction is a lengthy operation print_stat out_channel gt unit Print the current values of the memory management counters in human readable form into the channel argument allocated_bytes unit gt int Return the total number of bytes allocated since the program was started Warning on 32 bit machines this counter can easily overflow and roll over finalise a gt unit gt a gt unit Gc finalise f v registers f as a finalisation function for v v must be heap allocated f will be called with v as argument at some point between the first time v becomes unreachable and the time v is collected by the GC Several functions can be registered for the same value or even several instances of the same function Each instance will be called once or never if the program terminates before the GC deallocates v A number of pitfalls are associated with finalised values finalisation functions are called asynchronously sometimes even during the execution of other finalisation functions In a multithreaded program finalisation functions a
154. al lt obj gt Closing an account can be done with the following polymorphic function let close c c withdraw c balance val close lt balance a withdraw a gt b gt gt b lt fun gt Of course this applies to all sorts of accounts Finally we gather several versions of the account into a module Account abstracted over some currency let today 01 01 2000 an approximation module Account M MONEY struct type m M c let m new M c let zero m 0 Chapter 5 Advanced examples with classes and modules class bank object self val mutable balance zero method balance balance val mutable history method private trace x history lt x history method deposit x self trace Deposit x if zero leq x then balance lt balance plus x else raise Invalid_argument deposit method withdraw x if x leq balance then else zero method history List rev history end class type client_view object method deposit m gt unit method history m operation list method withdraw m gt m method balance m end class virtual check_client x let y if m 100 leq x then x else raise Failure Insufficient initial deposit in object self initializer self deposit y end module Client B sig class bank client_view end struct class account x client_view object inherit B bank inherit check_client x end let discount x let c
155. al bind_tag events event list gt extend bool gt breakable bool gt fields eventField list action eventInfo gt unit gt on a Widget widget gt string gt unit Same thing for all widgets having a given tag val break unit gt unit Used inside a bound action do not call other actions after this one This is only possible if this action was bound with breakable true Chapter 28 The bigarray library The bigarray library implements large multi dimensional numerical arrays These arrays are called big arrays to distinguish them from the standard Caml arrays described in section 19 2 The main differences between big arrays and standard Caml arrays are as follows Big arrays are not limited in size unlike Caml arrays float array are limited to 2097151 elements on a 32 bit platform other array types to 4194303 elements Big arrays are multi dimensional Any number of dimensions between 1 and 16 is supported In contrast Caml arrays are mono dimensional and require encoding multi dimensional arrays as arrays of arrays Big arrays can only contain integers and floating point numbers while Caml arrays can contain arbitrary Caml data types However big arrays provide more space efficient storage of integer and floating point elements in particular because they support small types such as single precision floats and 8 and 16 bit integers in addition to the standard Caml types of dou
156. ality test Physical equality test l Physical inequality test lt Test less than lt Test less than or equal gt Test greater than gt Test greater than or equal 6 7 5 Objects Object creation When class path evaluates to a class body new class path evaluates to an object containing the instance variables and methods of this class When class path evaluates to a class function new class path evaluates to a function expecting the same number of arguments and returning a new object of this class Chapter 6 The Objective Caml language 109 Message sending The expression expr method name invokes the method method name of the object denoted by expr Coercion The type of an object can be coerced weakened to a _ supertype The expression expr gt typexpr coerces the expression expr to type typexpr The expression expr typexpr gt typexprs coerces the expression expr from type typexpr to type typexprs The former operator will sometimes fail to coerce an expression expr from a type t to a type tg even if type t is a subtype of type t2 In this case the latter operator should be used In a class definition coercion to the type this class defines is the identity as this type abbrevi ation is not yet completely defined Object duplication An object can be duplicated using the library function Oo copy see section 19 20 Inside a method the expression
157. all pending text is displayed val print_newline unit gt unit Equivalent to print_flush followed by a new line val force_newline unit gt unit Force a newline in the current box Not the normal way of pretty printing you should prefer break hints val print_if_newline unit gt unit Execute the next formatting command if the preceding line has just been split Otherwise ignore the next formatting command Margin val set_margin int gt unit set_margin d sets the value of the right margin to d in characters this value is used to detect line overflows that leads to split lines Nothing happens if d is smaller than 2 or bigger than 999999999 val get_margin unit gt int Return the position of the right margin Maximum indentation limit val set_max_indent int gt unit set_max_indent d sets the value of the maximum indentation limit to d in characters once this limit is reached boxes are rejected to the left if they do not fit on the current line Nothing happens if d is smaller than 2 or bigger than 999999999 val get_max_indent unit gt int Return the value of the maximum indentation limit in characters Formatting depth maximum number of boxes allowed before ellipsis val set_max_boxes int gt unit set_max_boxes max sets the maximum number of boxes simultaneously opened Material inside boxes nested deeper is printed as an ellipsis more precisely as the text retur
158. alue of identifier at point C c C d command display display value of identifier at point C c C r command run execute the program forward to next breakpoint C c C v command reverse execute the program backward to latest breakpoint C c C 1 command last go back one step in the command history C c C t command backtrace display backtrace of function calls C c C f command finish run forward till the current function returns C c lt command up select the stack frame below the current frame C c gt command down select the stack frame above the current frame In all buffers in Caml editing mode the following debugger commands are also available C x C a C b command break set a breakpoint at event closest to point Chapter 15 The debugger ocamldebug 187 C x C a C p command print print value of identifier at point C x C a C d command display display value of identifier at point 188 Chapter 16 Profiling ocamlprof This chapter describes how the execution of Objective Caml programs can be profiled by recording how many times functions are called branches of conditionals are taken 16 1 Compiling for profiling Before profiling an execution the program must be compiled in profiling mode using the ocamlcp front end to the ocamlc compiler see chapter 8 When compiling modules separately ocamlcp must be used when compiling the modules production of cmo files and
159. ame name module type name module type module type instead of module module name functor name module type gt gt module type Module type specifications A module type component of a signature can be specified either as a manifest module type or as an abstract module type An abstract module type specification module type modtype name allows the name modtype name to be implemented by any module type in a matching signature but hides the implementation of the module type to all users of the signature A manifest module type specification module type modtype name module type requires the name modtype name to be implemented by the module type module type in a matching signature but makes the equality between modtype name and module type apparent to all users of the signature Opening a module path The expression open module path in a signature does not specify any components It simply affects the parsing of the following items of the signature allowing components of the module denoted by module path to be referred to by their simple names name instead of path accesses module path name The scope of the open stops at the end of the signature expression Including a signature The expression include modtype path in a signature performs textual inclusion of the components of the signature denoted by modtype path It behaves as if the components of the included signature were copied at the location of the
160. ame extended module path capitalized ident extended module path extended module path modtype path modtype name extended module path ident class path class name module path lowercase ident A named object can be referred to either by its name following the usual static scoping rules for names or by an access path prefix name where prefix designates a module and name is the name of an object defined in that module The first component of the path prefix is either a simple module name or an access path name name2g in case the defining module is itself nested inside other modules For referring to type constructors or module types the prefix can also contain simple functor applications as in the syntactic class extended module path above in case the defining module is the result of a functor application Label names tag names method names and instance variable names need not be qualified the Chapter 6 The Objective Caml language 93 former three are global labels while the latter are local to a class 6 4 Type expressions typexpr i method type tag list gt ident typexpr ident typexpr gt typexpr typexpr typexpr typeconstr typexpr typeconstr typexpr typexpr typeconstr typexpr as ident L variant type lt gt lt method type method type gt class path typexpr class path typexpr typexpr class path
161. ame string and the source and destination chunks overlap Raise Invalid_argument if srcoff and len do not designate a valid substring of src or if dstoff and len do not designate a valid substring of dst concat sep string gt string list gt string String concat sep sl catenates the list of strings s1 inserting the separator string sep between each escaped string gt string Return a copy of the argument with special characters represented by escape sequences following the lexical conventions of Objective Caml 290 val val val val val val val val val val val index string gt char gt int String index s c returns the position of the leftmost occurrence of character c in string s Raise Not_found if c does not occur in s rindex string gt char gt int String rindex s c returns the position of the rightmost occurrence of character c in string s Raise Not_found if c does not occur in s index_from string gt int gt char gt int rindex_from string gt int gt char gt int Same as String index and String rindex but start searching at the character position given as second argument String index s c is equivalent to String index_from s 0 c and String rindex s c to String rindex_from s String length s 1 c contains string gt char gt bool String contains s c tests if character c appears in the string s contains_from string gt int gt char gt
162. amlrun If caml out is the name of the file produced by the linking phase the command ocamlrun caml out arg argg TOn executes the compiled code contained in caml out passing it as arguments the character strings arg to arg See chapter 10 for more details On most Unix systems the file produced by the linking phase can be run directly as in caml out arg argo argn The produced file has the executable bit set and it manages to launch the bytecode interpreter by itself 8 2 Options The following command line options are recognized by ocamlc a Build a library cma file with the object files cmo files given on the command line instead of linking them into an executable file The name of the library can be set with the o option The default name is library cma If custom cclib or ccopt options are passed on the command line these options are stored in the resulting cma library Then linking with this library automatically adds back the custom cclib and ccopt options as if they had been provided on the command line unless the noautolink option is given c Compile only Suppress the linking phase of the compilation Source code files are turned into compiled files but no executable file is produced This option is useful to compile modules separately cc ccomp Use ccomp as the C linker called by ocamlc custom and as the C compiler for compiling c source files Chapter 8 Batch compilation o
163. ample Constructed term Representation O Val_int 0 false Val_int 0 true Val_int 1 Val_int 0 h t Block with size 2 and tag 0 first field con tains h second field t As a convenience caml mlvalues h defines the macros Val_unit Val_false and Val_true to refer to false and true 17 3 5 Objects Objects are represented as zero tagged blocks The first field of the block refers to the object class and associated method suite in a format that cannot easily be exploited from C The remaining fields of the object contain the values of the instance variables of the object Instance variables are stored in the order in which they appear in the class definition taking inherited classes into account 17 3 6 Variants Like constructed terms values of variant types are represented either as integers for variants without arguments or as blocks for variants with an argument Unlike constructed terms variant constructors are not numbered starting from 0 but identified by a hash value a Caml integer as computed by the C function hash_variant declared in lt caml mlvalues h gt the hash value for a variant constructor named say VConstr is hash_value VConstr The variant value VConstr is represented by hash_value VConstr The variant value vVConstr v is represented by a block of size 2 and tag 0 with field number 0 containing hash_value VConstr and field number 1 containing v
164. ams val allow_unsafe_modules bool gt unit Govern whether unsafe object files are allowed to be dynamically linked A compilation unit is unsafe if it contains declarations of external functions which can break type safety By default dynamic linking of unsafe object files is not allowed type linking_error Undefined_global of string Unavailable_primitive of string type error Not_a_bytecode_file of string Inconsistent_import of string Unavailable_unit of string Unsafe_file Linking_error of string linking error Corrupted_interface of string exception Error of error Errors in dynamic linking are reported by raising the Error exception with a description of the error val error_message error gt string Convert an error description to a printable message Chapter 27 The LablTk library Tcl Tk GUI interface The labltk library provides access to the Tcl Tk GUI from Objective Caml programs This interface is generated in an automated way and you should refer to Tcl Tk books and man pages for detailed information on the behavior of the numerous functions Programs that use the lab1tk library must be linked as follows ocamlc other options I labltk dir labltk cma other files ocamlopt other options I labltk dir labltk cmxa other files labltk dir is CAMLLIB labltk On Unix the default location is usr local lib caml labltk Unix The lab1tk library is available for any system with Tcl Tk installed st
165. an simply link with mylib cma ocamlc o myprog mylib cma and the system will automatically add the custom and cclib lmylib options achieving the same effect as ocamlc o myprog custom a cmo b cmo cclib lmylib The alternative of course is to build the library without extra options ocamlc o mylib cma a cmo b cmo and then ask users to provide the custom and cclib lmylib options themselves at link time ocamlc o myprog custom mylib cma cclib lmylib The former alternative is more convenient for the final users of the library however 17 1 4 Building standalone custom runtime systems It is sometimes inconvenient to build a custom runtime system each time Caml code is linked with C libraries like ocamlc custom does For one thing the building of the runtime system is slow on some systems that have bad linkers or slow remote file systems for another thing the platform independence of bytecode files is lost forcing to perform one ocamlc custom link per platform of interest An alternative to ocamlc custom is to build separately a custom runtime system integrating the desired C libraries then generate pure bytecode executables not containing their own run time system that can run on this custom runtime This is achieved by the make_runtime and use_runtime flags to ocamlc For example to build a custom runtime system integrating the C parts of the unix and threads libraries do ocam
166. and is therefore reasonably efficient insertion and membership take time logarithmic in the size of the set for instance module type OrderedType sig type t val compare t gt t gt int end The input signature of the functor Set Make t is the type of the set elements compare is a total ordering function over the set elements This is a two argument function f such that f e1 e2 is zero if the elements e1 and e2 are equal f e1 e2 is strictly negative if e1 is smaller than e2 and f e1 e2 is strictly positive if e1 is greater than e2 Example a suitable ordering function is the generic structural comparison function compare 284 module type S sig type elt The type of the set elements type t The type of sets val empty t The empty set val is_empty t gt bool Test whether a set is empty or not val mem elt gt t gt bool mem x s tests whether x belongs to the set s val add elt gt t gt t add x s returns a set containing all elements of s plus x If x was already in s s is returned unchanged val singleton elt gt t singleton x returns the one element set containing only x val remove elt gt t gt t remove x s returns a set containing all elements of s except x If x was not in s s is returned unchanged val union t gt t gt t val inter t gt t gt t val diff t gt t gt t Union intersection and set difference val compare t gt t gt int Total ordering
167. and wait_write but wait for at most the amount of time given as second argument in seconds Return true if the file descriptor is ready for input output and false if the timeout expired val select read Unix file_descr list gt write Unix file_descr list gt exn Unix file_descr list gt timeout float gt Unix file_descr list Unix file_descr list Unix file_descr list Suspend the execution of the calling thead until input output becomes possible on the given Unix file descriptors The arguments and results have the same meaning as for Unix select val wait_pid int gt int Unix process_status wait_pid p suspends the execution of the calling thread until the Unix process specified by the process identifier p terminates A pid p of 1 means wait for any child A pid of 0 means wait for any child in the same process group as the current process Negative pid arguments represent process groups Returns the pid of the child caught and its termination status as per Unix wait val wait_signal int list gt int wait_signal sigs suspends the execution of the calling thread until the process receives one of the signals specified in the list sigs It then returns the number of the signal received Signal handlers attached to the signals in sigs will not be invoked Do not call wait_signal concurrently from several threads on the same signals val yield unit gt unit Re schedule the calling thread without suspending it Th
168. anscript of a session with the interactive system lines starting with represent user input the system responses are printed below without a leading Under the interactive system the user types Caml phrases terminated by in response to the prompt and the system compiles them on the fly executes them and prints the outcome of evaluation Phrases are either simple expressions or let definitions of identifiers either values or functions 1 2 3 int 7 let pi 4 0 atan 1 0 val pi float 3 141593 let square x X Xj val square float gt float lt fun gt square sin pi square cos pi float 1 000000 The Caml system computes both the value and the type for each phrase Even function parameters need no explicit type declaration the system infers their types from their usage in the function Notice also that integers and floating point numbers are distinct types with distinct operators and operate on integers but and operate on floats 1 0 25 This expression has type float but is here used with type int 11 12 Recursive functions are defined with the let rec binding let rec fib n if n lt 2 then 1 else fib n 1 fib n 2 val fib int gt int lt fun gt fib 10 int 89 1 2 Data types In addition to integers and floating point numbers Caml offers the usual basic data types booleans characters and character strings
169. apter 17 Interfacing C with Objective Caml 199 Caution if a pointer returned by malloc is cast to the type value and returned to Caml explicit deallocation of the pointer using free is potentially dangerous because the pointer may still be accessible from the Caml world Worse the memory space deallocated by free can later be reallocated as part of the Caml heap the pointer formerly pointing outside the Caml heap now points inside the Caml heap and this can confuse the garbage collector To avoid these problems it is preferable to wrap the pointer in a Caml block with tag Abstract_tag or Custom_tag 17 3 Representation of Caml data types This section describes how Caml data types are encoded in the value type 17 3 1 Atomic types Caml type Encoding int Unboxed integer values char Unboxed integer values ASCII code float Blocks with tag Double_tag string Blocks with tag String_tag int32 Blocks with tag Custom_tag int64 Blocks with tag Custom_tag nativeint Blocks with tag Custom_tag 17 3 2 Tuples and records Tuples are represented by pointers to blocks with tag 0 Records are also represented by zero tagged blocks The ordering of labels in the record type declaration determines the layout of the record fields the value associated to the label declared first is stored in field 0 of the block the value associated to the label declared next goes in field 1 and so on As an optimization recor
170. aracters Chapter 19 The standard library 247 19 8 Module Format pretty printing This module implements a pretty printing facility to format text within pretty printing boxes The pretty printer breaks lines at specified break hints and indents lines according to the box structure You may consider this module as providing an extension to the printf facility to provide automatic line breaking The addition of pretty printing annotations to your regular printf formats gives you fancy indentation and line breaks Pretty printing annotations are described below in the documentation of the function fprintf You may also use the explicit box management and printing functions provided by this module This style is more basic but more verbose than the fprintf concise formats For instance the sequence open_box print_string x print_space print_int 1 close_box that prints x 1 within a pretty printing box can be abbreviated as printf s i x 1 Rule of thumb for casual users of this library use simple boxes as obtained by open_box 0 use simple break hints as obtained by print_cut that outputs a simple break hint or by print_space that outputs a space indicating a break hint once a box is opened display its material with basic printing functions e g print_int and print_string when the material for a box has been printed call close_box to close the box at the end of your routine
171. ariant values not belonging explicitly to a predefined variant type and following specific typing rules They can be either constant written tag name or non constant written tag name v 6 2 7 Functions Functional values are mappings from values to values 6 2 8 Objects Objects are composed of a hidden internal state which is a record of instance variables and a set of methods for accessing and modifying these variables The structure of an object is described by the toplevel class that created it 6 3 Names Identifiers are used to give names to several classes of language objects and refer to these objects by name later e value names syntactic class value name e value constructors constant class cconstr name or non constant class ncconstr name e labels label name e variant tags tag name Chapter 6 The Objective Caml language 91 e type constructors typeconstr name e record fields field name e class names class name e method names method name e instance variable names inst var name e module names module name e module type names modtype name These nine name spaces are distinguished both by the context and by the capitalization of the identifier whether the first letter of the identifier is in lowercase written lowercase ident below or in uppercase written capitalized ident Underscore is considered a lowercase letter for this purpose Naming objects va
172. arting from Tcl 7 5 Tk 4 1 up to Tcl Tk 8 3 Beware that some beta versions may have compatibility problems If the library was not compiled correctly try to run again the configure script with the option tkdefs switches where switches is a list of C style inclusion paths leading to the right tcl h and tk h for instance I usr local include tcl8 0 I usr local include tk8 0 A script is installed to make easier the use of the labltk library as toplevel labltk This is a toplevel including the labl1tk library and the path is already set as to allow the use of the various modules It also includes code for the Unix and Str libraries You can use it in place of ocaml Windows The labltk library has been precompiled for use with Tcl Tk 8 0 You must first have it installed on your system It can be downloaded from http www scriptics com products tcltk 8 0 html After installing it you must put the dynamically loaded libraries tc180 d11 and tk80 d11 from the bin directory of the Tcl installation in a directory included in you path The toplevel including Unix and Str is available as labltk But you need to explicitly add the labltk library directory to your load path with the directory directive 301 302 The lab1tk library is composed of a large number of modules Bell Imagebitmap Place Button Imagephoto Radiobutton Canvas Label Scale Checkbutton Listbox Scrollbar Clipboard Menu Selection Dialog Menubutton Text Entr
173. as such with no possibility for further personalization It is important that to provide the client s view as a functor Client so that client accounts can still be build after a possible specialization of the bank The functor Client may remain unchanged and be passed the new definition to initialize a client s view of the extended account module Investment_account M MONEY struct type m M c module A Account M class bank object inherit A bank as super method deposit x if mew M c 1000 leq x then print_string Would you like to invest super deposit x end module Client A Client end The functor Client may also be redefined when some new features of the account can be given to the client module Internet_account M MONEY struct type m M c module A Account M Chapter 5 Advanced examples with classes and modules 73 class bank object inherit A bank method mail s print_string s end class type client_view object method deposit m gt unit method history m operation list method withdraw m gt m method balance m method mail string gt unit end module Client B sig class bank client_view end struct class account x client_view object inherit B bank inherit A check_client x end end HHH HH HH HH HH HHH HH HHHH end 5 2 Simple modules as classes One may wonder whether it is possible to
174. ass subject window_observer object inherit subject event observer method notify s e s draw end class a window_observer object constraint a lt draw unit gt method notify a gt event gt unit end Unsurprisingly the type of window is recursive let window new window_subject Chapter 5 Advanced examples with classes and modules 81 val window lt notify a gt event gt unit _ gt window_subject as a lt obj gt However the two classes of window_subject and window_observer are not mutually recursive let window_observer new window_observer val window_observer lt draw unit _ gt window_observer lt obj gt window add_observer window_observer unit window move 1 Position 1 unit Classes window_observer and window_subject can still be extended by inheritance For in stance one may enrich the subject with new behaviors and refined the behavior of the observer class observer richer_window_subject object self inherit observer window_subject val mutable size 1 method resize x size lt size x self notify_observers Resize val mutable top false method raise top lt true self notify_observers Raise method draw Printf printf Position d Size d n position size end class a richer_window_subject object b constraint a lt notify
175. ates the file corresponding to the given descriptor to the given size File statistics type file_kind S_REG Regular file S_DIR Directory S_CHR Character device S_BLK Block device S_LNK Symbolic link S_FIFO Named pipe S_SOCK Socket type stats st_dev int Device number st_ino int Inode number st_kind file_kind Kind of the file st_perm file_perm Access rights st_nlink int Number of links st_uid int User id of the owner st_gid int Group id of the owner st_rdev int Device minor number st_size int Size in bytes st_atime float Last access time st_mtime float Last modification time st_ctime float Last status change time The informations returned by the stat calls 302 val stat string gt stats Return the information for the named file val lstat string gt stats Same as stat but in case the file is a symbolic link return the information for the link itself val fstat file_descr gt stats Return the information for the file associated with the given descriptor Operations on file names val unlink string gt unit Removes the named file val rename src string gt dst string gt unit rename old new changes the name of a file from old to new val link src string gt dst string gt unit link source dest creates a hard link named des
176. ations one will most often describe fixed variant types that is types that can be no longer refined This is also the case for type abbreviations Such types do not contain lt or gt but just an enumeration of the tags and their associated types just like in a normal datatype definition For conciseness of is omitted in polymorphic variant types type a vlist Nil Cons of a a vlist 32 type a vlist Nil Cons of a a vlist let rec map f a vlist gt b vlist function Nil gt Nil Cons a 1 gt Cons f a map f 1 55 val map f a gt b gt a vlist gt b vlist lt fun gt Advanced use Type checking polymorphic variants is a subtle thing and some expressions may result in more complex type information function A gt B x gt x lt x B Al gt B as a gt a lt fun gt Here the means that we know that A and B may not have an argument but there is no specified upper bound on the number of variant tags in this variant type We know also that B can appear in the result and input and output types have to be kept equal because x is returned as is let f1 function A x gt x 1 B gt true C gt false let f2 function A x gt x a B gt true val f1 lt A of int B C gt bool lt fun gt val f2 lt
177. ayout c val create kind a b kind gt layout c layout gt dimi int gt dim2 int gt dim3 int gt a b c t Array3 create kind layout dim1 dim2 dim3 returns a new bigarray of three dimension whose size is dim1 in the first dimension dim2 in the second dimension and dim3 in the third kind and layout determine the array element kind and the array layout as described for Genarray create Chapter 28 The bigarray library 367 val dimi a b c t gt int Return the first dimension of the given three dimensional big array val dim2 a b c t gt int Return the second dimension of the given three dimensional big array val dim3 a b c t gt int Return the third dimension of the given three dimensional big array external get a b c t gt int gt int gt int gt a Array3 get a x y z also written a x y z returns the element of a at coordinates x y z x y and z must be within the bounds of a as described for Genarray get otherwise Invalid_arg is raised external set a b c t gt int gt int gt int gt a gt unit Array3 set a x y v or alternatively a x y z lt v stores the value v at coordinates x y z in a x y and z must be within the bounds of a as described for Genarray set otherwise Invalid_arg is raised external sub_left Ca b c_layout t gt pos int gt len int gt a b
178. b gt unit but its first argument is labeled data 2 1 2 Optional arguments An interesting feature of labeled arguments is that they can be made optional For optional parameters the question mark replaces the tilde of non optional ones and the label is also prefixed by in the function type Default values may be given for such optional parameters let bump step 1 x x step val bump step int gt int gt int lt fun gt bump 2 int 83 bump step 3 2 int 5 Chapter 2 Labels and variants 27 A function taking some optional arguments must also take at least one non labeled argument This is because the criterion for deciding whether an optional has been omitted is the application on a non labeled argument appearing after this optional argument in the function type let test x 0 y 0 O z2 0 O x y 2 3 val test x int gt y int gt unit gt z int gt unit gt int int int lt fun gt test z int gt unit gt int int int lt fun gt test x 2 72 3 Q int int int 2 0 3 Optional arguments behave similarly in classic and commuting label mode Omitting the label of an optional argument is not allowed and in both cases commutation between differently labeled optional arguments may occur test y 2 x 3 O Oss int int int 3 2 0 Optional arguments are actually implemented as option type
179. ble precision floats and 32 and 64 bit integers The memory layout of big arrays is entirely compatible with that of arrays in C and Fortran allowing large arrays to be passed back and forth between Caml code and C Fortran code with no data copying at all Big arrays support interesting high level operations that normal arrays do not provide effi ciently such as extracting sub arrays and slicing a multi dimensional array along certain dimensions all without any copying Programs that use the bigarray library must be linked as follows ocamlc other options bigarray cma other files ocamlopt other options bigarray cmxa other files For interactive use of the bigarray library do ocamlmktop o mytop bigarray cma mytop 357 358 28 1 Module Bigarray large multi dimensional numerical arrays This module implements multi dimensional arrays of integers and floating point numbers thereafter referred to as big arrays The implementation allows efficient sharing of large numerical arrays between Caml code and C or Fortran numerical libraries Concerning the naming conventions users of this module are encouraged to do open Bigarray in their source then refer to array types and operations via short dot notation e g Array1 t or Array2 sub Big arrays support all the Caml ad hoc polymorphic operations comparisons lt gt lt etc as well as compare hashing module Hash and structured input output o
180. bool String contains_from s start c tests if character c appears in the substring of s starting from start to the end of s Raise Invalid_argument if start is not a valid index of s rcontains_from string gt int gt char gt bool String rcontains_from s stop c tests if character c appears in the substring of s starting from the beginning of s to index stop Raise Invalid_argument if stop is not a valid index of s uppercase string gt string Return a copy of the argument with all lowercase letters translated to uppercase including accented letters of the ISO Latin 1 8859 1 character set lowercase string gt string Return a copy of the argument with all uppercase letters translated to lowercase including accented letters of the ISO Latin 1 8859 1 character set capitalize string gt string Return a copy of the argument with the first letter set to uppercase uncapitalize string gt string Return a copy of the argument with the first letter set to lowercase Chapter 19 The standard library 291 19 31 Module Sys system interface val val val val val val val val val val val val val val argv string array The command line arguments given to the process The first element is the command name used to invoke the program The following elements are the command line arguments given to the program file_exists string gt bool Test if a file with the given na
181. bytecode interpreter when the evaluation stack reaches its maximal size This often indicates infinite or excessively deep recursion in the user s program exception Sys_error of string Exception raised by the input output functions to report an operating system error exception End_of_file Exception raised by input functions to signal that the end of file has been reached exception Division_by_zero Exception raised by division and remainder operations when their second argument is null exception Exit This exception is not raised by any library function It is provided for use in your programs exception Sys_blocked_io A special case of Sys_error raised when no I O is possible on a non blocking I O channel val invalid_arg string gt a Raise exception Invalid_argument with the given string val failwith string gt a Raise exception Failure with the given string 224 Comparisons val val val val val val val val val val val a gt a gt bool e1 e2 tests for structural equality of e1 and e2 Mutable structures e g references and arrays are equal if and only if their current contents are structurally equal even if the two mutable objects are not the same physical object Equality between functional values raises Invalid_argument Equality between cyclic data structures may not terminate lt gt a gt a gt bool Negation of lt a gt a gt bool
182. c t gt a gt unit Fill the given big array with the given value See Genarray fill for more details val of_array kind a b kind gt layout c layout gt a array gt a b c t Build a one dimensional big array initialized from the given array val map_file Unix file_descr gt kind a b kind gt layout c layout gt shared bool gt dim int gt a b c t Memory mapping of a file as a one dimensional big array See Genarray map_file for more details end Chapter 28 The bigarray library 365 Two dimensional arrays The Array2 structure provides operations similar to those of Genarray but specialized to the case of three dimensional arrays module Array2 sig type Ca Thy c t The type of two dimensional big arrays whose elements have Caml type a representation kind b and memory layout c val create kind a b kind gt layout c layout gt diml int gt dim2 int gt a b c t Array2 create kind layout dim1 dim2 returns a new bigarray of two dimension whose size is dim1 in the first dimension and dim2 in the second dimension kind and layout determine the array element kind and the array layout as described for Genarray create val dimi a b c t gt int Return the first dimension of the given two dimensional big array val dim2 a b c t gt int Return the second dimension of the given two dimensiona
183. c function however The external function fis not available This error appears when trying to link code that calls external functions written in C in default runtime mode As explained in chapter 17 such code must be linked in custom runtime mode Fix add the custom option as well as the C libraries and C object files that implement the required external functions Chapter 9 The toplevel system ocaml This chapter describes the toplevel system for Objective Caml that permits interactive use of the Objective Caml system through a read eval print loop In this mode the system repeatedly reads Caml phrases from the input then typechecks compile and evaluate them then prints the inferred type and result value if any The system prints a sharp prompt before reading each phrase Input to the toplevel can span several lines It is terminated by a double semicolon The toplevel input consists in one or several toplevel phrases with the following syntax toplevel input toplevel phrase toplevel phrase definition expr ident directive argument definition let rec let binding and let binding external value name typexpr external declaration type definition exception definition module module name module type module expr module type modtype name module type open module path directive argument nothing string literal integer literal value path A phrase can consist of
184. c_layout t Extract a three dimensional sub array of the given three dimensional big array by restricting the first dimension See Genarray sub_left for more details Array3 sub_left applies only to arrays with C layout external sub_right Ca b fortran_layout t gt pos int gt len int gt a b fortran_layout t Extract a three dimensional sub array of the given three dimensional big array by restricting the second dimension See Genarray sub_right for more details Array3 sub_right applies only to arrays with Fortran layout val slice_left_1 Ca b c_layout t gt x int gt y int gt a b c_layout Array1 t Extract a one dimensional slice of the given three dimensional big array by fixing the first two coordinates The integer parameters are the coordinates of the slice to extract See Genarray slice_left for more details Array3 slice_left_1 applies only to arrays with C layout 368 val slice_right_1 Ca b fortran_layout t gt y int gt z int gt Ca b fortran_layout Array1 t Extract a one dimensional slice of the given three dimensional big array by fixing the last two coordinates The integer parameters are the coordinates of the slice to extract See Genarray slice_right for more details Array3 slice_right_1 applies only to arrays with Fortran layout val slice_left_2 Ca b c_layout t gt x int gt a b c_layout Array2 t Extract a two dimensional
185. cal addresses for bind SO_KEEPALIVE Keep connection active SO_DONTROUTE Bypass the standard routing algorithms SO_OOBINLINE Leave out of band data in line The socket options settable with setsockopt val getsockopt file_descr gt socket_option gt bool Return the current status of an option in the given socket val setsockopt file_descr gt socket_option gt bool gt unit Set or clear an option in the given socket Chapter 20 The unix library Unix system calls 313 High level network connection functions val open_connection sockaddr gt in_channel out_channel Connect to a server at the given address Return a pair of buffered channels connected to the server Remember to call flush on the output channel at the right times to ensure correct synchronization val shutdown_connection in_channel gt unit Shut down a connection established with open_connection that is transmit an end of file condition to the server reading on the other side of the connection val establish_server in_channel gt out_channel gt unit gt addr sockaddr gt unit Establish a server on the given address The function given as first argument is called for each connection with two buffered channels connected to the client A new process is created for each connection The function establish_server never returns normally Host and protocol databases type host_entry h_name string h
186. camlc 133 cclib llibname Pass the 1libname option to the C linker when linking in custom runtime mode see the custom option This causes the given C library to be linked with the program ccopt option Pass the given option to the C compiler and linker when linking in custom runtime mode see the custom option For instance ccopt Ldir causes the C linker to search for C libraries in directory dir custom Link in custom runtime mode In the default linking mode the linker produces bytecode that is intended to be executed with the shared runtime system ocamlrun In the custom runtime mode the linker produces an output file that contains both the runtime system and the bytecode for the program The resulting file is larger but it can be executed directly even if the ocamlrun command is not installed Moreover the custom runtime mode enables linking Caml code with user defined C functions as described in chapter 17 g Add debugging information while compiling and linking This option is required in order to be able to debug the program with ocamldebug see chapter 15 i Cause the compiler to print all defined names with their inferred types or their definitions when compiling an implementation m1 file This can be useful to check the types inferred by the compiler Also since the output follows the syntax of interfaces it can help in writing an explicit interface m1i file for a file just redi
187. camldep 13 1 13 2 PLCs x62 2a a ms e a eh ate oh LS Gooey Le EAS A typical Makefiles si ip atman eh ee oe ee le wee ed ee ee 14 The browser editor ocamlbrowser 14 1 14 2 14 3 14 4 14 5 Invocation ass ae ari gal eee ee De Bo Ee eee de MAC WET 554 Sie aeaaea Syke Soke Bok ce SO Ee Dae ara aie Be tala eg Bopp ee EE Mod le walking 222 30 2 ive dp ae tone Pe Ree Ae eae Ses Bile S itOn L422 hfe be aoe A le oS fe a aed Che ee of ec se Oe ne ek Sae asus toca ot SD eh ek es oe ee oe A ee el ee wo 8 ead coe 8 eS 15 The debugger ocamldebug 15 1 15 2 15 3 15 4 15 5 15 6 Compiling for d bueeing 2 9 wa ges ee ded a Pe RS AG oe PO Rae es a ie INVOCATION aa oa Geel Bk Oa Re ck ae BE ee Re BE a BS OR OS ES Commands i iaa aT aie See es op ead ech ees We ae wh eae eo BD es Executing a program oaos e ee Breakpoints aos esa eich doe the me ghee geal a het aAa We tele 2k ee ee A ek The call stack sirare is Me te See ene Peg Re OO Ae eo i ee Re ak 139 141 142 143 143 144 144 147 147 147 148 151 151 152 155 155 157 157 158 160 160 162 163 164 167 167 168 171 171 172 172 173 173 15 7 15 8 15 9 15 10 Examining variable values Controlling the debugger Miscellaneous commands Running the debugger under Emacs 16 Profiling ocamlprof 16 1 16 2 16 3 16 4 Compiling for profiling Profiling an
188. can also be used though this is not strictly necessary when linking them together To make sure your programs can be compiled in profiling mode avoid using any identifier that begins with __ocaml_prof The amount of profiling information can be controlled through the p option to ocamlcp followed by one or several letters indicating which parts of the program should be profiled a all options f function calls a count point is set at the beginning of function bodies i if then else count points are set in both then branch and else branch 1 while for loops a count point is set at the beginning of the loop body m match branches a count point is set at the beginning of the body of each branch t try with branches a count point is set at the beginning of the body of each branch For instance compiling with ocamlcp p film profiles function calls if then else loops and pattern matching Calling ocamlcp without the p option defaults to p fm meaning that only function calls and pattern matching are profiled Note Due to the implementation of streams and stream patterns as syntactic sugar it is hard to predict what parts of stream expressions and patterns will be profiled by a given flag To profile a program with streams we recommend using ocamlcp p a 189 190 16 2 Profiling an execution Running a bytecode executable file that has been compiled with ocamlcp records the execution counts for the spec
189. class a c object _ b val repr a list method is_empty repr method mem x List exists x repr method add x lt repr merge x repr gt method union s b lt repr merge repr s tag gt method iter f a gt unit List iter f repr method tag repr end end 5 3 The subject observer pattern The following example known as the subject observer pattern is often presented in the literature as a difficult inheritance problem with inter connected classes The general pattern amounts to the definition a pair of two classes that recursively interact with one another The class observer has a distinguished method notify that requires two arguments a subject and an event to execute an action class virtual subject event observer object method virtual notify subject gt event gt unit end class virtual a b observer object method virtual notify a gt b gt unit end The class subject remembers a list of observers in an instance variable and has a distinguished method notify_observers to broadcast the message notify to all observers with a particular event e class observer event subject object self val mutable observers observer list method add_observer obs observers lt obs observers method notify_observers e event List iter fun x gt
190. clear a t gt unit Discard all elements from a queue length a t gt int Return the number of elements in a queue iter f a gt unit gt a t gt unit iter f q applies f in turn to all elements of q from the least recently entered to the most recently entered The queue itself is unchanged Chapter 19 The standard library 283 19 25 Module Random pseudo random number generator val init int gt unit Initialize the generator using the argument as a seed The same seed will always yield the same sequence of numbers val full_init int array gt unit Same as init but takes more data as seed val self_init unit gt unit Initialize the generator with a more or less random seed chosen in a system dependent way val bits unit gt int Return 30 random bits in a nonnegative integer val int int gt int Random int bound returns a random integer between 0 inclusive and bound exclusive bound must be more than 0 and less than 227 val float float gt float Random float bound returns a random floating point number between 0 inclusive and bound exclusive If bound is negative the result is negative If bound is 0 the result is 0 19 26 Module Set sets over ordered types This module implements the set data structure given a total ordering function over the set elements All operations over sets are purely applicative no side effects The implementation uses balanced binary trees
191. commands ocamlc o fib fib ml fib 10 89 fib 20 10946 24 Chapter 2 Labels and variants Chapter written by Jacques Garrigue This chapter gives an overview of the new features in Objective Caml 3 labels and polymorphic variants 2 1 Labels If you have a look at the standard library you will see that function types have annotations you did not see in the functions you defined yourself List map f a gt b gt a list gt b list lt fun gt String sub string gt pos int gt len int gt string lt fun gt Such annotations of the form name are called labels They are meant to document the code and allow more checking where needed You can simply add them in interfaces just like they appear in the above types but you can also give names to arguments in your programs by prefixing them with a tilde let f x y x ys val f x int gt y int gt int lt fun gt let x 3 and y 2 in f x y int 1 When you want to use distinct names for the variable and the label appearing in the type you can use a naming label of the form name This also applies when the argument is not a variable let f x x1 y yl x1 yl val f x int gt y int gt int lt fun gt f x 3 y 2 int 1 Labels obey the same rules as other identifiers in Caml that is you cannot use a reserved keyword like in or to as label
192. compilation meaning that labeling rules are applied strictly and commutation between arguments is allowed See section 2 1 4 rectypes Allow arbitrary recursive types during type checking By default only recursive types where the recursion goes through an object type are supported w warning list Enable or disable warnings according to the argument warning list All options can also be modified inside the application by the Modules Path editor and Compiler Preferences commands They are inherited when you start a toplevel shell 171 172 14 2 Viewer This is the first window you get when you start OCamlBrowser It displays the list of modules in the load path Click on one to start your trip e The entry line at the bottom allows one to search for an identifier in all modules wildcards 2 and allowed If the input contains an arrow gt the search is done by type inclusion cf Search Symbol Included type e The Close all button is there to dismiss the windows created during you trip every click creates one By double clicking on it you will quit the browser e File Open and File Editor give access to the editor e File Shell creates an Objective Caml subprocess in a shell e Modules Path editor changes the load path Modules Reset cache rescans the load path and resets the module cache Do it if you recompile some interface or get confused about what is in the cache e Module
193. constr name as a constant constructor Constructor names must be capitalized The type representation field decl field decl describes a record type The field declarations field decl field decl describe the fields associated to this record type The field declaration field name typexpr declares field name as a field whose argument has type typexpr Chapter 6 The Objective Caml language 111 The field declaration mutable field name typexpr behaves similarly in addition it allows physical modification over the argument to this field The two components of a type definition the optional equation and the optional representation can be combined independently giving rise to four typical situations Abstract type no equation no representation When appearing in a module signature this definition specifies nothing on the type con structor besides its number of parameters its representation is hidden and it is assumed incompatible with any other type Type abbreviation an equation no representation This defines the type constructor as an abbreviation for the type expression on the right of the sign New variant type or record type no equation a representation This generates a new type constructor and defines associated constructors or fields through which values of that type can be directly built or inspected Re exported variant type or record type an equation a representation In this case the type constru
194. ctives and auxiliary functions required by the semantic actions of the rules The trailer goes at the end of the output file 12 4 2 Declarations Declarations are given one per line They all start with a sign token symbol symbol Declare the given symbols as tokens terminal symbols These symbols are added as constant constructors for the token concrete type token lt type gt symbol symbol Declare the given symbols as tokens with an attached attribute of the given type These symbols are added as constructors with arguments of the given type for the token concrete type The type part is an arbitrary Caml type expression except that all type constructor names must be fully qualified e g Modname typename for all types except standard built in types even if the proper open directives e g open Modname were given in the header section That s because the header is copied only to the m1 output file but not to the mli output file while the type part of a token declaration is copied to both start symbol symbol Declare the given symbols as entry points for the grammar For each entry point a parsing function with the same name is defined in the output module Non terminals that are not declared as entry points have no such parsing function Start symbols must be given a type with the type directive below itype lt type gt symbol symbol Specify the type of the semantic attributes for the given symbols This is
195. ctor is defined as an abbreviation for the type expression given in the equation but in addition the constructors or fields given in the representation remain attached to the defined type constructor The type expression in the equation part must agree with the representation it must be of the same kind record or variant and have exactly the same constructors or fields in the same order with the same arguments The construct constraint ident typexpr allows to specify type parameters Any actual type argument corresponding to the type parameter ident have to be an instance of typexpr more precisely ident and typexpr are unified Type variables of typexpr can appear in the type equation and the type declaration 6 8 2 Exception definitions exception definition exception constr decl exception cconstr name cconstr exception ncconstr name ncconstr Exception definitions add new constructors to the built in variant type exn of exception values The constructors are declared as for a definition of a variant type The form exception constr decl generates a new exception distinct from all other exceptions in the system The form exception name constr gives an alternate name to an existing exception 6 9 Classes Classes are defined using a small language similar to the module language 112 6 9 1 Class types Class types are the class level equivalent of type expressions they specify the general shape and type proper
196. ctory Too many open files by the process Too many links Filename too long Too many open files in the system No such device No such file or directory Not an executable file No locks available Not enough memory No space left on device Function not supported Not a directory Directory not empty Inappropriate I 0 control operation No such device or address Operation not permitted Broken pipe Result too large Read only file system Invalid seek e g on a pipe No such process Invalid link Additional errors mostly BSD EWOULDBLOCK EINPROGRESS EALREADY ENOTSOCK EDESTADDRREQ EMSGSIZE Cx Cx x Cx x x Operation would block Operation now in progress Operation already in progress Socket operation on non socket Destination address required Message too long Chapter 20 The unix library Unix system calls 297 EPROTOTYPE Protocol wrong type for socket ENOPROTOOPT Protocol not available EPROTONOSUPPORT Protocol not supported ESOCKTNOSUPPORT Socket type not supported EOPNOTSUPP Operation not supported on socket EPFNOSUPPORT Protocol family not supported EAFNOSUPPORT Address family not supported by protocol family EADDRINUSE Address already in use EADDRNOTAVAIL Can t assign requested address ENETDOWN Network is down ENETUNREACH Network
197. d expr typexpr expr expr expr neconstr expr tag name expr expr expr expr expr expr expr field expr field expr expr argument prefix symbol expr expr infix op expr expr field expr field lt expr expr expr expr expr lt expr expr expr expr expr lt expr if expr then expr else expr while expr do expr done for ident expr to downto expr do expr done expr expr match expr with pattern matching function pattern matching fun multiple matching try expr with pattern matching let rec let binding and let binding in expr new class path expr method name expr gt typexpr expr typexpr gt typexpr lt inst var name expr inst var name expr gt argument expr Jabel name Jabel name expr label name label name expr 100 pattern matching pattern when expr gt expr pattern when expr gt expr multiple matching parameter when expr gt expr let binding pattern typexpr expr value name parameter typexpr expr parameter pattern label name label name typexpr label name pattern label name label name typexpr expr label name pattern label name pattern typexpr expr infix op infix symbol or amp The table below shows the relative precedences and associativity of opera
198. d 346 split 273 328 split_delim 328 sprintf 255 281 sqrt 227 square_num 320 stable_sort 242 273 Stack module 286 Stack_overflow exception 223 stat 257 302 std_formatter 252 stdbuf 252 stderr 230 299 stdin 230 299 stdout 230 299 Str module 325 str_formatter 252 Stream module 287 string 245 String module 288 string_after 329 string_before 329 string_match 326 string_of_bool 229 string_of_float 229 string_of_inet_addr 310 string_of_int 229 string_of_num 322 string_partial_match 326 sub 241 262 265 277 289 sub_num 320 substitute_first 328 substring 245 succ 225 263 265 277 succ_num 321 symbol_end 279 384 symbol_start 279 symlink 305 sync 336 synchronize 346 Sys module 291 Sys_blocked_io exception 223 Sys_error exception 223 system 299 337 take 282 tan 227 tanh 228 tcdrain 316 tcflow 316 tcflush 316 tcgetattr 315 tcsendbreak 316 tcsetattr 315 temp_file 246 text_size 343 Thread module 332 ThreadUnix module 336 time 291 307 timed_read 337 timed_write 337 times 308 Tk module 352 t1 269 to_buffer 276 to_channel 275 to_float 264 266 279 to_int 264 266 278 to_int32 267 279 to_list 242 to_nativeint 267 to_string 264 267 276 279 280 top 286 total_size 276 transp 344 truncate 228 301 try_lock 334 umask 302 uncapitalize 290 Undefined exception 267 Unix module 295
199. d Main can refer to it but Aux cannot refer to Main Notice that only top level structures can be mapped to separately compiled files but not func tors nor module types However all module class objects can appear as components of a structure so the solution is to put the functor or module type inside a structure which can then be mapped to a file Chapter 5 Advanced examples with classes and modules Chapter written by Didier R my In this chapter we show some larger examples using objects classes and modules We review many of the object features simultaneously on the example of a bank account We show how modules taken from the standard library can be expressed as classes Lastly we describe a programming pattern know of as virtual types through the example of window managers 5 1 Extended example bank accounts In this section we illustrate most aspects of Object and inheritance by refining debugging and specializing the following initial naive definition of a simple bank account We reuse the module Euro defined at the end of chapter 3 let euro new Euro c val euro float gt Euro c lt fun gt let zero euro 0 val zero Euro c lt obj gt let neg x x times 1 val neg lt times float gt a gt gt a lt fun gt class account object val mutable balance zero method balance balance method deposit x balance lt balance plus x method wi
200. d compilation unit are evaluated No facilities are provided to access value names defined by the unit Therefore the unit must register itself its entry points with the main program e g by modifying tables of functions val loadfile_private string gt unit Same as loadfile except that the module loaded is not made available to other modules dynamically loaded afterwards val add_interfaces units string list gt paths string list gt unit add_interfaces units path grants dynamically linked object files access to the compilation units named in list units The interfaces cmi files for these units are searched in path a list of directory names Initially dynamically linked object files do not 349 390 have access to any of the compilation units composing the running program not even the standard library add_interfaces or add_available_units see below must be called to grant access to some of the units val add_available_units string Digest t list gt unit Same as add_interfaces but instead of searching cmi files to find the unit interfaces uses the interface digests given for each unit This way the cmi interface files need not be available at run time The digests can be extracted from cmi files using the extract_cre program installed in the Objective Caml standard library directory val clear_available_units unit gt unit Clear the list of compilation units accessible to dynamically linked progr
201. d binary mode this function behaves like open_out open_out_gen mode open_flag list gt perm int gt string gt out_channel Open the named file for writing as above The extra argument mode specify the opening mode The extra argument perm specifies the file permissions in case the file must be created open_out and open_out_bin are special cases of this function flush out_channel gt unit Flush the buffer associated with the given output channel performing all pending writes on that channel Interactive programs must be careful about flushing standard output and standard error at the right time output_char out_channel gt char gt unit Write the character on the given output channel output_string out_channel gt string gt unit Write the string on the given output channel Chapter 18 The core library 233 val val val val val val val val val output out_channel gt buf string gt pos int gt len int gt unit Write len characters from string buf starting at offset pos to the given output channel Raise Invalid_argument output if pos and len do not designate a valid substring of buf output_byte out_channel gt int gt unit Write one 8 bit integer as the single character with that code on the given output channel The given integer is taken modulo 256 output_binary_int out_channel gt int gt unit Write one integer in binary format on the given
202. d buff ofs len writes len characters to descriptor fd taking them from string buff starting at position ofs in string buff Return the number of characters actually written Interfacing with the standard input output library val in_channel_of_descr file_descr gt in_channel Create an input channel reading from the given descriptor The channel is initially in binary mode use set_binary_mode_in ic false if text mode is desired val out_channel_of_descr file_descr gt out_channel Create an output channel writing on the given descriptor The channel is initially in binary mode use set_binary_mode_out oc false if text mode is desired val descr_of_in_channel in_channel gt file_descr Return the descriptor corresponding to an input channel val descr_of_out_channel out_channel gt file_descr Return the descriptor corresponding to an output channel Chapter 20 The unix library Unix system calls 301 Seeking and truncating type seek_command SEEK_SET SEEK_CUR SEEK_END Positioning modes for lseek SEEK_SET indicates positions relative to the beginning of the file SEEK_CUR relative to the current position SEEK_END relative to the end of the file val lseek file_descr gt int gt mode seek_command gt int Set the current position for a file descriptor val truncate string gt len int gt unit Truncates the named file to the given size val ftruncate file_descr gt len int gt unit Trunc
203. d compilation information 17 1 1 Declaring primitives User primitives are declared in an implementation file or struct end module expression using the external keyword external name type C function name This defines the value name name as a function with type type that executes by calling the given C function For instance here is how the input primitive is declared in the standard library module Pervasives external input in_channel gt string gt int gt int gt int input Primitives with several arguments are always curried The C function does not necessarily have the same name as the ML function External functions thus defined can be specified in interface files or sig end signatures either as regular values val name type thus hiding their implementation as a C function or explicitly as manifest external functions external name type C function name The latter is slightly more efficient as it allows clients of the module to call directly the C function instead of going through the corresponding Caml function The arity number of arguments of a primitive is automatically determined from its Caml type in the external declaration by counting the number of function arrows in the type For instance input above has arity 4 and the input C function is called with four arguments Similarly 193 194 external input2 in_channel string int int gt int input2 has arity 1 and th
204. d first then the standard library directory Directories added with I are searched after the current directory in the order in which they were given on the command line but before the standard library directory inline n Set aggressiveness of inlining to n where n is a positive integer Specifying inline 0 prevents all functions from being inlined except those whose body is smaller than the call site Thus inlining causes no expansion in code size The default aggressiveness inline 1 allows slightly larger functions to be inlined resulting in a slight expansion in code size Higher values for the inline option cause larger and larger functions to become candidate for inlining but can result in a serious increase in code size labels Switch to the commuting label mode of compilation meaning that labeling rules are applied strictly and commutation between labeled arguments is allowed See section 2 1 4 This mode cannot be used to compile a program written in the default classic style but modules written in the two styles can be mixed in the same application linkall Forces all modules contained in libraries to be linked in If this flag is not given unreferenced modules are not linked in When building a library a flag setting the linkall flag forces all subsequent links of programs involving that library to link all the modules contained in the library noassert Turn assertion checking off assertions are not compiled
205. d in module type are implemented in module expr and their implementation meets the requirements given in module type In other terms it checks that the implementation module expr meets the type specification module type The whole expression evaluates to the same module as module expr except that all components not specified in module type are hidden and can no longer be accessed 6 11 2 Structures Structures struct end are collections of definitions for value names type names exceptions module names and module type names The definitions are evaluated in the order in which they appear in the structure The scope of the bindings performed by the definitions extend to the end of the structure As a consequence a definition may refer to names bound by earlier definitions in the same structure For compatibility with toplevel phrases chapter 9 and with Caml Light an optional is allowed after each definition in a structure The has no semantic meaning Also for compatibility expr is allowed as a component of a structure meaning let _ expr i e evaluate expr for its side effects Value definitions A value definition let rec let binding and let binding bind value names in the same way as a let in expression see section 6 7 1 The value names appearing in the left hand sides of the bindings are bound to the corresponding values in the right hand sides Chapter 6 The Objective Caml language 123 A value definition
206. d in the curses library The stub code file curses o looks like 208 include lt curses h gt include lt mlvalues h gt value curses_initscr value unit return value initscr OK to coerce directly from WINDOW to value since that s a block created by malloc value curses_wrefresh value win wrefresh WINDOW win return Val_unit value curses_newwin value nlines value ncols value x0 value y0 return value newwin Int_val nlines Int_val ncols Int_val x0 Int_val y0 value curses_addch value c addch Int_val c Characters are encoded like integers return Val_unit value curses_addstr value s addstr String_val s return Val_unit This goes on for pages The file curses c can be compiled with cc c I usr local lib ocaml curses c or even simpler ocamlc c curses c When passed a c file the ocamlc command simply calls the C compiler on that file with the right I option Now here is a sample Caml program test ml that uses the curses module Chapter 17 Interfacing C with Objective Caml 209 open Curses let main_window initscr in let small_window newwin 10 5 20 10 in mvwaddstr main_window 10 2 Hello mvwaddstr small_window 4 3 world refresh for i 1 to 100000 do done endwin To compile this program run ocamlc c test ml Finally to link everything together ocamlc custom o test test cmo curses o cc
207. d is composed of two units mod4 and modd The list of object files for prog2 PROG2_OBJS mod4 cmx mod5 cmx prog2 PROG2_OBJS OCAMLOPT o prog2 OCAMLFLAGS PROG2_O0BJS Common rules OUFFIXES ml mli cmo cmi cmx ml cmo OCAMLC OCAMLFLAGS c lt mli cmi OCAMLC OCAMLFLAGS c lt ml cmx OCAMLOPT OCAMLOPTFLAGS c lt Clean up clean rm f progi prog2 rm f cm iox Chapter 13 Dependency generator ocamldep 169 Dependencies depend OCAMLDEP INCLUDES mli ml gt depend include depend 170 Chapter 14 The browser editor ocamlbrowser This chapter describes OCamlBrowser a source and compiled interface browser written using LablTk This is a useful companion to the programmer Its functions are e navigation through Objective Caml s modules using compiled interfaces e source editing type checking and browsing e integrated Objective Caml shell running as a subprocess 14 1 Invocation The browser is started by the command ocamlrowser as follows ocamlbrowser options The following command line options are recognized by ocamlbrowser I directory Add the given directory to the list of directories searched for source and compiled files By default only the standard library directory is searched The standard library can also be changed by setting the CAMLLIB environment variable labels Switch to the commuting label mode of
208. difier Control Shift Lock Buttoni Button2 Button3 Button4 Buttond Double Triple Mod1 Mod2 Mod3 Mod4 Mod5 Meta Alt type event ButtonPress ButtonPressDetail int ButtonRelease ButtonReleaseDetail int Circulate ColorMap Configure Destroy Enter Expose FocusIn FocusOut Gravity KeyPress KeyPressDetail string KeyRelease KeyReleaseDetail string Leave Map Motion Property Reparent Unmap Visibility Modified modifier list event An event can be either a basic X event or modified by a key or mouse modifier type eventInfo mutable ev_Above int mutable ev_ButtonNumber int mutable ev_Count int mutable ev_Detail string mutable ev_Focus bool mutable ev_Height int mutable ev_KeyCode int mutable ev_Mode string Chapter 27 The LabITk library Tcl Tk GUI interface 355 mutable ev_OverrideRedirect bool mutable ev_Place string mutable ev_State string mutable ev_Time int mutable ev_Width int mutable ev_MouseX int mutable ev_MouseY int mutable ev_Char string mutable ev_BorderWidth int mutable ev_SendEvent bool mutable ev_KeySymString string mutable ev_KeySymInt int mutable ev_RootWindow int mutable ev_SubWindow int mutable ev_Type int mutable ev_Widget Widget any Widget widget mutable ev_
209. ds The expression expr exprs lt expr modifies in place the array denoted by expr replac ing element number expr by the value of expr The exception Invalid_argument is raised if the access is out of bounds The value of the whole expression is Strings The expression expr exprs returns the value of character number exprs in the string denoted by expr The first character has number 0 the last character has number n 1 where n is the length of the string The exception Invalid_argument is raised if the access is out of bounds Chapter 6 The Objective Caml language 107 The expression expr expry lt exprs modifies in place the string denoted by expry replacing character number expr by the value of expr The exception Invalid_argument is raised if the access is out of bounds The value of the whole expression is 6 7 4 Operators Symbols from the class infix symbol1s as well as the keywords or and amp can appear in infix position between two expressions Symbols from the class prefix symbols can appear in prefix position in front of an expression Infix and prefix symbols do not have a fixed meaning they are simply interpreted as applications of functions bound to the names corresponding to the symbols The expression prefix symbol expr is interpreted as the application prefix symbol expr Similarly the expression expr infix symbol expr is interpreted as the application infix symbo
210. ds int heap_chunks int live_words int live_blocks int free_words int free_blocks int largest_free int fragments int compactions int 256 The memory management counters are returned in a stat record The fields of this record are minor_words Number of words allocated in the minor heap since the program was started promoted_words Number of words allocated in the minor heap that survived a minor collection and were moved to the major heap since the program was started major_words Number of words allocated in the major heap including the promoted words since the program was started minor_collections Number of minor collections since the program was started major_collections Number of major collection cycles not counting the current cycle since the program was started heap_words Total size of the major heap in words heap_chunks Number of times the major heap size was increased since the program was started including the initial allocation of the heap live_words Number of words of live data in the major heap including the header words live_blocks Number of live blocks in the major heap free_words Number of words in the free list free_blocks Number of blocks in the free list largest_free Size in words of the largest block in the free list fragments Number of wasted words due to fragmentation These are 1 words free blocks placed between two live blocks They cannot be inserted in th
211. ds whose fields all have static type float are represented as arrays of floating point numbers with tag Double_array_tag See the section below on arrays 17 3 3 Arrays Arrays of integers and pointers are represented like tuples that is as pointers to blocks tagged 0 They are accessed with the Field macro for reading and the modify function for writing Arrays of floating point numbers type float array have a special unboxed more efficient representation These arrays are represented by pointers to blocks with tag Double_array_tag They should be accessed with the Double_field and Store_double_field macros 17 3 4 Concrete types Constructed terms are represented either by unboxed integers for constant constructors or by blocks whose tag encode the constructor for non constant constructors The constant constructors and the non constant constructors for a given concrete type are numbered separately starting from 0 in the order in which they appear in the concrete type declaration Constant constructors 200 are represented by unboxed integers equal to the constructor number Non constant constructors declared with a n tuple as argument are represented by a block of size n tagged with the constructor number the n fields contain the components of its tuple argument Other non constant constructors are represented by a block of size 1 tagged with the constructor number the field 0 contains the value of the constructor argument Ex
212. e Nw S Sel Sw W type fillMode Both None X Y type side Bottom Left Right Top val pack fafter a Widget widget gt anchor anchor gt before b Widget widget gt expand bool gt fill fillMode gt inside c Widget widget gt ipadx int gt ipady int gt padx int gt pady int gt side side gt d Widget widget list gt unit Pack a widget inside its parent using the standard layout engine val grid column int gt columnspan int gt inside a Widget widget gt ipadx int gt ipady int gt padx int gt pady int gt row int gt rowspan int gt sticky string gt b Widget widget list gt unit Pack a widget inside its parent using the grid layout engine type borderMode Ignore Inside Outside val place fanchor anchor gt bordermode borderMode gt 304 height int gt inside a Widget widget gt relheight float gt relwidth float gt relx float gt rely float gt width int gt x int gt y int gt b Widget widget gt unit Pack a widget inside its parent at absolute coordinates val raise_window above a Widget widget gt b Widget widget gt unit val lower_window below a Widget widget gt b Widget widget gt unit Raise or lower the window associated to a widget Event handling type mo
213. e a b kind captures this association of a Caml type a for values read or written in the big array and of an element kind b which represents the actual contents of the big array The following predefined values of type kind list all possible associations of Caml types with element kinds float32 float float32_elt kind float64 float float64_elt kind int8_signed int int8_signed_elt kind int8_unsigned int int8_unsigned_elt kind int16_signed int inti6_signed_elt kind inti6_unsigned int int16_unsigned_elt kind int int int_elt kind int32 int32 int32_elt kind int64 int64 int64_elt kind nativeint nativeint nativeint_elt kind char char int8_unsigned_elt kind As shown by the types of the values above big arrays of kind float32_elt and float64_elt are accessed using the Caml type float Big arrays of integer kinds are accessed using the smallest Caml integer type large enough to represent the array elements int for 8 and 16 bit integer bigarrays as well as Caml integer bigarrays int32 for 32 bit integer bigarrays int64 for 64 bit integer bigarrays and nativeint for platform native integer bigarrays Finally big arrays of kind int8_unsigned_elt can also be accessed as arrays of characters instead of arrays of small integers by using the kind value char instead of int8_unsigned Array layouts type c_layout type fortran_layout To facilitate interoperability with existing C and Fortra
214. e Negative let sign_int n if n gt 0 then Positive else Negative val sign_int int gt sign lt fun gt To define arithmetic operations for the number type we use pattern matching on the two num bers involved let add_num ni n2 match ni n2 with Int i1 Int i2 gt Check for overflow of integer addition if sign_int i1 sign_int i2 amp amp sign_int il i2 lt gt sign_int il then Float float i1 float i2 else Int i1 i2 Int i1 Float f2 gt Float float i1 f2 Float f1 Int i2 gt Float f1 float i2 Float f1 Float f2 gt Float f1 f2 Error _ gt Error _ Error gt Error val add_num number gt number gt number lt fun gt add_num Int 123 Float 3 14159 number Float 126 141590 The most common usage of variant types is to describe recursive data structures Consider for example the type of binary trees type a btree Empty Node of a a btree a btree type a btree Empty Node of a a btree a btree This definition reads as follow a binary tree containing values of type a an arbitrary type is either empty or is a node containing one value of type a and two subtrees containing also values of type a that is two a btree Operations on binary trees are naturally expressed as recursive functions following the same structure as the type definition
215. e The output of command is redirected to an intermediate file which is compiled If there are no compilation errors the intermediate file is deleted afterwards The name of this file is built from the basename of the source file with the extension ppi for an interface m1i file and ppo for an implementation m1 file rectypes Allow arbitrary recursive types during type checking By default only recursive types where the recursion goes through an object type are supported thread Compile or link multithreaded programs in combination with the threads library described in chapter 23 What this option actually does is select a special thread safe version of the standard library unsafe Turn bound checking off on array and string accesses the v i and s i constructs Chapter 8 Batch compilation ocamlc 135 Programs compiled with unsafe are therefore slightly faster but unsafe anything can happen if the program accesses an array or string outside of its bounds use runtime runtime name Generate a bytecode executable file that can be executed on the custom runtime system runtime name built earlier with ocamlc make runtime runtime name See section 17 1 4 for more information v Print the version number of the compiler w warning list Enable or disable warnings according to the argument warning list The argument is a string of one or several characters with the following meaning for each character A a enable
216. e queued val key_pressed unit gt bool Return true if a keypress is available that is if read_key would not block 346 Sound val sound freq int gt ms int gt unit sound freq dur plays a sound at frequency freq in hertz for a duration dur in milliseconds Double buffering val auto_synchronize bool gt unit By default drawing takes place both on the window displayed on screen and in a memory area the backing store The backing store image is used to re paint the on screen window when necessary To avoid flicker during animations it is possible to turn off on screen drawing perform a number of drawing operations in the backing store only then refresh the on screen window explicitly auto_synchronize false turns on screen drawing off All subsequent drawing commands are performed on the backing store only auto_synchronize true refreshes the on screen window from the backing store as per synchronize then turns on screen drawing back on All subsequent drawing commands are performed both on screen and in the backing store The default drawing mode corresponds to auto_synchronize true val synchronize unit gt unit Synchronize the backing store and the on screen window by copying the contents of the backing store onto the graphics window val display_mode bool gt unit Set display mode on or off When turned on drawings are done in the graphics window when turned off drawing
217. e Num operation on arbitrary precision numbers Module Arith_status flags that control rational arithmetic 22 The str library regular expressions and string processing 22 1 Module Str regular expressions and high level string processing 23 The threads library 23 1 23 2 23 3 23 4 23 5 Module Thread lightweight threads 2 2 2 ee Module Mutex locks for mutual exclusion 0 0 0 00000002 ee Module Condition condition variables to synchronize between threads Module Event first class synchronous communication Module ThreadUnix thread compatible system calls 24 The graphics library 24 1 Module Graphics machine independent graphics primitives 25 The dbm library access to NDBM databases 25 1 Module Dbm interface to the NDBM database 0004 26 The dynlink library dynamic loading and linking of object files 26 1 Module Dynlink dynamic loading of bytecode object files 27 The LablTk library Tcl Tk GUI interface 27 1 Module Tk basic functions and types for LablTk 295 295 319 319 322 325 325 331 332 334 334 335 336 339 340 347 347 349 349 351 28 The bigarray library 357 28 1 Module Bigarray large multi dimensional numerical arrays 358 28 2 Big arrays in the Caml C interface 2 0 2 0
218. e formatter ff The format is a character string which contains three types of objects plain characters and conversion specifications as specified in the printf module and pretty printing indications The pretty printing indication characters are introduced by a character and their meanings are open a pretty printing box The type and offset of the box may be optionally specified with the following syntax the lt character followed by an optional box type indication then an optional integer offset and the closing gt character Box type is one of h v hv b or hov which stand respectively for an horizontal box a vertical box an horizontal vertical box or an horizontal or vertical box b standing for an horizontal or vertical box demonstrating indentation and hov standing for a regular horizontal or vertical box For instance lt hov 2 gt opens an horizontal or vertical box with indentation 2 as obtained with open_hovbox 2 For more details about boxes see the various box opening functions open_ box close the most recently opened pretty printing box output a good break as with print_cut output a space as with print_space n force a newline as with force_newline output a good break as with print_break The nspaces and offset parameters of the break may be optionally specified with the following syntax the lt character followed by an integer nspaces value t
219. e free list thus they are not available for allocation compactions Number of heap compactions since the program was started The total amount of memory allocated by the program since it was started is in words minor_words major_words promoted_words Multiply by the word size 4 on a 32 bit machine 8 on a 64 bit machine to get the number of bytes type control mutable minor_heap_size int mutable major_heap_increment int mutable space_overhead int mutable verbose int mutable max_overhead int mutable stack_limit int The GC parameters are given as a control record The fields are minor_heap_size The size in words of the minor heap Changing this parameter will trigger a minor collection Default 32k major_heap_increment The minimum number of words to add to the major heap when increasing it Default 62k space_overhead The major GC speed is computed from this parameter This is the memory that will be wasted because the GC does not immediatly collect unreachable Chapter 19 The standard library 257 val val val val val val blocks It is expressed as a percentage of the memory used for live data The GC will work more use more CPU time and collect blocks more eagerly if space_overhead is smaller The computation of the GC speed assumes that the amount of live data is constant Default 42 max_overhead Heap compaction is triggered when the estimated amount of free memory is mo
220. e heap size this is probably an attempt to build an excessively large array or string 150 Chapter 11 Native code compilation ocamlopt This chapter describes the Objective Caml high performance native code compiler ocamlopt which compiles Caml source files to native code object files and link these object files to produce standalone executables The native code compiler is only available on certain platforms It produces code that runs faster than the bytecode produced by ocamlc at the cost of increased compilation time and executable code size Compatibility with the bytecode compiler is extremely high the same source code should run identically when compiled with ocamlc and ocamlopt It is not possible to mix native code object files produced by ocamlc with bytecode object files produced by ocamlopt a program must be compiled entirely with ocamlopt or entirely with ocamlc Native code object files produced by ocamlopt cannot be loaded in the toplevel system ocaml 11 1 Overview of the compiler The ocamlopt command has a command line interface very close to that of ocamlc It accepts the same types of arguments e Arguments ending in mli are taken to be source files for compilation unit interfaces In terfaces specify the names exported by compilation units they declare value names with their types define public data types declare abstract data types and so on From the file xz mli the ocamlopt compiler produces a compiled
221. e input2 C function receives one argument which is a quadruple of Caml values Type abbreviations are not expanded when determining the arity of a primitive For instance type int_endo int gt int external f int_endo gt int_endo f external g int gt int gt int gt int f f has arity 1 but g has arity 2 This allows a primitive to return a functional value as in the f example above just remember to name the functional return type in a type abbreviation 17 1 2 Implementing primitives User primitives with arity n lt 5 are implemented by C functions that take n arguments of type value and return a result of type value The type value is the type of the representations for Caml values It encodes objects of several base types integers floating point numbers strings as well as Caml data structures The type value and the associated conversion functions and macros are described in details below For instance here is the declaration for the C function implementing the input primitive value input value channel value buffer value offset value length When the primitive function is applied in a Caml program the C function is called with the values of the expressions to which the primitive is applied as arguments The value returned by the function is passed back to the Caml program as the result of the function application User primitives with arity greater than 5 should be implemented by t
222. e ocamlyacc command recognizes the following options v Generate a description of the parsing tables and a report on conflicts resulting from ambigu ities in the grammar The description is put in file grammar output Chapter 12 Lexer and parser generators ocamllex ocamlyacc 163 bprefix Name the output files prefiz ml prefix mli prefix output instead of the default naming convention 12 6 A complete example The all time favorite a desk calculator This program reads arithmetic expressions on standard input one per line and prints their values Here is the grammar definition File parser mly token lt int gt INT token PLUS MINUS TIMES DIV token LPAREN RPAREN token EOL left PLUS MINUS lowest precedence left TIMES DIV medium precedence Z nonassoc UMINUS highest precedence start main the entry point type lt int gt main Ah main expr EOL 1 expr INT 1 LPAREN expr RPAREN 2 expr PLUS expr 1 3 expr MINUS expr 1 3 expr TIMES expr 1 3 expr DIV expr 1 3 MINUS expr prec UMINUS 2 Here is the definition for the corresponding lexer File lexer ml1l open Parser The type token is defined in parser mli exception Eof rule token parse DNE token lexbuf skip blanks l P p EOL 0 9 INT int_of_string Lexing lexeme lexbuf o PLUS i MINUS 164 2
223. ect belonging to a subclass see section 6 4 Chapter 6 The Objective Caml language 117 Virtual class A class must be flagged virtual if one of its methods is virtual that is appears in the class type but is not actually defined Objects cannot be created from a virtual class Type parameters The class type parameters correspond to the ones of the class type and of the two type abbreviations defined by the class binding They must be bound to actual types in the class definition using type constraints So that the abbreviations are well formed type variables of the inferred type of the class must either be type parameters or be bound in the constraint clause 6 9 4 Class specification class specification class class spec and class spec class spec virtual type parameters class name class type This is the counterpart in signatures of class definitions A class specification matches a class definition if they have the same type parameters and their types match 6 9 5 Class type definitions classtype definition class type classtype def and classtype def classtype def virtual type parameters class name class body type A class type definition class class name class body type defines an abbreviation class name for the class body type class body type As for class definitions two type abbreviations class name and class name are also defined The definition can be parameterized by some type
224. ed because no allocation takes place after it gets its value but it s easier and safer to simply register all the local variables that have type value Here is the same function written using the low level allocation functions We notice that the cons cells are small blocks and can be allocated with alloc_sma11 and filled by direct assignments on their fields value alloc_list_int int i1 int i2 CAMLparam0 CAMLlocal2 result r r alloc_small 2 0 Allocate a cons cell Field r 0 Val_int i2 car the integer i2 Field r 1 Val_int 0 cdr the empty list result alloc_small 2 0 Allocate the other cons cell Field result 0 Val_int ii car the integer il Field result 1 r cdr the first cons cell CAMLreturn result Chapter 17 Interfacing C with Objective Caml 207 In the two examples above the list is built bottom up Here is an alternate way that proceeds top down It is less efficient but illustrates the use of modify value alloc_list_int int i1 int i2 CAMLparam0 CAMLlocal2 tail r r alloc_small 2 0 Allocate a cons cell Field r 0 Val_int il car the integer il Field r 1 Val_int 0 A dummy value tail alloc_small 2 0 Allocate the other cons cell Field tail 0 Val_int i2 car the integer i2 Field tail 1 Val_int 0 cdr the empty list modify amp Field r 1 tail cdr o
225. eint processor native integers val val val val val val val val val val val val This module provides operations on the type nativeint of signed 32 bit integers on 32 bit platforms or signed 64 bit integers on 64 bit platforms This integer type has exactly the same width as that of a long integer type in the C compiler All arithmetic operations over nativeint are taken modulo 2 or 264 depending on the word size of the architecture zero nativeint one nativeint minus_one nativeint The native integers 0 1 1 neg nativeint gt nativeint Unary negation add nativeint gt nativeint gt nativeint Addition sub nativeint gt nativeint gt nativeint Subtraction mul nativeint gt nativeint gt nativeint Multiplication div nativeint gt nativeint gt nativeint Integer division Raise Division_by_zero if the second argument is zero rem nativeint gt nativeint gt nativeint Integer remainder If x gt 0 and y gt O the result of Nativeint rem x y satisfies the following properties 0 lt Nativeint rem x y lt y and x Nativeint add Nativeint mul Nativeint div x y y Nativeint rem x y Ify 0 Nativeint rem x y raises Division_by_zero If x lt Oor y lt 0 the result of Nativeint rem x y is not specified and depends on the platform succ nativeint gt nativeint Successor Nativeint succ xis Nativeint add x in pred nativeint gt
226. elect 305 333 336 337 self 332 self_init 283 send 312 335 338 sendto 312 338 set 240 257 289 293 Set module 283 set_all_formatter_output_functions 251 set_approx_printing 323 set_binary_mode_in 235 set_binary_mode_out 233 set_close_on_exec 303 set_color 341 set_ellipsis_text 251 set_error_when_null_denominator 322 set_floating_precision 323 set_font 343 set_formatter_out_channel 251 set_formatter_output_functions 251 set_line_width 343 set_margin 249 INDEX TO THE LIBRARY set_max_boxes 249 set_max_indent 249 set_nonblock 303 set_normalize_ratio 322 set_normalize_ratio_when_printing 323 set_signal 292 set_tab 250 set_text_size 343 setgid 309 setitimer 308 setsid 316 setsockopt 312 setuid 309 shift_left 263 266 278 shift_right 263 266 278 shift_right_logical 263 266 278 shutdown 311 shutdown_connection 313 sigabrt 292 sigalrm 292 sigchld 292 sigcont 292 sigfpe 292 sighup 292 sigill 292 sigint 292 sigkill 292 sign_num 321 signal 292 335 sigpending 306 sigpipe 292 sigprocmask 306 sigprof 292 sigquit 292 sigsegv 292 sigstop 292 sigsuspend 306 sigterm 292 sigtstp 292 sigttin 292 sigttou 292 sigusri 292 sigusr2 292 sigvtalrm 292 sin 227 383 sinh 228 size_x 341 size_y 341 sleep 308 337 snd 230 socket 311 338 socketpair 311 338 sort 242 273 Sort module 286 soun
227. ementation uses Merge Sort and is the same as List stable_sort val stable_sort cmp a gt a gt int gt a list gt a list Same as List sort but the sorting algorithm is stable The current implementation is Merge Sort It runs in constant heap space 19 17 Module Map association tables over ordered types This module implements applicative association tables also known as finite maps or dictionaries given a total ordering function over the keys All operations over maps are purely applicative no side effects The implementation uses balanced binary trees and therefore searching and insertion take time logarithmic in the size of the map module type OrderedType sig type t val compare t gt t gt int end The input signature of the functor Map Make t is the type of the map keys compare is a total ordering function over the keys This is a two argument function f such that f e1 e2 is zero if the keys e1 and e2 are equal f e1 e2 is strictly negative if e1 is smaller than e2 and f e1 e2 is strictly positive if e1 is greater than e2 Example a suitable ordering function is the generic structural comparison function compare 274 module type S sig type key The type of the map keys type a t The type of maps from type key to type a val empty at The empty map val add key key gt data a gt at gt at add x y m returns a map containing the same bindings as m plus a bindi
228. emporarily no data available raises the EAGAIN or EWOULDBLOCK error instead of blocking writing on a descriptor on which there is temporarily no room for writing also raises EAGAIN or EWOULDBLOCK val set_close_on_exec file_descr gt unit val clear_close_on_exec file_descr gt unit Set or clear the close on exec flag on the given descriptor A descriptor with the close on exec flag is automatically closed when the current process starts another program with one of the exec functions Directories val mkdir string gt perm file_perm gt unit Create a directory with the given permissions val rmdir string gt unit Remove an empty directory val chdir string gt unit Change the process working directory val getcwd unit gt string Return the name of the current working directory val chroot string gt unit Change the process root directory type dir_handle The type of descriptors over opened directories 304 val opendir string gt dir_handle Open a descriptor on a directory val readdir dir_handle gt string Return the next entry in a directory Raise End_of_file when the end of the directory has been reached val rewinddir dir_handle gt unit Reposition the descriptor to the beginning of the directory val closedir dir_handle gt unit Close a directory descriptor Pipes and redirections val pipe unit gt file_descr file_descr Create a pipe The first component of the r
229. end As in the case of simple structures an alternate syntax is provided for defining functors and restricting their result module AbstractSet Elt ORDERED_TYPE SET with type element Elt t struct end Abstracting a type component in a functor result is a powerful technique that provides a high degree of type safety as we now illustrate Consider an ordering over character strings that is different from the standard ordering implemented in the OrderedString structure For instance we compare strings without distinguishing upper and lower case module NoCaseString struct type t string let cmp si s2 OrderedString cmp String lowercase s1 String lowercase s2 end module NoCaseString sig type t string val cmp string gt string gt comparison end module NoCaseStringSet AbstractSet NoCaseString module NoCaseStringSet sig type element NoCaseString t and set AbstractSet NoCaseString set val empty set val add element gt set gt set val member element gt set gt bool end NoCaseStringSet add FOO AbstractStringSet empty This expression has type AbstractStringSet set AbstractSet OrderedString set but is here used with type NoCaseStringSet set AbstractSet NoCaseString set Notice that the two types AbstractStringSet set and NoCaseStringSet set are not compatible and values of these two types do not match This is the correct behavior even tho
230. engths val fold_right2 f Ca gt b gt c gt c gt a list gt b list gt init c gt c List fold_right2 f al an b1 bn cis f al b1 f a2 b2 f an bn c Raise Invalid_argument if the two lists have different lengths Not tail recursive List scanning val for_all f a gt bool gt a list gt bool for_all p at an checks if all elements of the list satisfy the predicate p That is it returns p a1 amp amp p a2 amp amp amp amp p an val exists f a gt bool gt a list gt bool exists p a1 an checks if at least one element of the list satisfies the predicate p That is it returns p al p a2 II Il p an val for_all2 f a gt b gt bool gt a list gt b list gt bool val exists2 f a gt b gt bool gt a list gt b list gt bool Same as for_all and exists but for a two argument predicate Raise Invalid_argument if the two lists have different lengths val mem a gt a list gt bool mem a 1 is true if and only if a is equal to an element of 1 val memg a gt a list gt bool Same as mem but uses physical equality instead of structural equality to compare list elements 272 List searching val find f a gt bool gt a list gt a find p 1 returns the first element of the list 1 that satisfies the predicate p Raise No
231. ent Chapter 3 Objects in Caml 55 3 14 Binary methods A binary method is a method which takes an argument of the same type as self The class comparable below is a template for classes with a binary method leq of type a gt bool where the type variable a is bound to the type of self Therefore comparable expands to lt leq a gt bool gt as a We see here that the binder as also allows to write recursive types class virtual comparable object _ a method virtual leq a gt bool end class virtual comparable object a method virtual leq a gt bool end We then define a subclass money of comparable The class money simply wraps floats as comparable objects We will extend it below with more operations There is a type constraint on the class parameter x as the primitive lt is a polymorphic comparison function in Objective Caml The inherit clause ensures that the type of objects of this class is an instance of comparable class money x float object inherit comparable val repr x method value repr method leq p repr lt p value end class money float gt object a val repr float method leq a gt bool method value float end Note that the type money1 is not a subtype of type comparable as the self type appears in contravariant position in the type of method leq Indeed an object m of class money has a method le
232. eption integer division by zero modulus by zero 156 stack overflow on the Alpha processor only floating point operations involving infinite or denormalized numbers all other processors supported by ocamlopt treat these numbers correctly as per the IEEE 754 standard In particular notice that stack overflow caused by excessively deep recursion is reported by most Unix kernels as a segmentation violation signal e Signals are detected only when the program performs an allocation in the heap That is if a signal is delivered while in a piece of code that does not allocate its handler will not be called until the next heap allocation The best way to avoid running into those incompatibilities is to never trap the Division_by_zero and Stack_overflow exceptions thus also treating them as fatal er rors with the bytecode compiler as well as with the native code compiler Test the divisor before performing the operation instead of trapping the exception afterwards Chapter 12 Lexer and parser generators ocamllex ocamlyacc This chapter describes two program generators ocamllex that produces a lexical analyzer from a set of regular expressions with associated semantic actions and ocamlyacc that produces a parser from a grammar with associated semantic actions These program generators are very close to the well known lex and yacc commands that can be found in most C programming environments This chapter a
233. er This module implements a simple standard lexical analyzer presented as a function from character streams to token streams It implements roughly the lexical conventions of Caml but is parameterized by the set of keywords of your language type token val Kwd of string Ident of string Int of int Float of float String of string Char of char The type of tokens The lexical classes are Int and Float for integer and floating point numbers String for string literals enclosed in double quotes Char for character literals enclosed in single quotes Ident for identifiers either sequences of letters digits underscores and quotes or sequences of operator characters such as etc and Kwd for keywords either identifiers or single special characters such as etc make_lexer string list gt char Stream t gt token Stream t Construct the lexer function The first argument is the list of keywords An identifier s is returned as Kwd s if s belongs to this list and as Ident s otherwise A special character s is returned as Kwd s if s belongs to this list and cause a lexical error exception Parse_error otherwise Blanks and newlines are skipped Comments delimited by and are skipped as well and can be nested Example a lexer suitable for a desk calculator is obtained by let lexer make_lexer wou Wy UPAL gt let won The associated parser would be a function
234. erator precedence and print parentheses around an operator only if its precedence is less than the current precedence let print_expr exp Local function definitions let open_paren prec op_prec if prec gt op_prec then print_string in let close_paren prec op_prec if prec gt op_prec then print_string in let rec print prec exp prec is the current precedence match exp with Const c gt print_float c Var v gt print_string v Sum f g gt open_paren prec 0 print 0 f print_string print 0 g close_paren prec 0 Diff f g gt open_paren prec 0 print 0 f print_string print 1 g close_paren prec 0 Prod f g gt open_paren prec 2 Chapter 1 The core language 21 print 2 f print_string print 2 g close_paren prec 2 Quot f g gt open_paren prec 2 print 2 f print_string print 3 g close_paren prec 2 in print O exp val print_expr expression gt unit lt fun gt let e Sum Prod Const 2 0 Var x Const 1 0 val e expression Sum Prod Const 2 000000 Var x Const 1 000000 print_expr e print_newline 2 x t i1 unit print_expr deriv e x print_newline N x1 0 x x 0 unit Parsing transforming concrete syntax into abstract syntax is usually more delicate Caml offers several tools to help write parsers on the one hand
235. erence to false String of string gt unit Call the function with a string argument Int of int gt unit Call the function with an int argument val Rest of string gt unit Stop interpreting keywords and call the function with each remaining argument The concrete type describing the behavior associated with a keyword parse keywords string spec string list gt others string gt unit gt errmsg string gt unit Arg parse speclist anonfun usage_msg parses the command line speclist is a list of triples key spec doc key is the option keyword it must start with a character spec gives the option type and the function to call when this option is found on the command line doc is a one line description of this option anonfun is called on anonymous arguments The functions in spec and anonfun are called in the same order as their arguments appear on the command line If an error occurs Arg parse exits the program after printing an error message as follows The reason for the error unknown option invalid or missing argument etc usage_msg The list of options each followed by the corresponding doc string 240 For the user to be able to specify anonymous arguments starting with a include for example String anonfun doc in speclist By default parse recognizes a unit option help which will display usage_msg and the list of options and exit the program Y
236. esenting the character Raise End_of_file if an end of file was reached input_binary_int in_channel gt int Read an integer encoded in binary format from the given input channel See output_binary_int Raise End_of_file if an end of file was reached while reading the integer input_value in_channel gt a Read the representation of a structured value as produced by output_value and return the corresponding value This function is identical to Marshal from_channel see the description of module Marshal for more information in particular concerning the lack of type safety seek_in in_channel gt int gt unit seek_in chan pos sets the current reading position to pos for channel chan This works only for regular files On files of other kinds the behavior is unspecified pos_in in_channel gt int Return the current reading position for the given channel in_channel_length in_channel gt int Return the total length number of characters of the given channel This works only for regular files On files of other kinds the result is meaningless close_in in_channel gt unit Close the given channel Anything can happen if any of the functions above is called on a closed channel set_binary_mode_in in_channel gt bool gt unit set_binary_mode_in ic true sets the channel ic to binary mode no translations take place during input set_binary_mode_out ic false sets the channel ic to text mode depend
237. esult is opened for reading that s the exit to the pipe The second component is opened for writing that s the entrance to the pipe val mkfifo string gt perm file_perm gt unit Create a named pipe with the given permissions High level process and redirection management val create_process prog string gt args string array gt stdin file_descr gt stdout file_descr gt stderr file_descr gt int create_process prog args new_stdin new_stdout new_stderr forks a new process that executes the program in file prog with arguments args The pid of the new process is returned immediately the new process executes concurrently with the current process The standard input and outputs of the new process are connected to the descriptors new_stdin new_stdout and new_stderr Passing e g stdout for new_stdout prevents the redirection and causes the new process to have the same standard output as the current process The executable file prog is searched in the path The new process has the same environment as the current process All file descriptors of the current process are closed in the new process except those redirected to standard input and outputs val create_process_env prog string gt args string array gt env string array gt stdin file_descr gt stdout file_descr gt stderr file_descr gt int create_process_env prog args env new_stdin new_stdout new_stderr works as create_process except that the extra arg
238. expr option gt typexpry Tuple types The type expression typexpr typexpr denotes the type of tuples whose elements belong to types typexpr typexpr respectively Constructed types Type constructors with no parameter as in typeconstr are type expressions The type expression typexpr typeconstr where typeconstr is a type constructor with one pa rameter denotes the application of the unary type constructor typeconstr to the type typexpr The type expression typexpr typexpr typeconstr where typeconstr is a type construc tor with n parameters denotes the application of the n ary type constructor typeconstr to the types typexpr through typexpr Recursive types The type expression typexpr as ident denotes the same type as typexpr and also binds the type variable ident to type typexpr both in typexpr and in the remaining part of the type If the type variable ident actually occurs in typexpr a recursive type is created Recursive types for which there exists a recursive path that does not contain an object type constructor are rejected Variant types tag spec tag spec gt tag spec tag spec variant type Std lt tag spec full tag spec full gt tag name tag spec tag name typexpr tag spec full tag name typexpr amp typexpr Variant types describe the values a polymorphic variant may take The first case is an exact variant type all possible t
239. ext h operations for writing user defined serialization and deserialization func tions for custom blocks see section 17 9 These files reside in the caml subdirectory of the Objective Caml standard library directory usually usr local lib ocam1 196 17 1 3 Linking C code with Caml code The Objective Caml runtime system comprises three main parts the bytecode interpreter the memory manager and a set of C functions that implement the primitive operations Some bytecode instructions are provided to call these C functions designated by their offset in a table of functions the table of primitives In the default mode the Caml linker produces bytecode for the standard runtime system with a standard set of primitives References to primitives that are not in this standard set result in the unavailable C primitive error In the custom runtime mode the Caml linker scans the object files and determines the set of required primitives Then it builds a suitable runtime system by calling the native code linker with e the table of the required primitives e a library that provides the bytecode interpreter the memory manager and the standard primitives e libraries and object code files o files mentioned on the command line for the Caml linker that provide implementations for the user s primitives This builds a runtime system with the required primitives The Caml linker generates bytecode for this cu
240. external value name typexpr external declaration implements value name as the external function specified in external declaration see chapter 17 Type definitions A definition of one or several type components is written type typedef and typedef and consists of a sequence of mutually recursive definitions of type names Exception definitions Exceptions are defined with the syntax exception constr decl or exception constr name constr Class definitions A definition of one or several classes is written class class binding and class binding and consists of a sequence of mutually recursive definitions of class names Class definitions are described more precisely in section 6 9 3 Class type definitions A definition of one or several classes is written class type classtype def and classtype def and consists of a sequence of mutually recursive definitions of class type names Class type definitions are described more precisely in section 6 9 5 Module definitions The basic form for defining a module component is module module name module expr which evaluates module expr and binds the result to the name module name One can write module module name module type module expr instead of module module name module expr module type Another derived form is module module name name module type namen module type module expr which is equivalent to module module name functor name module type
241. f a x computes f a 0 f a 1 a n 1 x where n is the length of the array a Sorting val val sort cmp a gt a gt int gt a array gt unit P y Sort an array in increasing order according to a comparison function The comparison function must return 0 if it arguments compare as equal a positive integer if the first is greater and a negative integer if the first is smaller For example the compare function is a suitable comparison function After calling Array sort the array is sorted in place in increasing order Array sort is guaranteed to run in constant heap space and logarithmic stack space The current implementation uses Heap Sort It runs in constant stack space stable_sort cmp a gt a gt int gt a array gt unit Same as Array sort but the sorting algorithm is stable and not guaranteed to use a fixed amount of heap memory The current implementation is Merge Sort It uses n 2 words of heap space where n is the length of the array It is faster than the current implementation of Array sort Chapter 19 The standard library 243 19 3 Module Buffer extensible string buffers This module implements string buffers that automatically expand as necessary It provides accumulative concatenation of strings in quasi linear time instead of quadratic time when strings are concatenated pairwise type t val val val val val val val val The
242. f given More precisely we have the following four situations Abstract type no equation no representation Names that are defined as abstract types in a signature can be implemented in a matching structure by any kind of type definition provided it has the same number of type param eters The exact implementation of the type will be hidden to the users of the structure In particular if the type is implemented as a variant type or record type the associated constructors and fields will not be accessible to the users if the type is implemented as an abbreviation the type equality between the type name and the right hand side of the abbre viation will be hidden from the users of the structure Users of the structure consider that type as incompatible with any other type a fresh type has been generated Type abbreviation an equation typexp no representation The type name must be implemented by a type compatible with typexp All users of the structure know that the type name is compatible with typexp New variant type or record type no equation a representation The type name must be implemented by a variant type or record type with exactly the constructors or fields specified All users of the structure have access to the constructors or fields and can use them to create or inspect values of that type However users of the structure consider that type as incompatible with any other type a fresh type has been generated Re expor
243. f it were of length len val print_int int gt unit Print an integer in the current box val print_float float gt unit Print a floating point number in the current box val print_char char gt unit Print a character in the current box val print_bool bool gt unit Print an boolean in the current box Break hints val print_space unit gt unit print_space is used to separate items typically to print a space between two words It indicates that the line may be split at this point It either prints one space or splits the line It is equivalent to print_break 1 0 val print_cut unit gt unit print_cut is used to mark a good break position It indicates that the line may be split at this point It either prints nothing or splits the line This allows line splitting at the current point without printing spaces or adding indentation It is equivalent to print_break 0 0 val print_break int gt int gt unit Insert a break hint in a pretty printing box print_break nspaces offset indicates that the line may be split a newline character is printed at this point if the contents of the current box does not fit on one line If the line is split at that point offset is added to the current indentation If the line is not split nspaces spaces are printed Chapter 19 The standard library 249 val print_flush unit gt unit Flush the pretty printer all opened boxes are closed and
244. f socket kinds specifying the semantics of communications Chapter 20 The unix library Unix system calls 311 type sockaddr ADDR_UNIX of string ADDR_INET of inet_addr int The type of socket addresses ADDR_UNIX name is a socket address in the Unix domain name is a file name in the file system ADDR_INET addr port is a socket address in the Internet domain addr is the Internet address of the machine and port is the port number val socket domain socket_domain gt kind socket_type gt protocol int gt file_descr Create a new socket in the given domain and with the given kind The third argument is the protocol type 0 selects the default protocol for that kind of sockets val socketpair domain socket_domain gt kind socket_type gt protocol int gt file_descr file_descr Create a pair of unnamed sockets connected together val accept file_descr gt file_descr sockaddr Accept connections on the given socket The returned descriptor is a socket connected to the client the returned address is the address of the connecting client val bind file_descr gt addr sockaddr gt unit Bind a socket to an address val connect file_descr gt addr sockaddr gt unit Connect a socket to an address val listen file_descr gt max int gt unit Set up a socket for receiving connection requests The integer argument is the maximal number of pending requests type shutdown_command SHUTDOWN_REC
245. f the result tail return rT It would be incorrect to perform Field r 1 tail directly because the allocation of tail has taken place since r was allocated tail is not registered as a root because there is no allocation between the assignment where it takes its value and the modify statement that uses the value 17 6 A complete example This section outlines how the functions from the Unix curses library can be made available to Objective Caml programs First of all here is the interface curses mli that declares the curses primitives and data types type window The type window remains abstract external initscr unit gt window curses_initscr external endwin unit gt unit curses_endwin external refresh unit gt unit curses_refresh external wrefresh window gt unit curses_wrefresh external newwin int gt int gt int gt int gt window curses_newwin external mvwin window gt int gt int gt unit curses_mvwin external addch char gt unit curses_addch external mvwaddch window gt int gt int gt char gt unit curses_mvwaddch external addstr string gt unit curses_addstr external mvwaddstr window gt int gt int gt string gt unit curses_mvwaddstr lots more omitted To compile this interface ocamlc c curses mli To implement these functions we just have to provide the stub code the core functions are already implemente
246. fault 20 lines of the current module are displayed starting 10 lines before the current position source filename Read debugger commands from the script filename 15 10 Running the debugger under Emacs The most user friendly way to use the debugger is to run it under Emacs See the file emacs README in the distribution for information on how to load the Emacs Lisp files for Caml support The Caml debugger is started under Emacs by the command M x camldebug with argument the name of the executable file progname to debug Communication with the debugger takes place in an Emacs buffer named camldebug progname The editing and history facilities of Shell mode are available for interacting with the debugger 186 In addition Emacs displays the source files containing the current event the current posi tion in the program execution and highlights the location of the event This display is updated synchronously with the debugger action The following bindings for the most common debugger commands are available in the camldebug progname buffer C c C s command step execute the program one step forward C c C k command backstep execute the program one step backward C c C n command next execute the program one step forward skipping over function calls Middle mouse button command display display named value n under mouse cursor support incremental browsing of large data structures C c C p command print print v
247. float gt float float modf f returns the pair of the fractional and integral part of f float int gt float float_of_int int gt float Convert an integer to floating point truncate float gt int int_of_float float gt int Truncate the given floating point number to an integer The result is unspecified if it falls outside the range of representable integers String operations val More string operations are provided in module String string gt string gt string String concatenation Chapter 18 The core library 229 Character operations More character operations are provided in module Char val int_of_char char gt int Return the ASCII code of the argument val char_of_int int gt char Return the character with the given ASCII code Raise Invalid_argument char_of_int if the argument is outside the range 0 255 Unit operations val ignore a gt unit Discard the value of its argument and return For instance ignore f x discards the result of the side effecting function f It is equivalent to f x except that only a partial application warning may be generated String conversion functions val string_of_bool bool gt string Return the string representation of a boolean val bool_of_string string gt bool Convert the given string to a boolean Raise Invalid_argument bool_of_string if the string is not true or false val string_of_int int g
248. formation about the pro files Full support for gprof is only available for certain platforms currently Intel x86 Linux and Alpha Digital Unix On other platforms the p option will result in a less precise profile no call graph information only a time profile Windows The p option does not work under Windows pp command Cause the compiler to call the given command as a preprocessor for each source file The output of command is redirected to an intermediate file which is compiled If there are no compilation errors the intermediate file is deleted afterwards The name of this file is built from the basename of the source file with the extension ppi for an interface m1i file and ppo for an implementation m1 file rectypes Allow arbitrary recursive types during type checking By default only recursive types where the recursion goes through an object type are supported S Keep the assembly code produced during the compilation The assembly code for the source file x ml is saved in the file z s thread Compile or link multithreaded programs in combination with the threads library described Chapter 11 Native code compilation ocamlopt 155 in chapter 23 What this option actually does is select a special thread safe version of the standard library unsafe Turn bound checking off on array and string accesses the v i and s i constructs Programs compiled with unsafe are therefore faster but unsafe anyt
249. from token stream to for instance int and would have rules such as let parse_expr parser lt Int n gt gt n lt Kwd n parse_expr Kwd gt gt n lt n1 parse_expr n2 parse_remainder n1 gt gt n2 and parse_remainder n1 parser lt Kwd n2 parse_expr gt gt ni n2 19 11 Module Hashtbl hash tables and hash functions Hash tables are hashed association tables with in place modification 260 Generic interface type a b t val val val val val val val val The type of hash tables from type a to type b create int gt a b t Hashtbl create n creates a new empty hash table with initial size n For best results n should be on the order of the expected number of elements that will be in the table The table grows as needed so n is just an initial guess clear a b t gt unit Empty a hash table add a b t gt key a gt data b gt unit Hashtbl add tbl x y adds a binding of x to y in table tbl Previous bindings for x are not removed but simply hidden That is after performing Hashtbl remove tbl x the previous binding for x if any is restored Same behavior as with association lists find Ca b t gt a gt b Hashtbl find tbl x returns the current binding of x in tbl or raises Not_found if no such binding exists find_all a b t gt a gt b list Hashtbl find_a
250. functions defined by the generated scanners The lexer buffer holds the current state of the scanner plus a function to refill the buffer from the input val from_channel in_channel gt lexbuf Create a lexer buffer on the given input channel Lexing from_channel inchan returns a lexer buffer which reads from the input channel inchan at the current reading position val from_string string gt lexbuf Create a lexer buffer which reads from the given string Reading starts from the first character in the string An end of input condition is generated when the end of the string is reached val from_function buf string gt len int gt int gt lexbuf Create a lexer buffer with the given function as its reading method When the scanner needs more characters it will call the given function giving it a character string s and a character count n The function should put n characters or less in s starting at character number 0 and return the number of characters provided A return value of 0 means end of input Functions for lexer semantic actions The following functions can be called from the semantic actions of lexer definitions the ML code enclosed in braces that computes the value returned by lexing functions They give access to the character string matched by the regular expression associated with the semantic action These functions must be applied to the argument lexbuf which in the code generated by ocamllex is bou
251. g Caml functions to be called from C operations on file names memory management control and statistics a catch all exception handler system interface 19 1 Module Arg parsing of command line arguments Chapter 19 The standard library 239 This module provides a general mechanism for extracting options and arguments from the command line to the program Syntax of command lines A keyword is a character string starting with a An option is a keyword alone or followed by an argument The types of keywords are Unit Set Clear String Int Float and Rest Unit Set and Clear keywords take no argument String Int and Float keywords take the following word on the command line as an argument A Rest keyword takes the remaining of the command line as string arguments Arguments not preceded by a keyword are called anonymous arguments Examples cmd is assumed to be the command name cmd flag a unit option cmd int 1 an int option with argument 1 cmd string foobar a string option with argument foobar cmd float 12 34 a float option with argument 12 34 cmd abc three anonymous arguments a b and c cmd ab cd two anonymous arguments and a rest option with two arguments Float of float gt unit Call the function with a float argument type spec Unit of unit gt unit Call the function with unit argument Set of bool ref Set the reference to true Clear of bool ref Set the ref
252. gainst the patterns pattern to pattern If the matching against pattern succeeds the associated expression expr is evaluated and its value becomes the value of the whole try expression The evaluation of expr takes place in an environment enriched by the bindings performed during matching If several patterns match the value of expr the one that occurs first in the try expression is selected If none of the patterns matches the value of expr the exception value is raised again thereby transparently passing through the try construct 6 7 3 Operations on data structures Products The expression expr expr evaluates to the n tuple of the values of expressions expr to expr The evaluation order for the subexpressions is not specified 106 Variants The expression ncconstr expr evaluates to the variant value whose constructor is ncconstr and whose argument is the value of expr For lists some syntactic sugar is provided The expression expr exprs stands for the con structor applied to the argument expr expr and therefore evaluates to the list whose head is the value of expr and whose tail is the value of expr The expression expr 3 expr is equivalent to expr expr and therefore evaluates to the list whose elements are the values of expr to expr Polymorphic variants The expression tag name expr evaluates to the variant value whose tag is tag name and whose argument
253. ges the underlying file is not affected Genarray map_file is much more efficient than reading the whole file in a big array modifying that big array and writing it afterwards To adjust automatically the dimensions of the big array to the actual size of the file the major dimension that is the first dimension for an array with C layout and the last dimension for an array with Fortran layout can be given as 1 Genarray map_file then determines the major dimension from the size of the file The file must contain an integral number of sub arrays as determined by the non major dimensions otherwise Failure is raised If all dimensions of the big array are given the file size is matched against the size of the big array If the file is larger than the big array only the initial portion of the file is mapped to the big array If the file is smaller than the big array the file is automatically grown to the size of the big array This requires write permissions on fd One dimensional arrays The Array1 structure provides operations similar to those of Genarray but specialized to the case of one dimensional arrays The Array2 and Array3 structures below provide operations specialized for two and three dimensional arrays Statically knowing the number of dimensions of the array allows faster operations and more precise static type checking 364 module Array1 sig type Ca b c t The type of one dimensional big arrays whose e
254. get_x class a circle c a object constraint a point val mutable center c method center center method set_center c center lt c method move center move end class a circle Chapter 3 Objects in Caml 47 2a gt object constraint a point val mutable center a method center a method move int gt unit method set_center a gt unit end The class colored_circle is a specialized version of class circle which requires the type of the center to unify with colored_point and adds a method color Note that when specializing a parameterized class the instance of type parameter must always be explicitly given It is again written inside and class a colored_circle c object constraint a colored_point inherit a circle c method color center color end class a colored_circle 2a gt object constraint a colored_point val mutable center a method center a method color string method move int gt unit method set_center a gt unit end 3 10 Using coercions Subtyping is never implicit There are however two ways to perform subtyping The most general construction is fully explicit both the domain and the codomain of the type coercion must be given We have seen that points and colored points have incompatible types For instance they cannot be mixed in the same list Howe
255. gt float lt fun gt HH H OH H FH eval x 1 0 y 3 14 Prod Sum Var x Const 2 0 Var y float 9 420000 Now for a real symbolic processing we define the derivative of an expression with respect to a variable dv let rec deriv exp dv match exp with Const c gt Const 0 0 Var v gt if v dv then Const 1 0 else Const 0 0 Sum f g gt Sum deriv f dv deriv g dv Diff f g gt Diff deriv f dv deriv g dv Prod f g gt Sum Prod f deriv g dv Prod deriv f dv g Quot f g gt Quot Diff Prod deriv f dv g Prod f deriv g dv Prod g g H H HH HF H val deriv expression gt string gt expression lt fun gt deriv Quot Const 1 0 Var x x expression Quot Diff Prod Const 0 000000 Var x Prod Const 1 000000 Const 1 000000 Prod Var x Var x 1 8 Pretty printing and parsing As shown in the examples above the internal representation also called abstract syntax of expres sions quickly becomes hard to read and write as the expressions get larger We need a printer and a parser to go back and forth between the abstract syntax and the concrete syntax which in the case of expressions is the familiar algebraic notation e g 2 x 1 For the printing function we take into account the usual precedence rules i e binds tighter than to avoid printing unnecessary parentheses To this end we maintain the current op
256. han or equal to its second argument The array is sorted in place val merge order a gt a gt bool gt a list gt a list gt a list Merge two lists according to the given predicate Assuming the two argument lists are sorted according to the predicate merge returns a sorted list containing the elements from the two lists The behavior is undefined if the two argument lists were not sorted 19 28 Module Stack last in first out stacks This module implements stacks LIFOs with in place modification type at The type of stacks containing elements of type a exception Empty Raised when pop is applied to an empty stack val create unit gt at Return a new stack initially empty val push a gt a t gt unit push x s adds the element x at the top of stack s val pop a t gt a pop s removes and returns the topmost element in stack s or raises Empty if the stack is empty val top a t gt a top s returns the topmost element in stack s or raises Empty if the stack is empty Chapter 19 The standard library 287 val clear a t gt unit Discard all elements from a stack val length a t gt int Return the number of elements in a stack val iter f a gt unit gt a t gt unit iter f s applies f in turn to all elements of s from the element at the top of the stack to the element at the bottom of the stack The stack itself is unchanged 19 29
257. hannel_length 233 out_channel_of_descr 300 Out_of_memory exception 223 output 233 245 output_binary_int 233 output_buffer 244 output_byte 233 output_char 232 output_string 232 output_value 233 over_max_boxes 249 pack 353 parent_dir_name 245 parse 239 Parse_error exception 280 Parsing module 279 partition 272 pause 306 peek 282 288 Pervasives module 221 pipe 304 337 pixels 353 place 354 plot 342 point_color 342 poll 336 pop 286 pos_in 235 pos_out 233 power_num 320 pp_close_box 254 pp_close_tbox 254 pp_force_newline 254 pp_get_all_formatter_output_functions 254 pp_get_ellipsis_text 254 pp_get_formatter_output_functions 254 pp_get_margin 254 pp_get_max_boxes 254 pp_get_max_indent 254 pp_open_box 254 pp_open_hbox 254 pp_open_hovbox 254 pp_open_hvbox 254 381 pp_open_tbox 254 pp_open_vbox 254 pp_over_max_boxes 254 pp_print_as 254 pp_print_bool 254 pp_print_break 254 pp_print_char 254 pp_print_cut 254 pp_print_float 254 pp_print_flush 254 pp_print_if_newline 254 pp_print_int 254 pp_print_newline 254 pp_print_space 254 pp_print_string 254 pp_print_tab 254 pp_print_tbreak 254 pp_set_all_formatter_output_functions 254 pp_set_ellipsis_text 254 pp_set_formatter_out_channel 254 pp_set_formatter_output_functions 254 pp_set_margin 254 pp_set_max_boxes 254 pp_set_max_indent 254 pp_set_tab 254 pred 225 263
258. he two components are separated by a space Either can be omitted or both Examples open_graph foo 0 connects to the display foo 0 and creates a window with the default geometry open_graph foo 0 300x100 50 0 connects to the display foo 0 and creates a window 300 pixels wide by 100 pixels tall at location 50 0 open_graph 300x100 50 0 connects to the default display and creates a window 300 pixels wide by 100 pixels tall at location 50 0 open_graph connects to the default display and creates a window with the default geometry 339 340 Windows This library is available only under the toplevel application ocamlwin exe Before using it the Caml part of this library must be loaded in core either by typing load graphics cmo in the input windows or by using the Load entry of the File menu The screen coordinates are interpreted as shown in the figure below Notice that the coordinate system used is the same as in mathematics y increases from the bottom of the screen to the top of the screen and angles are measured counterclockwise in degrees Drawing is clipped to the screen y Screen pixel at x y x size_x 24 1 Module Graphics machine independent graphics primitives exception Graphic_failure of string Raised by the functions below when they encounter an error Initializations val open_graph string gt unit Show the graphics window or switch the screen to graphic mode
259. hem Otherwise they will be kept and the result of the function will still be a function of the missing optional parameters In the strict or commuting label mode parameters and arguments are matched according to their labels The order is irrelevent except if several arguments have the same label or no label The criterion for defaulting missing optional arguments is whether a non labeled parameter 102 following them in f was matched by an argument or not If some parameters were not matched in the process the result will be a new function from these parameters to the body of f Function definition Two syntactic forms are provided to define functions The first form is introduced by the keyword function function pattern gt expr pattern gt expr This expression evaluates to a functional value with one argument When this function is applied to a value v this value is matched against each pattern pattern to pattern If one of these matchings succeeds that is if the value v matches the pattern pattern for some i then the expression expr associated to the selected pattern is evaluated and its value becomes the value of the function application The evaluation of expr takes place in an environment enriched by the bindings performed during the matching If several patterns match the argument v the one that occurs first in the function definition is selected If none of the patterns matches the argument the except
260. hen an integer offset and a closing gt character flush the pretty printer as with print_flush flush the pretty printer and output a new line as with print_newline Chapter 19 The standard library 255 lt n gt print the following item as if it were of length n Hence printf lt 0 gt s arg is equivalent to print_as 0 arg If lt n gt is not followed by a conversion specification then the following character of the format is printed as if it were of length n print a plain character Example printf s d x 1 is equivalent to open_box print_string x print_space print_int 1 close_box It prints x 1 within a pretty printing box val bprintf Buffer t gt a formatter unit format gt a Same as fprintf but instead of printing on a formatter writes into the buffer argument val printf a formatter unit format gt a Same as fprintf but output on std_formatter val eprintf a formatter unit format gt a Same as fprintf but output on err_formatter val sprintf a unit string format gt a Same as printf but instead of printing on a formatter return a string containing the result of formatting the arguments 19 9 Module Gc memory management control and statistics finalised values type stat minor_words int promoted_words int major_words int minor_collections int major_collections int heap_wor
261. hing can happen if the program accesses an array or string outside of its bounds v Print the version number of the compiler w warning list Enable or disable warnings according to the argument warning list The argument is a string of one or several characters with the following meaning for each character A a enable disable all warnings F f enable disable warnings for partially applied functions ie f x expr where the appli cation f x has a function type M m enable disable warnings for overriden methods P p enable disable warnings for partial matches missing cases in pattern matchings S s enable disable warnings for statements that do not have type unit e g exprl expr2 when ezpr1 does not have type unit U u enable disable warnings for unused redundant match cases V v enable disable warnings for hidden instance variables X x enable disable all other warnings The default setting is w A all warnings enabled 11 3 Common errors The error messages are almost identical to those of ocamlc See section 8 4 11 4 Compatibility with the bytecode compiler This section lists the known incompatibilities between the bytecode compiler and the native code compiler Except on those points the two compilers should generate code that behave identically e The following operations abort the program either by printing an error message or just via an hardware trap or fatal Unix signal instead of raising an exc
262. hod get string gt int gt char method print unit method repr string method set string gt int gt char gt unit method sub int gt int gt a end Another constructor of the class string can be defined to return an uninitialized string of a given length class cstring n ostring String create n class cstring int gt ostring Here exposing the representation of strings is probably harmless We do could also hide the representation of strings as we hid the currency in the class money of section 3 15 Stacks There is sometimes an alternative between using modules or classes for parametric data types Indeed there are situations when the two approaches are quite similar For instance a stack can be straightforwardly implemented as a class exception Empty exception Empty class a stack object val mutable 1 a list method push x 1 lt x 1 method pop match 1 with gt raise Empty a 1 gt 1 lt 1 a method clear 1 lt method length List length 1 end class a stack object val mutable 1 a list method clear unit method length int method pop a method push a gt unit end However writing a method for iterating over a stack is more problematic A method fold would have type b gt a gt b gt b gt b Here a is the parameter of the stack The parameter b is not related to
263. htbl int gt a b hash_table 5 2 3 Sets Implementing sets leads to another difficulty Indeed the method union needs to be able to access the internal representation of another object of the same class This is another instance of friend functions as seen in section 3 15 Indeed this is the same mechanism used in the module Set in the absence of objects In the object oriented version of sets we only need to add an additional method tag to return the representation of a set Since sets are parametric in the type of elements the method tag has a parametric type a tag concrete within the module definition but abstract in its signature From outside it will then be guaranteed that two objects with a method tag of the same type will share the same representation module type SET sig type a tag class a c object b method is_empty bool method mem a gt bool method add a gt b method union b gt b method iter a gt unit gt unit method tag a tag end end module Set SET struct let rec merge 11 12 match 11 with gt 12 ht t1 gt match 12 with gt 11 h2 t2 gt HH HHH HH HH FH OH HH FH FH OH FH HHHH if hi lt h2 then hi merge t1 12 Chapter 5 Advanced examples with classes and modules 79 else if hi gt h2 then h2 merge 11 t2 else merge ti 12 type a tag a list
264. ified while other points will be set to the color of the corresponding point in the image This allows superimposing an image over an existing background val make_image color array array gt image Convert the given color matrix to an image Each sub array represents one horizontal line All sub arrays must have the same length otherwise exception Graphic_failure is raised val dump_image image gt color array array Convert an image to a color matrix val draw_image image gt x int gt y int gt unit Draw the given image with lower left corner at the given point val get_image x int gt y int gt w int gt h int gt image Capture the contents of a rectangle on the screen as an image The parameters are the same as for fill_rect val create_image w int gt h int gt image create_image w h returns a new image w pixels wide and h pixels tall to be used in conjunction with blit_image The initial image contents are random except that no point is transparent val blit_image image gt x int gt y int gt unit blit_image img x y copies screen pixels into the image img modifying img in place The pixels copied are those inside the rectangle with lower left corner at x y and width and height equal to those of the image Pixels that were transparent in img are left unchanged Chapter 24 The graphics library 345 Mouse and keyboard events type status mouse_x int X coordinate of the mouse mouse_
265. ified parts of the program and saves them in a file called ocamlprof dump in the current directory The ocamlprof dump file is written only if the program terminates normally by calling exit or by falling through It is not written if the program terminates with an uncaught exception If a compatible dump file already exists in the current directory then the profiling information is accumulated in this dump file This allows for instance the profiling of several executions of a program on different inputs 16 3 Printing profiling information The ocamlprof command produces a source listing of the program modules where execution counts have been inserted as comments For instance ocamlprof foo ml prints the source code for the foo module with comments indicating how many times the functions in this module have been called Naturally this information is accurate only if the source file has not been modified since the profiling execution took place The following options are recognized by ocamlprof f dumpfile Specifies an alternate dump file of profiling information F string Specifies an additional string to be output with profiling information By default ocamlprof will annotate programs with comments of the form n where n is the counter value for a profiling point With option F s the annotation will be sn 16 4 Time profiling Profiling with ocamlprof only records execution counts not the actual time spent int
266. ig type element Elt t concrete type set abstract val empty set val add element gt set gt set val member element gt set gt bool end module type SETFUNCTOR functor Elt ORDERED_TYPE gt sig type element Elt t and set val empty set val add element gt set gt set val member element gt set gt bool end module AbstractSet Set SETFUNCTOR module AbstractSet SETFUNCTOR module AbstractStringSet AbstractSet OrderedString module AbstractStringSet sig type element OrderedString t and set AbstractSet OrderedString set val empty set val add element gt set gt set val member element gt set gt bool end AbstractStringSet add gee AbstractStringSet empty AbstractStringSet set lt abstr gt In an attempt to write the type constraint above more elegantly one may wish to name the signature of the structure returned by the functor then use that signature in the constraint module type SET sig type element type set val empty set val add element gt set gt set val member element gt set gt bool HH H HH H H OF end module type SET sig type element and set val empty set val add element gt set gt set val member element gt set gt bool end module WrongSet Set functor Elt ORDERED_TYPE gt SET module WrongSet functor Elt ORDERE
267. ignature sig type t module M sig type u end end then S with type t int denotes the signature sig type t int module M sig type u end end and S with module M N denotes the signature sig type t module M sig type u N u end end A functor taking two arguments of type S that share their t component is written functor A S B S with type t A t 6 11 Module expressions module implementations Module expressions are the module level equivalent of value expressions they evaluate to modules thus providing implementations for the specifications expressed in module types 122 module expr module path struct definition end functor module name module type gt module expr module expr module expr module expr module expr module type definition let rec let binding and let binding external value name typexpr external declaration type definition exception definition class definition classtype definition module module name module name module type module type module expr module type modtype name module type open module path 6 11 1 Simple module expressions The expression module path evaluates to the module bound to the name module path The expression module expr evaluates to the same module as module expr The expression module expr module type checks that the type of module expr is a subtype of module type that is that all components specifie
268. imes backstep count Run the program backward and stop at the previous event With an argument do it count times next count Run the program and stop at the next event skipping over function calls With an argument do it count times previous count Run the program backward and stop at the previous event skipping over function calls With an argument do it count times finish Run the program until the current function returns start Run the program backward and stop at the first event before the current function invocation 15 4 4 Time travel You can jump directly to a given time without stopping on breakpoints using the goto command As you move through the program the debugger maintains an history of the successive times you stop at The last command can be used to revisit these times each last command moves one step back through the history That is useful mainly to undo commands such as step and next goto time Jump to the given time last count Go back to the latest time recorded in the execution history With an argument do it count times set history size Set the size of the execution history 180 15 4 5 Killing the program kill Kill the program being executed This command is mainly useful if you wish to recompile the program without leaving the debugger 15 5 Breakpoints A breakpoint causes the program to stop whenever a certain point in the program is reached It can be set in several
269. implement these two tasks The first function actually implements the primitive taking native C values as arguments and returning a native C value The second function often called the stub code is a simple wrapper around the first function that converts its arguments from Caml values to C values call the first function and convert the returned C value to Caml value For instance here is the stub code for the input primitive value input value channel value buffer value offset value length return Val_long getblock struct channel channel amp Byte buffer Long_val offset Long_val length Here Val_long Long_val and so on are conversion macros for the type value that will be described later The hard work is performed by the function getblock which is declared as long getblock struct channel channel char p long n To write C code that operates on Objective Caml values the following include files are provided Include file Provides caml mlvalues h definition of the value type and conversion macros caml alloc h allocation functions to create structured Caml objects caml memory h miscellaneous memory related functions and macros for GC interface in place modification of structures etc caml fail h functions for raising exceptions see section 17 4 5 caml callback h callback from C to Caml see section 17 7 caml custom h operations on custom blocks see section 17 9 caml int
270. in their output so that error messages produced by the compiler contain line numbers and file names referring Chapter 6 The Objective Caml language 89 to the source file before preprocessing instead of after preprocessing A line number directive is composed of a sharp sign followed by a positive integer the source line number optionally followed by a character string the source file name Line number directives are treated as blank characters during lexical analysis 6 2 Values This section describes the kinds of values that are manipulated by Caml Light programs 6 2 1 Base values Integer numbers Integer values are integer numbers from 2 to 230 1 that is 1073741824 to 1073741823 The implementation may support a wider range of integer values on 64 bit platforms the current implementation supports integers ranging from 2 to 2 1 Floating point numbers Floating point values are numbers in floating point representation The current implementation uses double precision floating point numbers conforming to the IEEE 754 standard with 53 bits of mantissa and an exponent ranging from 1022 to 1023 Characters Character values are represented as 8 bit integers between 0 and 255 Character codes between 0 and 127 are interpreted following the ASCII standard The current implementation interprets character codes between 128 and 255 following the ISO 8859 1 standard Character strings String values a
271. incompatible internally normal and optional arguments are different a type error occurs when applying bump_it to the real bump We will not try here to explain in detail how type inference works One must just understand that there is not enough information in the above program to deduce the correct type of bump That is there is no way to know whether an argument is optional or not or which is the correct order for commuting label mode by looking only at how a function is applied The strategy used by the compiler is to assume that there are no optional arguments and that applications are done in the right order The right way to solve this problem is to add a type annotation to the argument bump let bump_it bump step int gt int gt int x bump step 2 x val bump_it step int gt int gt int gt int gt int lt fun gt bump_it bump 1 int 8 In practive such problems appear mostly when using objects whose methods have optional argu ments so that writing the type of object arguments is often a good idea Normally the compiler generates a type error if you attempt to pass to a function a parameter whose type is different from the expected one However in the specific case where the expected type is a non labeled function type and the argument is a function expecting optional parameters the compiler will attempt to transform the argument to have it match the expected type by passing None fo
272. ing matched_group n s returns the substring of s that was matched by the nth group of the regular expression during the latest string_match search_forward or search_backward The user must make sure that the parameter s is the same string that was passed to the matching or searching function matched_group n s raises Not_found if the nth group of the regular expression was not matched This can happen with groups inside alternatives options or repetitions For instance the empty string will match Ca but matched_group 1 will raise Not_found because the first group itself was not matched val group_beginning int gt int val group_end int gt int group_beginning n returns the position of the first character of the substring that was matched by the nth group of the regular expression group_end n returns the position of the character following the last character of the matched substring Both functions raise Not_found if the nth group of the regular expression was not matched Replacement val global_replace pat regexp gt templ string gt string gt string global_replace regexp templ s returns a string identical to s except that all substrings of s that match regexp have been replaced by templ The replacement template templ can contain 1 2 etc these sequences will be replaced by the text matched by the corresponding group in the regular expression O stands for the text matched by the whole regular exp
273. ing on the operating system some translations may take place during input For instance under Windows end of lines will be translated from r n to n This function has no effect under operating systems that do not distinguish between text mode and binary mode 236 References type a ref mutable contents a The type of references mutable indirection cells containing a value of type a val ref a gt a ref Return a fresh reference containing the given value val a ref gt a Ir returns the current contents of reference r Equivalent to fun r gt r contents val a ref gt a gt unit r a stores the value of a in reference r Equivalent to fun r v gt r contents lt v val incr int ref gt unit Increment the integer contained in the given reference Equivalent to fun r gt r succ r val decr int ref gt unit Decrement the integer contained in the given reference Equivalent to fun r gt r pred r Program termination val exit int gt a Flush all pending writes on stdout and stderr and terminate the process returning the given status code to the operating system usually 0 to indicate no errors and a small positive integer to indicate failure An implicit exit 0 is performed each time a program terminates normally but not if it terminates because of an uncaught exception val at_exit unit gt unit gt unit Register the given funct
274. interactive use of the unix library do ocamlmktop o mytop unix cma mytop MacOS A fairly complete emulation of the Unix system calls is provided in the MacOS version of Objective Caml The end of this chapter gives more information on the functions that are not supported under MacOS Windows A fairly complete emulation of the Unix system calls is provided in the Windows version of Objective Caml The end of this chapter gives more information on the functions that are not supported under Windows 20 1 Module Unix interface to the Unix system Error report type error Errors defined in the POSIX standard 295 296 E2BIG EACCES EAGAIN EBADF EBUSY ECHILD EDEADLK EDOM EEXIST EFAULT EFBIG EINTR EINVAL EIO EISDIR EMF ILE EMLINK ENAMETOOLONG ENFILE ENODEV ENOENT ENOEXEC ENOLCK ENOMEM ENOSPC ENOSYS ENOTDIR ENOTEMPTY ENOTTY ENXIO EPERM EPIPE ERANGE EROFS ESPIPE ESRCH EXDEV x x x Cx x x Cx x x x x x Cx Cx x x Cx Cx x x Cx x x Cx Cx x x Cx Cx x Cx x Cx Cx x Cx Cx Argument list too long Permission denied Resource temporarily unavailable try again Bad file descriptor Resource unavailable No child process Resource deadlock would occur Domain error for math functions etc File exists Bad address File too large Function interrupted by signal Invalid argument Hardware I O error Is a dire
275. interface in the file x cmi The interface produced is identical to that produced by the bytecode compiler ocamlc e Arguments ending in ml are taken to be source files for compilation unit implementations Implementations provide definitions for the names exported by the unit and also contain expressions to be evaluated for their side effects From the file x m1 the ocamlopt compiler produces two files z o containing native object code and x cmx containing extra informa tion for linking and optimization of the clients of the unit The compiled implementation should always be referred to under the name z cmx when given a o file ocamlopt assumes that it contains code compiled from C not from Caml The implementation is checked against the interface file x mli if it exists as described in the manual for ocamlc chapter 8 151 152 Arguments ending in cmx are taken to be compiled object code These files are linked together along with the object files obtained by compiling m1 arguments if any and the Caml Light standard library to produce a native code executable program The order in which cmx and ml arguments are presented on the command line is relevant compilation units are initialized in that order at run time and it is a link time error to use a component of a unit before having initialized it Hence a given x cmx file must come before all cmx files that refer to the unit z Arguments ending in cmxa are taken t
276. interfaces 349 add_num 320 add_string 243 add_substring 243 alarm 307 allocated_bytes 258 allow_unsafe_modules 350 always 336 append 241 269 appname_get 352 appname_set 352 approx_num_exp 322 approx_num_fix 322 Arg module 238 argv 291 arith_status 322 Arith_status module 322 array 286 Array module 240 Array1 module 364 arrayl_of_genarray 369 Array2 module 365 array2_of_genarray 369 Array3 module 366 array3_of_genarray 369 asin 227 asr operator 226 Assert_failure exception 127 223 assoc 272 assq 272 at_exit 236 atan 227 atan2 227 auto_synchronize 346 background 341 376 Bad exception 240 basename 246 big_int_of_num 322 Bigarray module 358 bind 311 355 bind_class 356 bind_tag 356 bits 283 black 341 blit 241 289 293 blit_image 344 blue 341 bool_of_string 229 bounded_full_split 328 bounded_split 328 bounded_split_delim 328 bprintf 255 281 break 356 Break exception 292 broadcast 335 Buffer module 243 button_down 345 c_layout 360 Callback module 244 capitalize 290 catch 280 catch_break 293 ceil 228 ceiling num 320 channel 245 char 359 Char module 244 char_of_int 229 chdir 291 303 check 293 check_suffix 246 chmod 302 choose 336 chop_extension 246 chop_suffix 246 chown 302 chr 244 chroot 303 clear 243 260 282 287 clear_available_units 350 clear_close_on_exec 30
277. io h gt include lt string h gt include lt caml mlvalues h gt include lt caml callback h gt int fib int n static value fib_closure NULL if fib_closure NULL fib_closure caml_named_value fib return Int_val callback fib_closure Val_int n char format_result int n static value format_result_closure NULL if format_result_closure NULL format_result_closure caml_named_value format_result return strdup String_val callback format_result_closure Val_int n We copy the C string returned by String_val to the C heap so that it remains valid after garbage collection We now compile the Caml code to a C object file and put it in a C library along with the stub code in modwrap c and the Caml runtime system ocamlc custom output obj o modcaml o mod ml ocamlc c modwrap c cp usr local lib ocaml libcamlrun a mod a ar r mod a modcaml o modwrap o One can also use ocamlopt output obj instead of ocamlc custom output obj In this case replace libcamlrun a the bytecode runtime library by libasmrun a the native code runtime library Now we can use the two fonctions fib and format_result in any C program just like regular C functions Just remember to call caml_startup once before 214 File main c a sample client for the Caml functions include lt stdio h gt int main int argc char argv int result Initialize Caml code caml_startup
278. ion Match_failure is raised The other form of function definition is introduced by the keyword fun fun parameter parameter gt expr This expression is equivalent to fun parameter gt fun parameter gt expr Functions of the form fun optlabel pattern expry gt expr are equivalent to fun optlabel x gt let pattern match x with Some x gt x None gt expr in expr where x is a fresh variable When expr will be evaluated is left unspecified After these two transformations expressions are of the form fun label pattern gt fun label pattern gt expr If we ignore labels which will only be meaningful at function application this is equivalent to function pattern gt function pattern gt expr That is the fun expression above evaluates to a curried function with n arguments after applying this function n times to the values v Um the values will be matched in parallel against the patterns pattern pattern If the matching succeeds the function returns the value of expr in an environment enriched by the bindings performed during the matchings If the matching fails the exception Match_failure is raised Chapter 6 The Objective Caml language 103 Guards in pattern matchings Cases of a pattern matching in the function fun match and try constructs can include guard expressions which are arbitrary boolean expressions that must evaluate to true for the match case to be selected
279. ion functions can be provided Identifiers starting with _ an underscore character are reserved for the Objective Caml runtime system do not use them for your custom data We recommend to use a URL 218 http mymachine mydomain com mylibrary version number or a Java style package name com mydomain mymachine mylibrary version number as identifiers to minimize the risk of identifier collision 17 9 6 Finalized blocks Custom blocks generalize the finalized blocks that were present in Objective Caml prior to version 3 00 For backward compatibility the format of custom blocks is compatible with that of finalized blocks and the alloc_final function is still available to allocate a custom block with a given finalization function but default comparison hashing and serialization functions alloc_final n f used max returns a fresh custom block of size n words with finalization function f The first word is reserved for storing the custom operations the other n 1 words are available for your data The two parameters used and maz are used to control the speed of garbage collection as described for alloc_custom Part IV The Objective Caml library 219 Chapter 18 The core library This chapter describes the functions provided by the Objective Caml core library module module Pervasives This module is special in two ways e It is automatically linked with the user s object code files by the ocamlc command chapter 8 e
280. ion of marshaled values is not human readable and uses bytes that are not printable characters Therefore input and output channels used in conjunction with Marshal to_channel and Marshal from_channel must be opened in binary mode using e g open_out_bin or open_in_bin channels opened in text mode will cause unmarshaling errors on platforms where text channels behave differently than binary channels e g Windows type extern_flags No_sharing Don t preserve sharing Closures Send function closures The flags to the Marshal to_ functions below val to_channel out_channel gt a gt mode extern_flags list gt unit Marshal to_channel chan v flags writes the representation of v on channel chan The flags argument is a possibly empty list of flags that governs the marshaling behavior with respect to sharing and functional values If flags does not contain Marshal No_sharing circularities and sharing inside the value v are detected and preserved in the sequence of bytes produced In particular this guarantees that marshaling always terminates Sharing between values marshaled by successive calls to Marshal to_channel is not detected though If flags contains Marshal No_sharing sharing is ignored This results in faster marshaling if v contains no shared substructures but may cause slower marshaling and larger byte representations if v actually contains sharing or even non termination if v contains cycles If flags d
281. ion to be called at program termination time The functions registered with at_exit will be called when the program executes exit They will not be called if the program terminates because of an uncaught exception The functions are called in last in first out order the function most recently added with at_exit is called first Chapter 19 The standard library This chapter describes the functions provided by the Caml Light standard library The modules from the standard library are automatically linked with the user s object code files by the ocamlc command Hence these modules can be used in standalone programs without having to add any cmo file on the command line for the linking phase Similarly in interactive use these globals can be used in toplevel phrases without having to load any cmo file in memory Unlike the Pervasive module from the core library the modules from the standard library are not automatically opened when a compilation starts or when the toplevel system is launched Hence it is necessary to use qualified identifiers to refer to the functions provided by these modules or to add open directives Conventions For easy reference the modules are listed below in alphabetical order of module names For each module the declarations from its signature are printed one by one in typewriter font followed by a short comment All modules and the identifiers they export are indexed at the end of this report Ove
282. is function can be used to give scheduling hints telling the scheduler that now is a good time to switch to other threads 334 23 2 Module Mutex locks for mutual exclusion Mutexes mutual exclusion locks are used to implement critical sections and protect shared mutable data structures against concurrent accesses The typical use is if m is the mutex associated with the data structure D Mutex lock m Critical section that operates over D Mutex unlock m type t The type of mutexes val create unit gt t Return a new mutex val lock t gt unit Lock the given mutex Only one thread can have the mutex locked at any time A thread that attempts to lock a mutex already locked by another thread will suspend until the other thread unlocks the mutex val try_lock t gt bool Same as try_lock but does not suspend the calling thread if the mutex is already locked just return false immediately in that case If the mutex is unlocked lock it and return true val unlock t gt unit Unlock the given mutex Other threads suspended trying to lock the mutex will restart 23 3 Module Condition condition variables to synchronize between threads Condition variables are used when one thread wants to wait until another thread has finished doing something the former thread waits on the condition variable the latter thread signals the condition when it is done Condition variables should always be protected by
283. is suitable for passign as first argument to raise_constant or raise_with_arg 19 5 Module Char character operations val code char gt int Return the ASCII code of the argument val chr int gt char Return the character with the given ASCII code Raise Invalid_argument Char chr if the argument is outside the range 0 255 val escaped char gt string Return a string representing the given character with special characters escaped following the lexical conventions of Objective Caml val lowercase char gt char val uppercase char gt char Convert the given character to its equivalent lowercase or uppercase character respectively Chapter 19 The standard library 245 19 6 Module Digest MD5 message digest This module provides functions to compute 128 bit digests of arbitrary length strings or files The digests are of cryptographic quality it is very hard given a digest to forge a string having that digest The algorithm used is MD5 type t string val val val val val val The type of digests 16 character strings string string gt t Return the digest of the given string substring string gt pos int gt len int gt t Digest substring s ofs len returns the digest of the substring of s starting at character number ofs and containing len characters channel in_channel gt len int gt t Digest channel ic len reads len characters from channel ic and returns their
284. is the value of expr Records The expression field expr field expr evaluates to the record value field v 3 fieldn vn where v is the value of expr for i 1 n The fields field to field must all belong to the same record types all fields belonging to this record type must appear exactly once in the record expression though they can appear in any order The order in which expr to expr are evaluated is not specified The expression expr field evaluates expr to a record value and returns the value associated to field in this record value The expression expr field lt expr evaluates expr to a record value which is then modified in place by replacing the value associated to field in this record by the value of exprs This operation is permitted only if field has been declared mutable in the definition of the record type The whole expression expr field lt expr evaluates to the unit value Arrays The expression expr expr evaluates to a n element array whose elements are ini tialized with the values of expr to expr respectively The order in which these expressions are evaluated is unspecified The expression expr expr returns the value of element number expr in the array denoted by expr The first element has number 0 the last element has number n 1 where n is the size of the array The exception Invalid_argument is raised if the access is out of boun
285. ive Caml as the variables BYTECCLINKOPTS for object files produced by ocamlc output obj and NATIVECCLINKOPTS for object files produced by ocamlopt output obj Currently the only ports that require special attention are e Alpha under Digital Unix Tru64 Unix with gcc object files produced by ocamlc output obj must be linked with the gcc options W1 T 12000000 W1 D 14000000 This is not necessary for object files produced by ocamlopt output obj e Windows NT the object file produced by Objective Caml have been compiled with the MT flag and therefore all other object files linked with it should also be compiled with MT 17 8 Advanced example with callbacks This section illustrates the callback facilities described in section 17 7 We are going to package some Caml functions in such a way that they can be linked with C code and called from C just like any C functions The Caml functions are defined in the following mod m1 Caml source 4 File mod ml some useful Caml functions Chapter 17 Interfacing C with Objective Caml 213 let rec fib n if n lt 2 then 1 else fib n 1 fib n 2 let format_result n Printf sprintf Result is d n n Export those two functions to C let _ Callback register fib fib let Callback register format_result format_result Here is the C stub code for calling these functions from C File modwrap c wrappers around the Caml functions include lt std
286. ize 2 lt Window 2 lt Move gt lt Window 2 lt Raise gt Position 1 Size 1 Position 1 Size 1 lt Window 2 lt Resize gt lt Window 2 lt Raise gt Position 1 Size 3 Position 1 Size 3 unit OQ Part II The Objective Caml language Chapter 6 The Objective Caml language Foreword This document is intended as a reference manual for the Objective Caml language It lists the language constructs and gives their precise syntax and informal semantics It is by no means a tutorial introduction to the language there is not a single example A good working knowledge of Caml is assumed No attempt has been made at mathematical rigor words are employed with their intuitive meaning without further definition As a consequence the typing rules have been left out by lack of the mathematical framework required to express them while they are definitely part of a full formal definition of the language Notations The syntax of the language is given in BNF like notation Terminal symbols are set in typewriter font like this Non terminal symbols are set in italic font like that Square brackets denote optional components Curly brackets denotes zero one or several repetitions of the enclosed components Curly bracket with a trailing plus sign denote one or several repetitions of the enclosed components Parentheses denote grouping 6 1 Lexical conventions Blank
287. ken defined by the generated parsing module See the description of ocamlyacc below 157 158 12 2 Syntax of lexer definitions The format of lexer definitions is as follows header let ident regexp rule entrypoint parse regexp action i genase regexp action and entrypoint parse and trailer Comments are delimited by and as in Caml 12 2 1 Header and trailer The header and trailer sections are arbitrary Caml text enclosed in curly braces Either or both can be omitted If present the header text is copied as is at the beginning of the output file and the trailer text at the end Typically the header section contains the open directives required by the actions and possibly some auxiliary functions used in the actions 12 2 2 Naming regular expressions Between the header and the entry points one can give names to frequently occurring regular expressions This is written let ident regexp In following regular expressions the identifier ident can be used as shorthand for regexp 12 2 3 Entry points The names of the entry points must be valid identifiers for Caml values starting with a lowercase letter 12 2 4 Regular expressions The regular expressions are in the style of lex with a more Caml like syntax gt char A character constant with the same syntax as Objective Caml character constants Match the denoted character Underscore Match any character
288. l expr expr The table below lists the symbols defined in the initial environment and their initial meaning See the description of the standard library module Pervasive in chapter 18 for more details Their meaning may be changed at any time using let infix op name names 108 Operator Initial meaning Integer addition infix Integer subtraction prefix Integer negation Integer multiplication Integer division Raise Division_by_zero if second argument is zero The result is unspecified if either argument is negative mod Integer modulus Raise Division_by_zero if second argument is zero The result is unspecified if either argument is negative land Bitwise logical and on integers lor Bitwise logical or on integers lxor Bitwise logical exclusive or on integers 1sl Bitwise logical shift left on integers lsr Bitwise logical shift right on integers asr Bitwise arithmetic shift right on integers Floating point addition infix Floating point subtraction prefix Floating point negation Floating point multiplication fs Floating point division xk Floating point exponentiation List concatenation String concatenation Dereferencing return the current contents of a reference Reference assignment update the reference given as first argument with the value of the second argument Structural equality test lt gt Structural inequ
289. l big array external get a b c t gt int gt int gt a Array2 get a x y also written a x y returns the element of a at coordinates x y x and y must be within the bounds of a as described for Genarray get otherwise Invalid_arg is raised external set a b c t gt int gt int gt a gt unit Array2 set a x y v or alternatively a x y lt v stores the value v at coordinates x y in a x and y must be within the bounds of a as described for Genarray set otherwise Invalid_arg is raised external sub_left Ca b c_layout t gt pos int gt len int gt a b c_layout t Extract a two dimensional sub array of the given two dimensional big array by restricting the first dimension See Genarray sub_left for more details Array2 sub_left applies only to arrays with C layout external sub_right Ca b fortran_layout t gt pos int gt len int gt a b fortran_layout t Extract a two dimensional sub array of the given two dimensional big array by restricting the second dimension See Genarray sub_right for more details Array2 sub_right applies only to arrays with Fortran layout 366 val slice_left Ca b c_layout t gt x int gt a b c_layout Array1 t Extract a row one dimensional slice of the given two dimensional big array The integer parameter is the index of the row to extract See Genarray slice_left for more details A
290. l modification of this variable by methods An instance variables can only be used in the following methods and initializers of the class Method definition Method definition is written method method name expr The definition of a method overrides any previous definition of this method The method will be public that is not private if any of the definition states so A private method method private method name expr is a method that can only be invoked on self from other methods of the current class as well as of subclasses of the current class This invocation is performed using the expression value name method name where value name is directly bound to self at the beginning of the class definition Private methods do not appear in object types 116 Some special expressions are available in method bodies for manipulating instance variables and duplicating self expr inst var name lt expr lt inst var name expr inst var name expr gt The expression inst var name lt expr modifies in place the current object by replacing the value associated to inst var name by the value of expr Of course this instance variable must have been declared mutable The expression lt inst var name expr inst var name expr gt evaluates to a copy of the current object in which the values of instance variables inst var name inst var name have been replaced by the values of the corresponding expressions expr
291. lc make runtime o home me ocamlunixrun unix cma threads cma To generate a bytecode executable that runs on this runtime system do ocamlc use runtime home me ocamlunixrun o myprog unix cma threads cma your cmo and cma files The bytecode executable myprog can then be launched as usual myprog args or home me ocamlunixrun myprog args Notice that the bytecode libraries unix cma and threads cma must be given twice when building the runtime system so that ocamlc knows which C primitives are required and also when building the bytecode executable so that the bytecode from unix cma and threads cma is actually linked in 198 17 2 The value type All Caml objects are represented by the C type value defined in the include file cam1 mlvalues h along with macros to manipulate values of that type An object of type value is either e an unboxed integer e a pointer to a block inside the heap such as the blocks allocated through one of the alloc_ functions below e a pointer to an object outside the heap e g a pointer to a block allocated by malloc or to a C variable 17 2 1 Integer values Integer values encode 31 bit signed integers 63 bit on 64 bit architectures They are unboxed unallocated 17 2 2 Blocks Blocks in the heap are garbage collected and therefore have strict structure constraints Each block includes a header containing the size of the block in words and the tag of the block The tag govern
292. le 262 int64 359 Int64 module 264 int8_signed 359 int8_unsigned 359 int_of_char 229 int_of_float 228 int_of_num 322 int_of_string 229 integer_num 320 interactive 291 invalid_arg 223 Invalid_argument exception 223 is_implicit 246 is_integer_num 320 is_relative 246 iter 242 260 270 282 287 288 348 iter2 270 iteri 242 join 332 junk 288 key_pressed 345 kill 306 332 land operator 226 last_chars 329 Lazy module 127 Lazy module 267 ldexp 228 379 le_nun 321 length 240 243 269 282 287 288 293 lexeme 268 lexeme_char 269 lexeme_end 269 lexeme_start 269 Lexing module 268 lineto 342 link 302 list 286 List module 269 listen 311 lnot 226 loadfile 349 loadfile_private 349 localtime 307 lock 334 lockf 306 log 227 log10 227 logand 263 265 278 lognot 263 266 278 logor 263 266 278 logxor 263 266 278 lor operator 226 lower_window 354 lowercase 244 290 lseek 301 1sl operator 226 lsr operator 226 1stat 302 1t_num 321 lxor operator 226 magenta 341 mainLoop 352 major 257 make 240 289 Make functor 261 274 285 make_formatter 253 make_image 344 make_lexer 259 make_matrix 241 map 242 270 Map module 273 380 map2 270 mapi 242 Marshal module 275 match_beginning 327 match_end 327 Match_failure exception 102 104 222 matched_group 327 matched_string 327 max 22
293. le Callback registering Caml values with the C runtime Module Gc memory management control and statistics finalised values Module Lexing the run time library for lexers generated by ocamllex 189 189 190 190 190 193 193 198 199 200 203 207 209 212 214 219 221 221 19 18 19 19 19 20 19 21 19 22 19 23 19 24 19 25 19 26 19 27 19 28 19 29 19 30 19 31 19 32 Module Marshal marshaling of data structures 2 0200 Module Nativeint processor native integers 0 0 00 002 2s Module Oo object oriented extension 2 a Module Parsing the run time library for parsers generated by ocamlyacc Module Printexc a catch all exception handler ooo a a Module Printf formatting printing functions oaoa e a a Module Queue first in first out queues oaoa ee Module Random pseudo random number generator osoo a Module Set sets over ordered types oaoa a Module Sort sorting and merging lists 2 aa a Module Stack last in first out stacks ooa ee Module Stream streams and parsers 2 ee a Module String string operations 2 2 ee Module Sys system interface 2 ee ee Module Weak arrays of weak pointers 2 2 ee ee 20 The unix library Unix system calls 20 1 Module Unix interface to the Unix system 0 00 000202005 21 The num library arbitrary precision rational arithmetic 21 1 21 2 Modul
294. lements have Caml type a representation kind b and memory layout c val create kind a b kind gt layout c layout gt dim int gt a b c t Arrayl create kind layout dim returns a new bigarray of one dimension whose size is dim kind and layout determine the array element kind and the array layout as described for Genarray create val dim a b c t gt int Return the size dimension of the given one dimensional big array external get a b c t gt int gt a Array1 get a x or alternatively a x returns the element of a at index x x must be greater or equal than 0 and strictly less than Array1 dim a if a has C layout If a has Fortran layout x must be greater or equal than 1 and less or equal than Array1 dim a Otherwise Invalid_arg is raised external set a b c t gt int gt a gt unit Array1 set a x v also written a x lt v stores the value v at index x in a x must be inside the bounds of a as described in Array1 get otherwise Invalid_arg is raised external sub a b c t gt pos int gt len int gt a b c t Extract a sub array of the given one dimensional big array See Genarray sub_left for more details external blit src a b c t gt dst a b c t gt unit Copy the first big array to the second big array See Genarray blit for more details external fill a b
295. les produced by the ocamlc command are self executable and manage to launch the ocamlrun command on themselves auto matically That is assuming caml out is a bytecode executable file caml out arg arg works exactly as ocamlrun caml out arg argy Notice that it is not possible to pass options to ocamlrun when invoking caml out directly 10 2 Options The following command line option is recognized by ocamlrun v When set the memory manager prints some verbose messages on standard error 147 148 The following environment variables are also consulted OCAMLRUNPARAM Set the garbage collection parameters If OCAMLRUNPARAM is not set CAMLRUNPARAM will be used instead This variable must be a sequence of parameter specifications A parameter specification is an option letter followed by an sign a decimal number and an optional multiplier There are seven options the first six correspond to the fields of the control record documented in section 19 9 s minor_heap_size Size of the minor heap i major_heap_increment Minimum size increment for the major heap o space_overhead The major GC speed setting O max_overhead The heap compaction trigger setting v verbose What GC messages to print to stderr This is a sum of values selected from the following 1 Start of major GC cycle 2 Minor collection and major GC slice 4 Growing and shrinking of the heap 8 Resizing of stacks and memory manager tables 1
296. lib lcurses On some machines you may need to put cclib ltermcap or cclib lcurses cclib ltermcap instead of cclib lcurses 17 7 Advanced topic callbacks from C to Caml So far we have described how to call C functions from Caml In this section we show how C functions can call Caml functions either as callbacks Caml calls C which calls Caml or because the main program is written in C 17 7 1 Applying Caml closures from C C functions can apply Caml functional values closures to Caml values The following functions are provided to perform the applications e callback f a applies the functional value f to the value a and return the value returned by f e callback2 f a b applies the functional value f which is assumed to be a curried Caml function with two arguments to a and b e callback3 f a b c applies the functional value f a curried Caml function with three arguments to a b and c e callbackN f n args applies the functional value fto the n arguments contained in the array of values args If the function f does not return but raises an exception that escapes the scope of the application then this exception is propagated to the next enclosing Caml code skipping over the C code That is if a Caml function f calls a C function g that calls back a Caml function h that raises a stray exception then the execution of g is interrupted and the exception is propagated back into f If the C code wishes
297. lied to self as in the following example the type of self is unified with the closed type c a closed object type is an object type without ellipsis This would constrains the type of self be closed and is thus rejected Indeed the type of self cannot be closed this would prevent any further extension of the class Therefore a type error is generated when the unification of this type with another type would result in a closed object type class c object self method m self c gt c end This expression has type lt m c gt but is here used with type c lt gt Self type cannot escape its class 50 This problem can sometimes be avoided by first defining the abbreviation using a class type class type c0 object method m cO end class type c0 object method m c0 end class c c0 object self method m self cO gt c0 end class c c0 It is also possible to use a virtual class Inheriting from this class simultaneously allows to enforce all methods of c to have the same type as the methods of cO class virtual c0 object method virtual m cO end class virtual c0 object method virtual m c0 end class c object self inherit cO method m self c0 gt c0 end class c object method m c0 end One could think of defining the type abbreviation directly type cl lt m c1 gt type cl lt m cl gt However the abbreviation cO cannot be defined directly in
298. line parameters Unlike caml_main this argv parameter is used only to initialize Sys argv but not for finding the name of the executable file The native code compiler ocamlopt also supports the output obj option causing it to output a C object file containing the native code for all Caml modules on the command line as well as the Caml startup code Initialization is performed by calling caml_startup as in the case of the bytecode compiler For the final linking phase in addition to the object file produced by output obj you will have to provide the Objective Caml runtime library libcamlrun a for bytecode libasmrun a for native code as well as all C libraries that are required by the Caml libraries used For instance assume the Caml part of your program uses the Unix library With ocamlc you should do ocamlc output obj o camlcode o unix cma other cmo and cma files cc o myprog C objects and libraries camlcode o L usr local lib ocaml lunix lcamlrun With ocamlopt you should do ocamlopt output obj o camlcode o unix cmxa other cmx and cmxa files cc o myprog C objects and libraries camlcode o L usr local lib ocaml lunix lasmrun Warning On some ports special options are required on the final linking phase that links to gether the object file produced by the output obj option and the remainder of the program Those options are shown in the configuration file config Makefile generated during compilation of Ob ject
299. ll tbl x returns the list of all data associated with x in tbl The current binding is returned first then the previous bindings in reverse order of introduction in the table mem a b t gt a gt bool Hashtbl mem tbl x checks if x is bound in tbl remove a b t gt a gt unit Hashtbl remove tbl x removes the current binding of x in tbl restoring the previous binding if it exists It does nothing if x is not bound in tbl iter f key a gt data b gt unit gt a b t gt unit Hashtbl iter f tbl applies f to all bindings in table tbl f receives the key as first argument and the associated value as second argument The order in which the bindings are passed to f is unspecified Each binding is presented exactly once to f Chapter 19 The standard library 261 Functorial interface module type HashedType sig type t val equal t gt t gt bool val hash t gt int end The input signature of the functor Hashtbl Make t is the type of keys equal is the equality predicate used to compare keys hash is a hashing function on keys returning a non negative integer It must be such that if two keys are equal according to equal then they must have identical hash values as computed by hash Examples suitable equal hash pairs for arbitrary key types include Hashtbl hash for comparing objects by structure and Hashtbl hash for comparing objects by addresses e g for
300. long my_c_array 100 200 extern float my_fortran_array_ 300 400 value caml_get_c_array value unit long dims 2 dims 0 100 dims 1 200 return alloc_bigarray BIGARRAY_NATIVEINT BIGARRAY_C_LAYOUT 2 my_c_array dims value caml_get_fortran_array value unit return alloc_bigarray_dims BIGARRAY_FLOAT32 BIGARRAY_FORTRAN_LAYOUT 2 my_fortran_array_ 300L 400L 372 Part V Appendix 373 INDEX TO THE LIBRARY Index to the library operator 236 operator 224 amp operator 225 amp amp operator 225 operator 225 operator 227 operator 320 operator 227 operator 320 operator 225 operator 227 operator 320 operator 225 operator 227 operator 320 operator 225 operator 227 operator 320 operator 236 lt operator 224 lt operator 321 lt operator 224 lt operator 321 lt gt operator 224 lt gt operator 321 operator 224 operator 321 operator 224 gt operator 224 gt operator 321 gt operator 224 gt operator 321 operator 230 operator 228 operator 225 operator 225 operator 227 abs 226 263 265 277 abs_float 228 abs_num 321 accept 311 338 375 access 302 acos 227 add 260 262 265 277 282 348 add_available_units 350 add_buffer 244 add_channel 244 add_char 243 add_
301. losure v string_length v returns the length number of characters of the string v Byte v n returns the nt character of the string v with type char Characters are num bered from 0 to string_length v 1 Byte_u v n returns the n character of the string v with type unsigned char Characters are numbered from 0 to string_length v 1 String_val v returns a pointer to the first byte of the string v with type char This pointer is a valid C string there is a null character after the last character in the string However Caml strings can contain embedded null characters that will confuse the usual C functions over strings Double_val v returns the floating point number contained in value v with type double Double_field v n returns the nt element of the array of floating point numbers v a block tagged Double_array_tag Store_double_field v n d stores the double precision floating point number d in the nt element of the array of floating point numbers v Data_custom_val v returns a pointer to the data part of the custom block v This pointer has type void and must be cast to the type of the data contained in the custom block 202 Int32_val v returns the 32 bit integer contained in the int32 v Int64_val v returns the 64 bit integer contained in the int64 v Nativeint_val v returns the long integer contained in the nativeint v The expressions Field v n Byte v n and Byte_u v n are valid l
302. ls exception Break Exception raised on interactive interrupt if catch_break is on Chapter 19 The standard library 293 val catch_break bool gt unit catch_break governs whether interactive interrupt ctrl C terminates the program or raises the Break exception Call catch_break true to enable raising Break and catch_break false to let the system terminate the program on user interrupt 19 32 Module Weak arrays of weak pointers type a t The type of arrays of weak pointers weak arrays A weak pointer is an object that the garbage collector may erase at any time A weak pointer is said to be full if it points to an object empty if the object was erased by the GC val create int gt a t Weak create n returns a new weak array of length n All the pointers are initially empty val length a t gt int Weak length ar returns the length number of elements of ar val set a t gt int gt a option gt unit Weak set ar n Some el sets the nth cell of ar to be a full pointer to el Weak set ar n None sets the nth cell of ar to empty Raise Invalid_argument Weak set if n is not in the range 0 to Weak length a 1 val get a t gt int gt a option Weak get ar nreturns None if the nth cell of ar is empty Some x where x is the object if it is full Raise Invalid_argument Weak get ifn is not in the range 0 to Weak length a 1 val check a t gt int gt bool
303. lue name operator name cconstr name ncconstr name label name tag name typeconstr name field name module name modtype name class name inst var name method name lowercase ident operator name prefix symbol infix symbol or amp capitalized ident false true capitalized ident lowercase ident capitalized ident lowercase ident lowercase ident capitalized ident ident lowercase ident lowercase ident lowercase ident As shown above prefix and infix symbols as well as some keywords can be used as value names ee provided they are written between parentheses Keywords such as and false are also constructor names The capitalization rules are summarized in the table below 92 Name space Case of first letter Values lowercase Constructors uppercase Labels lowercase Variant tag uppercase Type constructors lowercase Record fields lowercase Classes lowercase Methods lowercase Modules uppercase Module types any Referring to named objects value path value name module path lowercase ident cconstr cconstr name module path capitalized ident ncconstr mncconstr name module path capitalized ident typeconstr typeconstr name extended module path lowercase ident field field name module path lowercase ident module path module name module path capitalized ident extended module path module n
304. m identifiers let keyword_table Hashtbl create 53 let _ List iter fun kwd tok gt Hashtbl add keyword_table kwd tok keywordi KWD1 keyword2 KWD2 keyword100 KWD100 rule token parse ASZ aer PA aA gg ra T oe let id Lexing lexeme lexbuf in try Hashtbl find keyword_table s with Not_found gt IDENT s 166 Chapter 13 Dependency generator ocamldep The ocamldep command scans a set of Objective Caml source files m1 and m1i files for references to external compilation units and outputs dependency lines in a format suitable for the make utility This ensures that make will compile the source files in the correct order and recompile those files that need to when a source file is modified The typical usage is ocamldep options mli ml gt depend where mli ml expands to all source files in the current directory and depend is the file that should contain the dependencies See below for a typical Makefile Dependencies are generated both for compiling with the bytecode compiler ocamlc and with the native code compiler ocamlopt 13 1 Options The following command line option is recognized by ocamldep I directory Add the given directory to the list of directories searched for source files If a source file foo ml mentions an external compilation unit Bar a dependency on that unit s interface bar cmi is generated only if the source for bar is found in the current directory or i
305. m_delete firstkey t gt string nextkey t gt string Enumerate all keys in the given database in an unspecified order firstkey db returns the first key and repeated calls to nextkey db return the remaining keys Not_found is raised when all keys have been enumerated iter f key string gt data string gt a gt t gt unit iter f db applies f to each key data pair in the database db f receives key as first argument and data as second argument Chapter 26 The dynlink library dynamic loading and linking of object files The dynlink library supports type safe dynamic loading and linking of bytecode object files cmo and cma files in a running bytecode program Type safety is ensured by limiting the set of modules from the running program that the loaded object file can access and checking that the running program and the loaded object file have been compiled against the same interfaces for these modules Programs that use the dynlink library simply need to link dynlink cma with their object files and other libraries Dynamic linking is available only to bytecode programs compiled with ocam1c not to native code programs compiled with ocamlopt 26 1 Module Dynlink dynamic loading of bytecode object files val init unit gt unit Initialize the library Must be called before loadfile val loadfile string gt unit Load the given bytecode object file and link it All toplevel expressions in the loade
306. mandatory for start symbols only Other nonterminal symbols need not be given types by hand these types will be inferred when running the output files through the Objective Caml compiler unless the s option is in effect The type part is an arbitrary Caml type expression except that all type constructor names must be fully qualified as explained above for token left symbol symbol right symbol symbol nonassoc symbol symbol Associate precedences and associativities to the given symbols All symbols on the same line are given the same precedence They have higher precedence than symbols declared before in a Zleft 4right or Znonassoc line They have lower precedence than symbols declared 162 after in a Zleft right or nonassoc line The symbols are declared to associate to the left Aleft to the right Aright or to be non associative nonassoc The symbols are usually tokens They can also be dummy nonterminals for use with the prec directive inside the rules 12 4 3 Rules The syntax for rules is as usual nonterminal symbol symbol semantic action eee symbol symbol semantic action Rules can also contain the Zprec symbol directive in the right hand side part to override the default precedence and associativity of the rule with the precedence and associativity of the given symbol Semantic actions are arbitrary Caml expressions that are evaluated to produce the semantic attribute att
307. me exists remove string gt unit Remove the given file name from the file system rename src string gt dst string gt unit Rename a file The first argument is the old name and the second is the new name getenv string gt string Return the value associated to a variable in the process environment Raise Not_found if the variable is unbound command string gt int Execute the given shell command and return its exit code time unit gt float Return the processor time in seconds used by the program since the beginning of execution chdir string gt unit Change the current working directory of the process getcwd unit gt string Return the current working directory of the process interactive bool ref This reference is initially set to false in standalone programs and to true if the code is being executed under the interactive toplevel system ocam1 os_type string Operating system currently executing the Caml program One of Unix Win32 or MacOS word_size int Size of one word on the machine currently executing the Caml program in bits 32 or 64 max_string_length int Maximum length of a string max_array_length int Maximum length of an array 292 Signal handling type signal_behavior val val val val val val val val val val val val val val val val val val val val val val val Signal_default Signal_ignore Signal_handle of int gt unit Wha
308. mit the depth of printing to 1 Useful to browse large data structures without printing them in full display can be abbreviated as d When printing a complex expression a name of the form integer is automatically assigned to its value Such names are also assigned to parts of the value that cannot be printed because the maximal printing depth is exceeded Named values can be printed later on with the commands p integer or d integer Named values are valid only as long as the program is stopped They are forgotten as soon as the program resumes execution set print_depth d Limit the printing of values to a maximal depth of d set print_length Limit the printing of values to at most l nodes printed 15 8 Controlling the debugger 15 8 1 Setting the program name and arguments set program file Set the program name to file set arguments arguments Give arguments as command line arguments for the program A shell is used to pass the arguments to the debugged program You can therefore use wildcards shell variables and file redirections inside the arguments To debug programs that read from standard input it is recommended to redirect their input from a file using set arguments lt input file otherwise input to the program and input to the debugger are not properly separated and inputs are not properly replayed when running the program backwards 15 8 2 How programs are loaded The loadingmode variable controls how the program is
309. module Chapter 4 The module system This chapter introduces the module system of Objective Caml 4 1 Structures A primary motivation for modules is to package together related definitions such as the definitions of a data type and associated operations over that type and enforce a consistent naming scheme for these definitions This avoids running out of names or accidentally confusing names Such a package is called a structure and is introduced by the struct end construct which contains an arbitrary sequence of definitions The structure is usually given a name with the module binding Here is for instance a structure packaging together a type of priority queues and their operations module PrioQueue struct type priority int type a queue Empty Node of priority a a queue a queue let empty Empty let rec insert queue prio elt match queue with Empty gt Node prio elt Empty Empty Node p e left right gt if prio lt p then Node prio elt insert right p e left else Node p e insert right prio elt left exception Queue_is_empty let rec remove_top function Empty gt raise Queue_is_empty Node prio elt left Empty gt left Node prio elt Empty right gt right Node prio elt Node lprio lelt _ _ as left Node rprio relt _ _ as right gt if lprio lt rprio then Node lprio lelt remove_top left right
310. mplementation definition Compilation units bridge the module system and the separate compilation system A compila tion unit is composed of two parts an interface and an implementation The interface contains a sequence of specifications just as the inside of a sig end signature expression The implemen tation contains a sequence of definitions just as the inside of a struct end module expression A compilation unit also has a name unit name derived from the names of the files containing the interface and the implementation see chapter 8 for more details A compilation unit behaves roughly as the module definition module unit name sig unit interface end struct unit implementation end A compilation unit can refer to other compilation units by their names as if they were regular modules For instance if U is a compilation unit that defines a type t other compilation units can refer to that type under the name U t they can also refer to U as a whole structure Except for names of other compilation units a unit interface or unit implementation must not have any other free variables In other terms the type checking and compilation of an interface or implementation proceeds in the initial environment name sig interface end name sig interface end where name namey are the names of the other compilation units available in the search path see chapter 8 for more details and interface interface are their
311. n By default integer literals are in decimal radix 10 The following prefixes select a different radix Prefix Radix Ox OX hexadecimal radix 16 Oo 00 octal radix 8 Ob OB binary radix 2 The initial O is the digit zero the O for octal is the letter O The interpretation of integer literals that fall outside the range of representable integer values is undefined Floating point literals float literal 0 9 7 0 9 e E 0 9 7 Floating point decimals consist in an integer part a decimal part and an exponent part The integer part is a sequence of one or more digits optionally preceded by a minus sign The decimal part is a decimal point followed by zero one or more digits The exponent part is the character e or E followed by an optional or sign followed by one or more digits The decimal part or the exponent part can be omitted but not both to avoid ambiguity with integer literals The interpretation of floating point literals that fall outside the range of representable floating point values is undefined Character literals regular char NGP alt b r 0 9 0 9 0 9 char literal Chapter 6 The Objective Caml language 87 Character literals are delimited by single quote characters The two single quotes enclose either one character different from and or one of the escape sequences below Sequence Char
312. n code this library supports two different memory layouts for big arrays one compatible with the C conventions the other compatible with the Fortran conventions In the C style layout array indices start at 0 and multi dimensional arrays are laid out in row major format That is for a two dimensional array all elements of row 0 are contiguous in memory followed by all elements of row 1 etc In other terms the array elements at x y and x y 1 are adjacent in memory In the Fortran style layout array indices start at 1 and multi dimensional arrays are laid out in column major format That is for a two dimensional array all elements of column 0 are contiguous in memory followed by all elements of column 1 etc In other terms the array elements at x y and x 1 y are adjacent in memory 360 Each layout style is identified at the type level by the abstract types c_layout and fortran_layout respectively type a layout The type a layout represents one of the two supported memory layouts C style if a is c_layout Fortran style if a is fortran_layout val c_layout c_layout layout val fortran_layout fortran_layout layout The abstract values c_layout and fortran_layout represent the two supported layouts at the level of values Generic arrays of arbitrarily many dimensions module Genarray sig type Ca b c t The type Genarray t is the type of big arrays with variable numbers of dimensions Any
313. n expr belongs to the class of syntactic values which includes constants identifiers functions tuples of syntactic values etc In all other cases for instance expr is a function application a polymorphic mutable could have been created and generalization is therefore turned off Non generalized type variables in a type cause no difficulties inside a given structure or compilation unit the contents of a ml file or an interactive session but they cannot be allowed inside signatures nor in compiled interfaces cmi file because they could be used inconsistently later Therefore the compiler flags an error when a structure or compilation unit defines a value name whose type contains non generalized type variables There are two ways to fix this error e Adda type constraint or a m1i file to give a monomorphic type without type variables to name For instance instead of writing let sort_int_list Sort list lt inferred type a list gt a list with a not generalized write let sort_int_list Sort list lt int list gt int list e If you really need name to have a polymorphic type turn its defining expression into a function by adding an extra parameter For instance instead of writing let map_length List map Array length inferred type a array list gt int list with a not generalized write let map_length lv List map Array length lv Reference to undefined global mod
314. n one of the directories specified with I Otherwise Bar is assumed to be a module form the standard library and no dependencies are generated For programs that span multiple directories it is recommended to pass ocamldep the same I options that are passed to the compiler native Generate dependencies for a pure native code program no bytecode version When an implementation file m1 file has no explicit interface file mli file ocamldep generates dependencies on the bytecode compiled file cmo file to reflect interface changes This can cause unnecessary bytecode recompilations for programs that are compiled to native code only The flag native causes dependencies on native compiled files cmx to be generated instead of on cmo files This flag makes no difference if all source files have explicit mli interface files 167 168 13 2 A typical Makefile Here is a template Makefile for a Objective Caml program OCAMLC ocamlc OCAMLOPT ocamlopt OCAMLDEP ocamldep INCLUDES all relevant I options here OCAMLFLAGS INCLUDES add other options for ocamlc here OCAMLOPTFLAGS INCLUDES add other options for ocamlopt here progi should be compiled to bytecode and is composed of three units modi mod2 and mod3 The list of object files for progi PROG1_OBJS mod1 cmo mod2 cmo mod3 cmo progi PROG1_OBJS OCAMLC o prog1 OCAMLFLAGS PROG1_OBJS prog2 should be compiled to native code an
315. n option to the C compiler and linker when linking in custom runtime mode See the corresponding option for ocamlc in chapter 8 custom Link in custom runtime mode See the corresponding option for ocamlc in chapter 8 Chapter 9 The toplevel system ocaml 145 I directory Add the given directory to the list of directories searched for compiled object code files cmo and cma o exec file Specify the name of the toplevel file produced by the linker The default is a out 146 Chapter 10 The runtime system ocamlrun The ocamlrun command executes bytecode files produced by the linking phase of the ocamlc command 10 1 Overview The ocamlrun command comprises three main parts the bytecode interpreter that actually ex ecutes bytecode files the memory allocator and garbage collector and a set of C functions that implement primitive operations such as input output The usage for ocamlrun is ocamlrun options bytecode executable arg argn The first non option argument is taken to be the name of the file containing the executable bytecode That file is searched in the executable path as well as in the current directory The remaining arguments are passed to the Caml Light program in the string array Sys argv Element 0 of this array is the name of the bytecode executable file elements 1 to n are the remaining arguments arg to arg As mentioned in chapter 8 in most cases the bytecode executable fi
316. names name The cmi and cmo files produced by the compiler have the same base name as the source file Hence the compiled files always have their base name equal modulo capitalization of the first letter to the name of the module they describe for cmi files or implement for cmo files When the compiler encounters a reference to a free module identifier Mod it looks in the search path for a file mod cmi note lowercasing of first letter and loads the compiled interface contained in that file As a consequence renaming cmi files is not advised the name of a cmi file must 136 always correspond to the name of the compilation unit it implements It is admissible to move them to another directory if their base name is preserved and the correct I options are given to the compiler The compiler will flag an error if it loads a cmi file that has been renamed Compiled bytecode files cmo files on the other hand can be freely renamed once created That s because the linker never attempts to find by itself the cmo file that implements a module with a given name it relies instead on the user providing the list of cmo files by hand 8 4 Common errors This section describes and explains the most frequently encountered error messages Cannot find file filename The named file could not be found in the current directory nor in the directories of the search path The filename is either a compiled interface file cmi file or
317. nation chunks overlap Raise Invalid_argument Array blit if o1 and len do not designate a valid subarray of v1 or if o2 and len do not designate a valid subarray of v2 242 val val val val val val val val to_list a array gt a list Array to_list a returns the list of all the elements of a of_list a list gt a array Array of_list 1 returns a fresh array containing the elements of 1 iter f a gt unit gt a array gt unit Array iter f a applies function f in turn to all the elements of a It is equivalent to f a 0 f a 1 f a Array length a 1 map f a gt b gt a array gt b array Array map f a applies function f to all the elements of a and builds an array with the results returned by f f a 0 f a 1 f a Array length a 1 iteri f int gt a gt unit gt a array gt unit mapi f int gt a gt b gt a array gt b array Same as Array iter and Array map respectively but the function is applied to the index of the element as first argument and the element itself as second argument fold_left f a gt b gt a gt init a gt b array gt a Array fold_left f x a computes f x a 0 a 1 a m 1 where n is the length of the array a fold_right f b gt a gt a gt b array gt init a gt a Array fold_right
318. nd remove it from the stream Raise Stream Failure if the stream is empty val empty a t gt unit Return if the stream is empty else raise Stream Failure Useful functions val peek a t gt a option Return Some of the first element of the stream or None if the stream is empty val junk a t gt unit Remove the first element of the stream possibly unfreezing it before val count a t gt int Return the current count of the stream elements i e the number of the stream elements discarded val npeek int gt a t gt a list npeek n returns the list of the n first elements of the stream or all its remaining elements if less than n elements are available 19 30 Module String string operations val length string gt int Return the length number of characters of the given string val get string gt int gt char String get s n returns character number n in string s The first character is character number 0 The last character is character number String length s 1 Raise Invalid_argument if n is outside the range 0 to String length s 1 You can also write s n instead of String get s n Chapter 19 The standard library 289 val val val val val val val val val set string gt int gt char gt unit String set s n c modifies string s in place replacing the character number n by c Raise Invalid_argument if n is outside the
319. nd to the lexer buffer passed to the parsing function val lexeme lexbuf gt string Lexing lexeme lexbuf returns the string matched by the regular expression Chapter 19 The standard library 269 val lexeme_char lexbuf gt int gt char Lexing lexeme_char lexbuf i returns character number i in the matched string val lexeme_start lexbuf gt int Lexing lexeme_start lexbuf returns the position in the input stream of the first character of the matched string The first character of the stream has position 0 val lexeme_end lexbuf gt int Lexing lexeme_end lexbuf returns the position in the input stream of the character following the last character of the matched string The first character of the stream has position 0 19 16 Module List list operations Some functions are flagged as not tail recursive A tail recursive function uses constant stack space while a non tail recursive function uses stack space proportional to the length of its list argument which can be a problem with very long lists When the function takes several list arguments an approximate formula giving stack usage in some unspecified constant unit is shown in parentheses The above considerations can usually be ignored if your lists are not longer than about 10000 elements val length a list gt int Return the length number of elements of the given list val hd a list gt a Return the first element of the given list Raise
320. ndard output val print_float float gt unit Print a floating point number in decimal on standard output val print_endline string gt unit Print a string followed by a newline character on standard output val print_newline unit gt unit Print a newline character on standard output and flush standard output This can be used to simulate line buffering of standard output Chapter 18 The core library 231 Output functions on standard error val prerr_char char gt unit Print a character on standard error val prerr_string string gt unit Print a string on standard error val prerr_int int gt unit Print an integer in decimal on standard error val prerr_float float gt unit Print a floating point number in decimal on standard error val prerr_endline string gt unit Print a string followed by a newline character on standard error and flush standard error val prerr_newline unit gt unit Print a newline character on standard error and flush standard error Input functions on standard input val read_line unit gt string Flush standard output then read characters from standard input until a newline character is encountered Return the string of all characters read without the newline character at the end val read_int unit gt int Flush standard output then read one line from standard input and convert it to an integer Raise Failure int_of_string if the line read is n
321. ned by get_ellipsis_text Nothing happens if max is not greater than 1 val get_max_boxes unit gt int Return the maximum number of boxes allowed before ellipsis val over_max_boxes unit gt bool Test the maximum number of boxes allowed have already been opened 250 Advanced formatting val open_hbox unit gt unit open_hbox opens a new pretty printing box This box is horizontal the line is not split in this box new lines may still occur inside boxes nested deeper val open_vbox int gt unit open_vbox d opens a new pretty printing box with offset d This box is vertical every break hint inside this box leads to a new line When a new line is printed in the box d is added to the current indentation val open_hvbox int gt unit open_hvbox d opens a new pretty printing box with offset d This box is horizontal vertical it behaves as an horizontal box if it fits on a single line otherwise it behaves as a vertical box When a new line is printed in the box d is added to the current indentation val open_hovbox int gt unit open_hovbox d opens a new pretty printing box with offset d This box is horizontal or vertical break hints inside this box may lead to a new line if there is no more room on the line to print the remainder of the box When a new line is printed in the box d is added to the current indentation Tabulations val open_tbox uni
322. ng a fully explicit coercion Chapter 3 Objects in Caml 49 function x gt x c gt c c gt c lt fun gt Thus one can define class c as follows class c object self inherit c method m self c gt c method m 1 end class c object method m c method m int end An alternative is to define class c this way of course this definition is not equivalent to the previous one class virtual c object _ a method virtual m a end class virtual c object a method virtual m a end Then a coercion operator is not even required class c object self inherit c method m self method m 1 end class c object a method m a method m int end Here the simple coercion operator e gt c can be used to coerce an object expression e from type c to type c Semi implicit coercions are actually defined so as to work correctly with classes returning self mew c gt c c lt obj gt Another common problem may occur when one tries to define a coercion to a class c inside the definition of class c The problem is due to the type abbreviation not being completely defined yet and so its subtypes are not clearly known Then a coercion _ c gt c is taken to be the identity function as in function x gt x gt a a gt a lt fun gt As a consequence if the coercion is app
323. ng of x to y If x was already bound in m its previous binding disappears val find key gt at gt a find x mreturns the current binding of x in m or raises Not_found if no such binding exists val remove key gt at gt at remove x mreturns a map containing the same bindings as m except for x which is unbound in the returned map val mem key gt a t gt bool mem x m returns true if m contains a binding for m and false otherwise val iter f key key gt data a gt unit gt a t gt unit iter f m applies f to all bindings in map m f receives the key as first argument and the associated value as second argument The order in which the bindings are passed to f is unspecified Only current bindings are presented to f bindings hidden by more recent bindings are not passed to f val map f a gt b gt at gt bt map f mreturns a map with same domain as m where the associated value a of all bindings of m has been replaced by the result of the application of f to a The order in which the associated values are passed to f is unspecified val mapi f key gt a gt b gt at gt bt Same as map but the function receives as arguments both the key and the associated value for each binding of the map val fold f key key gt data a gt b gt b gt a t gt init b gt b fold f m a computes f kN dN f ki di a where k1 KN are the
324. ng proceeds in two steps first a pattern is selected by matching the stream against the first components of the stream patterns then the following components of the selected pattern are checked against the stream If the following components do not match the exception Stream Error is raised There is no backtracking here stream matching commits to the pattern selected according to the first element If none of the first components of the stream patterns match the exception Stream Failure is raised The Stream Failure exception causes the next alternative to be tried if it occurs during the matching of the first element of a stream before matching has committed to one pattern The streams hold the count of their elements discarded The optional pattern before the first stream pattern is bound to the stream count before the matching The one after each stream pattern optional too is bound to the stream count after the matching The exception Stream Error has a string parameter coming from the optional expr after the stream pattern components its default is the empty string This expression is evaluated only in case of error See Functional programming using Caml Light for a more gentle introductions to streams and for some examples of their use in writing parsers A more formal presentation of streams and a discussion of alternate semantics can be found in Parsers in ML by Michel Mauny and Daniel de Rauglaudre in the proceedings of the 1
325. nitialized the initial values of array elements is unspecified Genarray create raises Invalid_arg if the number of dimensions is not in the range 1 to 16 inclusive or if one of the dimensions is negative Chapter 28 The bigarray library 361 external num_dims a b c t gt int Return the number of dimensions of the given big array external nth_dim a b c t gt int gt int Genarray nth_dim a n returns the n th dimension of the big array a The first dimension corresponds to n 0 the second dimension corresponds to n 1 the last dimension to n Genarray num_dims a 1 Raise Invalid_arg if n is less than 0 or greater or equal than Genarray num_dims a external get a b c t gt int array gt a g y Read an element of a generic big array Genarray get a li1 iN returns the element of a whose coordinates are i1 in the first dimension i2 in the second dimension iN in the N th dimension If a has C layout the coordinates must be greater or equal than 0 and strictly less than the corresponding dimensions of a If a has Fortran layout the coordinates must be greater or equal than 1 and less or equal than the corresponding dimensions of a Raise Invalid_arg if the array a does not have exactly N dimensions or if the coordinates are outside the array bounds If N gt 3 alternate syntax is provided you can write a il i2 iN instead of Genarray get a il iN
326. ns below for output to standard error It is defined as formatter_of_out_channel stderr formatter_of_buffer Buffer t gt formatter formatter_of_buffer b returns a new formatter writing to buffer b As usual the formatter has to be flushed at the end of pretty printing using pp_print_flush or pp_print_newline to display all the pending material In this case the buffer is also flushed using Buffer flush stdbuf Buffer t The string buffer in which str_formatter writes str_formatter formatter A formatter to use with formatting functions below for output to the stdbuf string buffer Chapter 19 The standard library 253 val val val val val val val val val val val val val val val val val val val val val val val val val val val val val val val val val val val val flush_str_formatter unit gt string Returns the material printed with str_formatter flushes the formatter and reset the corresponding buffer str_formatter is defined as formatter_of_buffer stdbuf make_formatter out buf string gt pos int gt len int gt unit gt flush unit gt unit gt formatter make_formatter out flush returns a new formatter that writes according to the output function out and the flushing function flush Hence a formatter to out channel oc is returned by make_formatter output oc fun gt flush oc pp_open_hbox formatter gt unit gt unit pp_open_vbox fo
327. nt Tag3 gt Tag3 val f K Tagi of int Tag2 of bool Tag3 gt string lt fun gt or combined with with aliases let gi function Tagl _ gt Tagi Tag2 _ gt Tag2 val g1 x Tagi of a Tag2 of b gt string lt fun gt let g function myvariant as x gt gi x Tag3 gt Tag3 val g K Tagi of int Tag2 of bool Tag3 gt string lt fun gt 34 Chapter 3 Objects in Caml Chapter written by J r me Vouillon and Didier R my This chapter gives an overview of the object oriented features of Objective Caml 3 1 Classes and objects The class point has one instance variable x and two methods get_x and move The initial value of the instance variable is 0 The variable x is declared mutable so the method move can change its value class point object val mutable x 0 method get_x x method move d x lt x d end class point object val mutable x int method get_x int method move int gt unit end H H H H We now create a new point p let p new point val p point lt obj gt Note that the type of p is point This is an abbreviation automatically defined by the class definition above It stands for the object type lt get_x int move int gt unit gt listing the methods of class point along with their types Let us apply some methods to p p get_x int 0 p move
328. nt64 Return the absolute value of its argument max_int int64 The greatest representable 64 bit integer 263 1 min_int int64 The smallest representable 64 bit integer 2 logand int64 gt int64 gt int64 Bitwise logical and 266 val val val val val val val val val val val logor int64 gt int64 gt int64 Bitwise logical or logxor int64 gt int64 gt int64 Bitwise logical exclusive or lognot int64 gt int64 Bitwise logical negation shift_left int64 gt int gt int64 Int64 shift_left x y shifts x to the left by y bits shift_right int64 gt int gt int64 Int64 shift_right x y shifts x to the right by y bits This is an arithmetic shift the sign bit of x is replicated and inserted in the vacated bits shift_right_logical int64 gt int gt int64 Int64 shift_right_logical x y shifts x to the right by y bits This is a logical shift zeroes are inserted in the vacated bits regardless of the sign of x of_int int gt int64 Convert the given integer type int to a 64 bit integer type int64 to_int int64 gt int Convert the given 64 bit integer type int64 to an integer type int On 64 bit platforms the 64 bit integer is taken modulo 263 i e the high order bit is lost during the conversion On 32 bit platforms the 64 bit integer is taken modulo 2 i e the top 33 bits are lost during the conversion of_float float g
329. o For the most frequently used commands ambiguous abbreviations are allowed For instance r stands for run even though there are others commands starting with r You can test the validity of an abbreviation using the help command If the previous command has been successful a blank line typing just RET will repeat it 15 3 1 Getting help The Objective Caml debugger has a simple on line help system which gives a brief description of each command and variable Chapter 15 The debugger ocamldebug 177 help Print the list of commands help command Give help about the command command help set variable help show variable Give help about the variable variable The list of all debugger variables can be obtained with help set help info topic Give help about topic Use help info to get a list of known topics 15 3 2 Accessing the debugger state set variable value Set the debugger variable variable to the value value show variable Print the value of the debugger variable variable info subject Give information about the given subject For instance info breakpoints will print the list of all breakpoints 15 4 Executing a program 15 4 1 Events Events are interesting locations in the source code corresponding to the beginning or end of evaluation of interesting sub expressions Events are the unit of single stepping stepping goes to the next or previous event encountered in the program execution Also b
330. o allocate before the fields can receive their final value first initialize with a constant value e g Val_unit then allocate then modify the fields with the correct value see rule 6 Rule 6 Direct assignment to a field of a block as in 206 Field v n w is safe only if v is a block newly allocated by alloc_small that is if no allocation took place between the allocation of v and the assignment to the field In all other cases never assign directly If the block has just been allocated by alloc_shr use initialize to assign a value to a field for the first time initialize kField v n w Otherwise you are updating a field that previously contained a well formed value then call the modify function modify amp Field v n w To illustrate the rules above here is a C function that builds and returns a list containing the two integers given as parameters First we write it using the simplified allocation functions value alloc_list_int int i1 int i2 CAMLparam0 CAMLlocal2 result r r alloc 2 0 Allocate a cons cell Store_field r 0 Val_int i2 car the integer i2 Store_field r 1 Val_int 0 cdr the empty list result alloc 2 0 Allocate the other cons cell Store_field result 0 Val_int il car the integer i1 Store_field result 1 r cdr the first cons cell CAMLreturn result Here the registering of result is not strictly need
331. o be libraries of object code Such a library packs in two files lib cmxa and lib a a set of object files cmx o files Libraries are build with ocamlopt a see the description of the a option below The object files contained in the library are linked as regular cmx files see above in the order specified when the library was built The only difference is that if an object file contained in a library is not referenced anywhere in the program then it is not linked in Arguments ending in c are passed to the C compiler which generates a o object file This object file is linked with the program Arguments ending in o or a are assumed to be C object files and libraries They are linked with the program The output of the linking phase is a regular Unix executable file It does not need ocamlrun to run 11 2 Options The following command line options are recognized by ocamlopt a Build a library cmxa a file with the object files cmx o files given on the command line instead of linking them into an executable file The name of the library can be set with the o option The default name is library cmxa If cclib or ccopt options are passed on the command line these options are stored in the resulting cmxa library Then linking with this library automatically adds back the cclib and ccopt options as if they had been provided on the command line unless the noautolink option is given Compile only Suppress
332. o each func tion There is currently no way to perform time profiling on bytecode programs generated by ocamlc Native code programs generated by ocamlopt can be profiled for time and execution counts using the p option and the standard Unix profiler gprof Just add the p option when compiling and linking the program ocamlopt o myprog p other options files myprog gprof myprog Caml function names in the output of gprof have the following format Module name_function name_unique number Chapter 16 Profiling ocamlprof 191 Other functions shown are either parts of the Caml run time system or external C functions linked with the program The output of gprof is described in the Unix manual page for gprof 1 It generally consists of two parts a flat profile showing the time spent in each function and the number of invocation of each function and a hierarchical profile based on the call graph Currently only the Intel x86 Linux and Alpha Digital Unix ports of ocamlopt support the two profiles On other platforms gprof will report only the flat profile with just time information When reading the output of gprof keep in mind that the accumulated times computed by gprof are based on heuristics and may not be exact 192 Chapter 17 Interfacing C with Objective Caml This chapter describes how user defined primitives written in C can be linked with Caml code and called from Caml functions 17 1 Overview an
333. object is constructed It is also possible to evaluate an expression immediately after the object has been built Such code is written as an anonymous hidden method called an initializer Therefore is can access self and the instance variables Chapter 3 Objects in Caml 39 class printable_point x_init let origin x_init 10 10 in object self val mutable x origin method get_x x method move d x lt x d method print print_int self get_x initializer print_string new point at self print print_newline end class printable_point int gt object val mutable x int method get_x int method move int gt unit method print unit end let p new printable_point 17 new point at 10 val p printable_point lt obj gt Initializers cannot be overridden On the contrary all initializers are evaluated sequentially Ini tializers are particularly useful to enforce invariants Another example can be seen in section 5 1 3 4 Virtual methods It is possible to declare a method without actually defining it using the keyword virtual This method will be provided latter in subclasses A class containing virtual methods must be flagged virtual and cannot be instantiated that is no object of this class can be created It still defines abbreviations treating virtual methods as other methods class virtual abstract_point x_init object self val mutable x x_init method vir
334. ock_1 Read an array of 1 byte quantities deserialize_block_2 Read an array of 2 byte quantities deserialize_block_4 Read an array of 4 byte quantities deserialize_block_8 Read an array of 8 byte quantities deserialize_error Signal an error during deserialization input_value or Marshal from_ raise a Failure exception after cleaning up their internal data structures Serialization functions are attached to the custom blocks to which they apply Obviously dese rialization functions cannot be attached this way since the custom block does not exist yet when deserialization begins Thus the struct custom_operations that contain deserialization functions must be registered with the deserializer in advance using the register_custom_operations func tion declared in lt cam1 custom h gt Deserialization proceeds by reading the identifier off the input stream allocating a custom block of the size specified in the input stream searching the registered struct custom_operation blocks for one with the same identifier and calling its deserialize function to fill the custom block 17 9 5 Choosing identifiers Identifiers in struct custom_operations must be chosen carefully since they must identify uniquely the data structure for serialization and deserialization operations In particular con sider including a version number in the identifier this way the format of the data can be changed later yet backward compatible deserialisat
335. oes not contain Marshal Closures marshaling fails when it encounters a functional value inside v only pure data structures containing neither functions nor objects can safely be transmitted between different programs If flags contains Marshal Closures functional values will be marshaled as a position in the code of the program In this case the output of marshaling can only be read back in processes that run exactly the same program with exactly the same compiled code This is checked at 276 val val val val val val val un marshaling time using an MD5 digest of the code transmitted along with the code position to_string a gt mode extern_flags list gt string Marshal to_string v flags returns a string containing the representation of v as a sequence of bytes The flags argument has the same meaning as for Marshal to_channel to_buffer string gt pos int gt len int gt a gt mode extern_flags list gt int Marshal to_buffer buff ofs len v flags marshals the value v storing its byte representation in the string buff starting at character number ofs and writing at most len characters It returns the number of characters actually written to the string If the byte representation of v does not fit in len characters the exception Failure is raised from_channel in_channel gt a Marshal from_channel chan reads from channel chan the byte representation of a structured value as prod
336. omatically reclaimed by the garbage collector This requires some cooperation from C code that manipulates heap allocated blocks 17 5 1 Simple interface All the macros described in this section are declared in the memory h header file 204 Rule 1 A function that has parameters or local variables of type value must begin with a call to one of the CAMLparam macros and return with CAMLreturn or CAMLreturn0 There are six CAMLparam macros CAMLparamO to CAMLparam5 which take zero to five arguments respectively If your function has fewer than 5 parameters of type value use the corresponding macros with these parameters as arguments If your function has more than 5 parameters of type value use CAMLparam5 with five of these parameters and use one or more calls to the CAMLxparam macros for the remaining parameters CAMLxparamO to CAMLxparam5 The macros CAMLreturn and CAMLreturnO are used to replace the C keyword return Every occurence of return x must be replaced by CAMLreturn x every occurence of return without argument must be replaced by CAMLreturnO If your C function is a procedure i e if it returns void you must insert CAMLreturn0 at the end to replace C s implicit return Note some C compilers give bogus warnings about unused variables cam1__dummy_xxx at each use of CAMLparam and CAMLlocal You should ignore them Example void foo value vi value v2 value v3 CAMLparam3 v1 v2 v3 CAMLreturn0O Note
337. ompiled files By default the current directory is searched first then the standard library directory Directories added with I are searched after the current directory in the order in which they were given on the command line but before the standard library directory Directories can also be added to the search path once the toplevel is running with the directory directive section 9 2 labels Switch to the commuting label mode of compilation meaning that labeling rules are applied strictly and commutation between arguments is allowed See section 2 1 4 rectypes Allow arbitrary recursive types during type checking By default only recursive types where the recursion goes through an object type are supported unsafe See the corresponding option for ocamlc chapter 8 Turn bound checking off on array and string accesses the v i and s i constructs Programs compiled with unsafe are therefore slightly faster but unsafe anything can happen if the program accesses an array or string outside of its bounds w warning list Enable or disable warnings according to the argument warning list Unix The following environment variables are also consulted LC_CTYPE If set to iso_8859_1 accented characters from the ISO Latin 1 character set in string and character literals are printed as is otherwise they are printed as decimal escape sequences ddd 142 TERM When printing error messages the toplevel system attem
338. on a region of the file opened as fd The region starts at the current read write position for fd as set by 1seek and extends size bytes forward if size is positive size bytes backwards if size is negative or to the end of the file if size is zero A write lock set with F_LOCK or F_TLOCK prevents any other process from acquiring a read or write lock on the region A read lock set with F_RLOCK or F_TRLOCK prevents any other process from acquiring a write lock on the region but lets other processes acquire read locks on it Signals val kill pid int gt signal int gt unit kill pid sig sends signal number sig to the process with id pid type sigprocmask_command SIG_SETMASK SIG_BLOCK SIG_UNBLOCK val sigprocmask mode sigprocmask_command gt int list gt int list sigprocmask cmd sigs changes the set of blocked signals If cmd is SIG_SETMASK blocked signals are set to those in the list sigs If cmd is SIG_BLOCK the signals in sigs are added to the set of blocked signals If cmd is SIG_UNBLOCK the signals in sigs are removed from the set of blocked signals sigprocmask returns the set of previously blocked signals val sigpending unit gt int list Return the set of blocked signals that are currently pending val sigsuspend int list gt unit sigsuspend sigs atomically sets the blocked signals to sig and waits for a non ignored non blocked signal to be delivered On return the blocked signals are reset to their initial
339. one val insertion_sort a array gt unit lt fun gt References are also useful to write functions that maintain a current state between two calls to the function For instance the following pseudo random number generator keeps the last returned number in a reference let current_rand ref 0 val current_rand int ref contents 0 let random current_rand current_rand 25713 1345 current_rand val random unit gt int lt fun gt Again there is nothing magic with references they are implemented as a one field mutable record as follows type a ref mutable contents a type a ref mutable contents a let r r contents val a ref gt a lt fun gt let r newval r contents lt newval val a ref gt a gt unit lt fun gt 1 6 Exceptions Caml provides exceptions for signalling and handling exceptional conditions Exceptions can also be used as a general purpose non local control structure Exceptions are declared with the exception construct and signalled with the raise operator For instance the function below for taking the head of a list uses an exception to signal the case where an empty list is given exception Empty_list exception Empty_list let head 1 match 1 with gt raise Empty_list 18 hd tl gt hd val head a list gt a lt fun gt head 1
340. onstructor class type restricted_point_type object method get_x int method bump unit end class type restricted_point_type object method bump unit method get_x int end fun x restricted_point_type gt x restricted_point_type gt restricted_point_type lt fun gt In addition to documentation these class interfaces can be used to constrain the type of a class Both instance variables and concrete private methods can be hidden by a class type constraint Public and virtual methods however cannot class restricted_point x restricted_point x restricted_point_type class restricted_point int gt restricted_point_type Or equivalently class restricted_point restricted_point int gt restricted_point_type class restricted_point int gt restricted_point_type The interface of a class can also be specified in a module signature and used to restrict the inferred signature of a module module type POINT sig class restricted_point int gt object method get_x int method bump unit end end module type POINT sig class restricted_point int gt object method bump unit method get_x int end end module Point POINT struct class restricted_point restricted_point end module Point POINT Chapter 3 Objects in Caml 43 3 7 Inheritance We illustrate inheritance by defining a class of colored
341. or drawing text The interpretation of the arguments to set_font and set_text_size is implementation dependent val text_size string gt int int Return the dimensions of the given text if it were drawn with the current font and size Filling val fill_rect x int gt y int gt w int gt h int gt unit fill_rect x y w h fills the rectangle with lower left corner at x y width w and height h with the current color val fill_poly int int array gt unit Fill the given polygon with the current color The array contains the coordinates of the vertices of the polygon val fill_arc x int gt y int gt rx int gt ry int gt start int gt stop int gt unit Fill an elliptical pie slice with the current color The parameters are the same as for draw_arc 344 val fill_ellipse x int gt y int gt rx int gt ry int gt unit Fill an ellipse with the current color The parameters are the same as for draw_ellipse val fill_circle x int gt y int gt r int gt unit Fill a circle with the current color The parameters are the same as for draw_circle Images type image The abstract type for images in internal representation Externally images are represented as matrices of colors val transp color In matrices of colors this color represent a transparent point when drawing the corresponding image all pixels on the screen corresponding to a transparent pixel in the image will not be mod
342. or instance if you are allocating a finalized block holding an X Windows bitmap of w by h pixels and you d rather not have more than 1 mega pixels of unreclaimed bitmaps specify used w x h and max 1000000 Another way to describe the effect of the used and maz parameters is in terms of full GC cycles If you allocate many custom blocks with used maz 1 N the GC will then do one full cycle examining every object in the heap and calling finalization functions on those that are unreachable every N allocations For instance if used 1 and maz 1000 the GC will do one full cycle at least every 1000 allocations of custom blocks If your finalized blocks contain no pointers to out of heap resources or if the previous discussion made little sense to you just take used 0 and maz 1 But if you later find that the finalization functions are not called often enough consider increasing the used maz ratio 17 9 3 Accessing custom blocks The data part of a custom block v can be accessed via the pointer Data_custom_val v This pointer has type void and should be cast to the actual type of the data stored in the custom block The contents of custom blocks are not scanned by the garbage collector and must therefore not contain any pointer inside the Caml heap In other terms never store a Caml value in a custom block and do not use Field Store_field nor modify to access the data part of a custom block Conversely any C data structu
343. ore Oo copy takes an object with any methods represented by the ellipsis and returns an object of the same type The type of Oo copy is different from type lt gt gt lt gt as each ellipsis represents a different set of methods Ellipsis actually behaves as a type variable let p new point 5 val p point lt obj gt let q Oo copy p val q point lt obj gt q move 7 p get_x q get_x int int 5 12 In fact 0o copy p will behave as p copy assuming that a public method copy with body lt gt has been defined in the class of p Objects can be compared using the generic comparison functions and lt gt Two objects are equal if and only if they are physically equal In particular an object and its copy are not equal let q Oo copy p val q point lt obj gt p q P Ps bool bool false true Other generic comparissons such as lt lt can also be used on objects The relation lt defines an unspecified but strict ordering on objets The ordering relationship between two objects is fixed once for all after the two objects have been created and it is not affected by mutation of fields Cloning and override have a non empty intersection They are interchangeable when used within an object and without overriding any field class copy object method copy lt gt end class copy object a method copy a end class copy
344. ot a valid representation of an integer val read_float unit gt float Flush standard output then read one line from standard input and convert it to a floating point number The result is unspecified if the line read is not a valid representation of a floating point number 232 General output functions type open_flag Open_rdonly Open_wronly Open_append Open_creat Open_trunc Open_excl Open_binary Open_text Open_nonblock val val val val val val Opening modes for open_out_gen and open_in_gen Open_rdonly open for reading Open_wronly open for writing Open_append open for appending Open_creat create the file if it does not exist Open_trunc empty the file if it already exists Open_excl fail if the file already exists Open_binary open in binary mode no conversion Open_text open in text mode may perform conversions Open_nonblock open in non blocking mode open_out string gt out_channel Open the named file for writing and return a new output channel on that file positionned at the beginning of the file The file is truncated to zero length if it already exists It is created if it does not already exists Raise Sys_error if the file could not be opened open_out_bin string gt out_channel Same as open_out but the file is opened in binary mode so that no translation takes place during writes On operating systems that do not distinguish between text mode an
345. ou can override this behaviour by specifying your own help option in speclist exception Bad of string Functions in spec or anonfun can raise Arg Bad with an error message to reject invalid arguments val usage keywords string spec string list gt errmsg string gt unit Arg usage speclist usage_msg prints an error message including the list of valid options This is the same message that Arg parse prints in case of error speclist and usage_msg are the same as for Arg parse val current int ref Position in Sys argv of the argument being processed You can change this value e g to force Arg parse to skip some arguments 19 2 Module Array array operations val length a array gt int Return the length number of elements of the given array val get a array gt int gt a Array get a n returns the element number n of array a The first element has number 0 The last element has number Array length a 1 Raise Invalid_argument Array get if n is outside the range 0 to Array length a 1 You can also write a n instead of Array get a n val set a array gt int gt a gt unit Array set a n x modifies array a in place replacing element number n with x Raise Invalid_argument Array set if n is outside the range 0 to Array length a 1 You can also write a n lt x instead of Array set a n x val make int gt a gt a array val create int gt a gt
346. output channel The only reliable way to read it back is through the input_binary_int function The format is compatible across all machines for a given version of Objective Caml output_value out_channel gt a gt unit Write the representation of a structured value of any type to a channel Circularities and sharing inside the value are detected and preserved The object can be read back by the function input_value See the description of module Marshal for more information output_value is equivalent to Marshal to_channel with an empty list of flags seek_out out_channel gt int gt unit seek_out chan pos sets the current writing position to pos for channel chan This works only for regular files On files of other kinds such as terminals pipes and sockets the behavior is unspecified pos_out out_channel gt int Return the current writing position for the given channel out_channel_length out_channel gt int Return the total length number of characters of the given channel This works only for regular files On files of other kinds the result is meaningless close_out out_channel gt unit Close the given channel flushing all buffered write operations The behavior is unspecified if any of the functions above is called on a closed channel set_binary_mode_out out_channel gt bool gt unit set_binary_mode_out oc true sets the channel oc to binary mode no translations take place during output
347. owever the bug might be fixed more safely by the following definition class safe_account object inherit account as unsafe method deposit x if zero leq x then unsafe deposit x Chapter 5 Advanced examples with classes and modules 69 else raise Invalid_argument deposit end class safe_account object val mutable balance Euro c method balance Euro c method deposit Euro c gt unit method withdraw Euro c gt Euro c end In particular this does not require the knowledge of the implementation of the method deposit To keep trace of operations we extend the class with a mutable field history and a private method trace to add an operation in the log Then each method to be traced is redefined type a operation Deposit of a Retrieval of a type a operation Deposit of a Retrieval of a class account_with_history object self inherit safe_account as super val mutable history method private trace x history lt x history method deposit x self trace Deposit x super deposit x method withdraw x self trace Retrieval x super withdraw x method history List rev history end class account_with_history object val mutable balance Euro c val mutable history Euro c operation list method balance Euro c method deposit Euro c gt unit method history Euro c operation list method private trace Euro c operation gt unit
348. ox_printing 323 get_ellipsis_text 251 get_error_when_null_denominator 322 get_floating_precision 323 get_formatter_output_functions 251 get_image 344 get_margin 249 get_max_boxes 249 get_max_indent 249 get_normalize_ratio 322 get_normalize_ratio_when_printing 323 getcwd 291 303 getegid 309 getenv 291 298 geteuid 309 getgid 309 getgrgid 310 getgrnam 310 getgroups 309 gethostbyaddr 314 gethostbyname 314 gethostname 313 getitimer 308 getlogin 309 getpeername 312 getpid 299 getppid 299 getprotobyname 314 getprotobynumber 314 getpwnam 310 getpwuid 310 getservbyname 314 getservbyport 314 getsockname 312 getsockopt 312 gettimeofday 307 getuid 309 global_replace 327 global_substitute 328 gmtime 307 Graphic_failure exception 340 Graphics module 340 green 341 grid 353 group_beginning 327 group_end 327 gt_num 321 guard 336 handle_unix_error 297 hash 261 hash_param 262 HashedType module type 261 Hashtbl module 259 hd 269 header_size 276 id 332 ignore 229 in_channel_length 235 in_channel_of_descr 300 incr 236 incr_num 321 INDEX TO THE LIBRARY index 290 index_from 290 inet_addr_any 310 inet_addr_of_string 310 init 241 283 349 input 234 245 input_binary_int 235 input_byte 235 input_char 234 input_line 234 input_value 235 int 283 359 int1i6_signed 359 inti6_unsigned 359 int32 359 Int32 modu
349. p cp gt point val to_point lt get_offset int get_x int move int gt unit gt gt point lt fun gt In this case the function colored_point_to_point is an instance of the function to_point This is not always true however The fully explicit coercion is more precise and is sometimes unavoidable Here is an example where the shorter form fails class virtual c object method virtual m c end class virtual c object method virtual m c end class c object self inherit c method m self gt c method m 1 end This expression cannot be coerced to type c lt m c gt it has type lt mo es mAg tak ee gt but is here used with type lt m b m a gt as b Type c lt m c gt is not compatible with type b Self type cannot be unified with a closed object type The type of the coercion to type c can be seen here function x gt x gt c Km a gt as a gt c lt fun gt As class c inherits from class c its method m must have type c On the other hand in expression self gt c the type of self and the domain of the coercion above must be unified That is the type of the method m in self i e c is also the type of self So the type of self is c This is a contradiction as the type of self has a method m whereas type c does not The desired coercion of type lt m c gt gt c can be obtained by usi
350. pe names A structure will match a signature if the structure provides definitions implementations for all the names specified in the signature and possibly more and these definitions meet the type requirements given in the signature For compatibility with Caml Light an optional is allowed after each specification in a signature The has no semantic meaning Value specifications A specification of a value component in a signature is written val value name typexpr where value name is the name of the value and typexpr its expected type The form external value name typexpr external declaration is similar except that it requires in addition the name to be implemented as the external function specified in external declaration see chapter 17 Chapter 6 The Objective Caml language 119 Type specifications A specification of one or several type components in a signature is written type typedef and typedef and consists of a sequence of mutually recursive definitions of type names Each type definition in the signature specifies an optional type equation typexp and an optional type representation constr decl or label decl The implementation of the type name in a matching structure must be compatible with the type expression specified in the equation if given and have the specified representation if given Conversely users of that signature will be able to rely on the type equation or type representation i
351. plit sep regexp gt string gt max int gt string list Same as split but splits into at most n substrings where n is the extra integer parameter val split_delim sep regexp gt string gt string list val bounded_split_delim sep regexp gt string gt max int gt string list Same as split and bounded_split but occurrences of the delimiter at the beginning and at the end of the string are recognized and returned as empty strings in the result For instance split_delim regexp abc returns abc while split with the same arguments returns abc type split_result Text of string Delim of string val full_split sep regexp gt string gt split_result list val bounded_full_split sep regexp gt string gt int gt split_result list Same as split_delim and bounded_split_delim but returns the delimiters as well as the substrings contained between delimiters The former are tagged Delim in the result list the latter are tagged Text For instance full_split regexp ab returns Delim Text ab Delim Chapter 22 The str library regular expressions and string processing 329 Extracting substrings val string_before string gt int gt string string_before s n returns the substring of all characters of s that precede position n excluding the character at position n val string_after string gt int gt string string_after s n returns the substring of all characte
352. points that inherits from the class of points This class has all instance variables and all methods of class point plus a new instance variable c and a new method color class colored_point x c string object inherit point x val c c method color c end class colored_point int gt string gt object val c string val mutable x int method color string method get_offset int method get_x int method move int gt unit end let p new colored_point 5 red val p colored_point lt obj gt p get_x p color int string 5 red A point and a colored point have incompatible types since a point has no method color However the function get_x below is a generic function applying method get_x to any object p that has this method and possibly some others which are represented by an ellipsis in the type Thus it applies to both points and colored points let get_succ_x p p get_x 1 val get_succ_x lt get_x int gt gt int lt fun gt get_succ_x p get_succ_x p int 8 Methods need not be declared previously as shown by the example let set_x p p set_x val set_x lt set_x a gt gt a lt fun gt let incr p set_x p get_succ_x p val incr lt get_x int set_x int gt a gt gt a lt fun gt 44 3 8 Multiple inheritance Multiple inheritance is allowed Only the las
353. pr instead of lt repr k repr gt would not behave well with inheritance in a subclass money3 of money2 the times method would return an object of class money2 but not of class money3 as would be expected The class money could naturally carry another binary method Here is a direct definition class money x object self a val repr x method value repr method print print_float repr method times k lt repr k x gt method leq p a repr lt p value method plus p a lt repr x p value gt end class money float gt object a val repr float method leq a gt bool method plus a gt a method print unit method times float gt a method value float end Chapter 3 Objects in Caml 57 3 15 Friends The above class money reveals a problem that often occurs with binary methods In order to interact with other objects of the same class the representation of money objects must be revealed using a method such as value If we remove all binary methods here plus and leq the representation can easily be hidden inside objects by removing the method value as well However this is not possible as long as some binary requires access to the representation on object of the same class but different from self class safe_money x object self a val repr x method print print_float repr method times k lt
354. printed on standard error but not propagated back to the parent thread Similarly the result of the application funct arg is discarded and not directly accessible to the parent thread val self unit gt t Return the thread currently executing val id t gt int Return the identifier of the given thread A thread identifier is an integer that identifies uniquely the thread It can be used to build data structures indexed by threads val exit unit gt unit Terminate prematurely the currently executing thread val kill t gt unit Terminate prematurely the thread whose handle is given This functionality is available only with bytecode level threads Suspending threads val delay float gt unit delay d suspends the execution of the calling thread for d seconds The other program threads continue to run during this time val join t gt unit join th suspends the execution of the calling thread until the thread th has terminated Chapter 23 The threads library 333 val wait_read Unix file_descr gt unit val wait_write Unix file_descr gt unit Suspend the execution of the calling thread until at least one character is available for reading wait_read or one character can be written without blocking wait_write on the given Unix file descriptor val wait_timed_read Unix file_descr gt timeout float gt bool val wait_timed_write Unix file_descr gt timeout float gt bool Same as wait_read
355. provided and you should normally not have to change them set processcount count Set the maximum number of checkpoints to count More checkpoints facilitate going far back in time but use more memory and create more Unix processes As checkpointing is quite expensive it must not be done too often On the other hand backward execution is faster when checkpoints are taken more often In particular backward single stepping is more responsive when many checkpoints have been taken just before the current time To fine tune the checkpointing strategy the debugger does not take checkpoints at the same frequency for long displacements e g run and small ones e g step The two variables bigstep and smallstep contain the number of events between two checkpoints in each case set bigstep count Set the number of events between two checkpoints for long displacements set smallstep count Set the number of events between two checkpoints for small displacements The following commands display information on checkpoints and events info checkpoints Print a list of checkpoints info events module Print the list of events in the given module the current module by default Chapter 15 The debugger ocamldebug 185 15 8 8 User defined printers Just as in the toplevel system section 9 2 the user can register functions for printing values of certain types For technical reasons the debugger cannot call printing functions that reside in
356. pts to underline visually the location of the error It consults the TERM variable to determines the type of output terminal and look up its capabilities in the terminal database 9 2 Toplevel directives The following directives control the toplevel behavior load files in memory and trace program execution quit Exit the toplevel loop and terminate the ocaml command labels bool Switch to commuting label style if argument is true or back to classic non commuting style if argument is false See section 2 1 4 warnings warning list Enable or disable warnings according to the argument directory dir name Add the given directory to the list of directories searched for source and compiled files cd dir name Change the current working directory load file name Load in memory a bytecode object file cmo file produced by the batch compiler ocamlc use file name Read compile and execute source phrases from the given file This is textual inclusion phrases are processed just as if they were typed on standard input The reading of the file stops at the first error encountered install_printer printer name This directive registers the function named printer name a value path as a printer for objects whose types match the argument type of the function That is the toplevel loop will call printer name when it has such an object to print The printing function printer name must use the Fo
357. push a gt unit end let stack_fold s a stack3 f x let accu ref x in s iter fun e gt accu f accu e laccu val stack_fold a stack3 gt b gt a gt b gt b gt b lt fun gt 5 2 2 Hashtbl A simplified version of object oriented hash tables should have the following class type class type a b hash_table object method find a gt b method add a gt b gt unit end class type a b hash_table object method add a gt b gt unit method find a gt b end A simple implementation which is quite reasonable for small hastables is to use an association list class a b small_hashtbl a b hash_table object val mutable table method find key List assoc key table method add key valeur table lt key valeur table end class a b small_hashtbl a b hash_table A better implementation and one that scales up better is to use a true hash tables whose elements are small hash tables 78 class a b hashtbl size a b hash_table object self val table Array init size fun i gt new small_hashtbl method private hash key Hashtbl hash key mod Array length table method find key table self hash key find key method add key table self hash key add key end class a b has
358. q that expects an argument of type money since it accesses its value method Considering m of type comparable would allow to call method leq on m with an argument that does not have a method value which would be an error Similarly the type money2 below is not a subtype of type money class money2 x object inherit money x method times k lt repr k repr gt end class money2 float gt 56 object a val repr float method leq a gt bool method times float gt a method value float end It is however possible to define functions that manipulate objects of type either money or money2 the function min will return the minimum of any two objects whose type unifies with comparable The type of min is not the same as comparable gt comparable gt comparable as the abbreviation comparable hides a type variable an ellipsis Each occurrence of this abbreviation generates a new variable let min x comparable y if x leq y then x else y val min comparable as a gt a gt a lt fun gt This function can be applied to objects of type money or money2 min new money 1 3 mew money 3 1 value float 1 300000 min mew money2 5 0 new money2 3 14 value float 3 140000 More examples of binary methods can be found in sections 5 2 1 and 5 2 3 Notice the use of functional update for method times Writing new money2 k re
359. r e when possible allows useful partial applications We explain here the rules we applied when labeling Objective Caml libraries To speak in an object oriented way one can consider that each function has a main argument its object and other arguments related with its action the parameters To permit the combination of functions through functionals in commuting label mode the object will not be labeled Its role is clear by the function itself The parameters are labeled with names reminding either of their nature or role Best labels combine in their meaning nature and role When this is not possible the role is to prefer since the nature will often be given by the type itself Obscure abbreviations should be avoided List map f a gt b gt a list gt b list output out_channel gt buf string gt pos int gt len int gt unit When there are several objects of same nature and role they are all left unlabeled List iter2 f a gt b gt c gt a list gt b list gt unit When there is no preferable object all arguments are labeled Sys rename src string gt dst string gt unit String blit src string gt src_pos int gt dst string gt dst_pos int gt len int gt unit However when there is only one argument it is often left unlabeled Format open_hvbox int gt unit In the standard library this principle also applies to functions of two or three arguments
360. r gt member x tl end module Set functor Elt ORDERED_TYPE gt sig type element Elt t and set element list val empty a list val add Elt t gt Elt t list gt Elt t list val member Elt t gt Elt t list gt bool end By applying the Set functor to a structure implementing an ordered type we obtain set operations for this type module OrderedString struct type t string let cmp x y if x y then Equal else if x lt y then Less else Greater end module OrderedString sig type t string val cmp a gt a gt comparison end module StringSet Set OrderedString module StringSet sig type element OrderedString t and set element list val empty a list val add OrderedString t gt OrderedString t list gt OrderedString t list val member OrderedString t gt OrderedString t list gt bool end Chapter 4 The module system 63 StringSet member bar StringSet add foo StringSet empty bool false 4 4 Functors and type abstraction As in the PrioQueue example it would be good style to hide the actual implementation of the type set so that users of the structure will not rely on sets being lists and we can switch later to another more efficient representation of sets without breaking their code This can be achieved by restricting Set by a suitable functor signature module type SETFUNCTOR functor Elt ORDERED_TYPE gt s
361. r or 88 Prefix and infix symbols infix symbol lt gt 7 1 amp 4 operator char prefix symbol 7 operator char operator char 8 l amp l l 1 z1 lt l l gt 17ele til Sequences of operator characters such as lt gt or are read as a single token from the infix symbol or prefix symbol class These symbols are parsed as prefix and infix operators inside expressions but otherwise behave much as identifiers Keywords The identifiers below are reserved as keywords and cannot be employed otherwise and as assert asr begin class closed constraint do done downto else end exception external false for fun function functor if in include inherit land lazy let lor 1sl lsr lxor match method mod module mutable new of open or parser private rec sig struct then to true try type val virtual when while with The following character sequences are also keywords amp A gt i EG cE me 33 lt I lt lt 1 gt gt gt a Ambiguities Lexical ambiguities are resolved according to the longest match rule when a character sequence can be decomposed into two tokens in several different ways the decomposition retained is the one with the longest first token Line number directives linenum directive 0 9 0 9 string character Preprocessors that generate Caml source code can insert line number directives
362. r all optional parameters let twice f x int f f x val twice int gt int gt int gt int lt fun gt twice bump 2 int 8 This transformation is coherent with the intended semantics including side effects That is if the application of optional parameters shall produce side effects these are delayed until the received function is really applied to an argument Chapter 2 Labels and variants 29 2 1 4 Commuting label mode The commuting label mode allows a freer syntax at the constraint that you must write all labels both in function definition and application and that labels must match in all types If this is your first reading of this tutorial or if you are satisfied with classic mode you can probably skip the rest of this section You need not know anything more on labels In particular you should not be bothered by the fact that some libraries are written in commuting label mode the mode in which a library is written and the mode in which one uses it are completely independent You can switch to commuting label mode giving the labels flag to the various Objective Caml compilers At the toplevel you can also switch from classic mode to commuting label mode and back with the labels pragma labels true In commuting label mode formal parameters and arguments are only matched according to their respective labels This allows commuting arguments in applications One can also partially appl
363. r to manually erase all copies class backup object self mytype val mutable copy None method save copy lt Some lt gt method restore match copy with Some x gt x None gt self method clear copy lt None end 54 class backup object a val mutable copy a option method clear unit method restore a method save unit end class a backup_ref x object inherit a ref x inherit backup end class a backup_ref 2a gt object b val mutable copy b option val mutable x a method clear unit method get a method restore b method save unit method set a gt unit end let p new backup_ref O in p save p set 1 p save p set 2 get p 0 get p 1 get p 2 get p 3 get p 4 int list 2 1 0 0 0J 3 13 Recursive classes Recursive classes can be used to define objects whose types are mutually recursive class window object val mutable top_widget None widget option method top_widget top_widget end and widget w window object val window w method window window end class window object val mutable top_widget widget option method top_widget widget option end class widget window gt object val window window method window window end Although their types are mutually recursive the classes widget and window are themselves inde pend
364. range 0 to String length s 1 You can also write s n lt c instead of String set s n c create int gt string String create n returns a fresh string of length n The string initially contains arbitrary characters Raise Invalid_argument ifn lt O orn gt Sys max_string_length make int gt char gt string String make n c returns a fresh string of length n filled with the character c Raise Invalid_argument ifn lt 0 orn gt Sys max_string_length copy string gt string Return a copy of the given string sub string gt pos int gt len int gt string String sub s start len returns a fresh string of length len containing the characters number start to start len 1 of string s Raise Invalid_argument if start and len do not designate a valid substring of s that is if start lt 0 or len lt 0 or start len gt String length s fill string gt pos int gt len int gt char gt unit String fill s start len c modifies string s in place replacing the characters number start to start len 1 by c Raise Invalid_argument if start and len do not designate a valid substring of s blit src string gt src_pos int gt dst string gt dst_pos int gt len int gt unit String blit src srcoff dst dstoff len copies len characters from string src starting at character number srcoff to string dst starting at character number dstoff It works correctly even if src and dst are the s
365. ray of strings with the format variable value val getenv string gt string Return the value associated to a variable in the process environment Raise Not_found if the variable is unbound This function is identical to Sys getenv val putenv string gt string gt unit Unix putenv name value sets the value associated to a variable in the process environment name is the name of the environment variable and value its new associated value Process handling type process_status WEXITED of int WSIGNALED of int WSTOPPED of int The termination status of a process WEXITED means that the process terminated normally by exit the argument is the return code WSIGNALED means that the process was killed by a signal the argument is the signal number WSTOPPED means that the process was stopped by a signal the argument is the signal number type wait_flag WNOHANG WUNTRACED Flags for waitopt and waitpid WNOHANG means do not block if no child has died yet but immediately return with a pid equal to 0 WUNTRACED means report also the children that receive stop signals val execv prog string gt args string array gt unit execv prog args execute the program in file prog with the arguments args and the current process environment val execve prog string gt args string array gt env string array gt unit Same as execv except that the third argument provides the environment to the program executed
366. re not containing heap pointers can be stored in a custom block 17 9 4 Writing custom serialization and deserialization functions The following functions defined in lt caml intext h gt are provided to write and read back the contents of custom blocks in a portable way Those functions handle endianness conversions when e g data is written on a little endian machine and read back on a big endian machine Chapter 17 Interfacing C with Objective Caml 217 Function Action serialize_int_1 Write a 1 byte integer serialize_int_2 Write a 2 byte integer serialize_int_4 Write a 4 byte integer serialize_int_8 Write a 8 byte integer serialize_float_4 Write a 4 byte float serialize_float_8 Write a 8 byte float serialize_block_1 Write an array of 1 byte quantities serialize_block_2 Write an array of 2 byte quantities serialize_block_4 Write an array of 4 byte quantities serialize_block_8 Write an array of 8 byte quantities deserialize_uint_1 Read an unsigned 1 byte integer deserialize_sint_1 Read a signed 1 byte integer deserialize_uint_2 Read an unsigned 2 byte integer deserialize_sint_2 Read a signed 2 byte integer deserialize_uint_4 Read an unsigned 4 byte integer deserialize_sint_4 Read a signed 4 byte integer deserialize_uint_8 Read an unsigned 8 byte integer deserialize_sint_8 Read a signed 8 byte integer deserialize_float_4 Read a 4 byte float deserialize_float_8 Read an 8 byte float deserialize_bl
367. re called from any thread thus they cannot not acquire any mutex Anything reachable from the closure of finalisation functions is considered reachable so the following code will not work let v in Gc finalise fun x gt v Instead you should write let f fun x gt 3 let v in Gc finalise f v The f function can use all features of O Caml including assignments that make the value reachable again indeed the value is already reachable from the stack during the execution of the function It can also loop forever in this case the other finalisation functions will be called during the execution of f It can call Gc finalise on v or other values to register other functions or even itself It can raise an exception in this case the exception will interrupt whatever the program was doing when the function was called Gc finalise will raise Invalid_argument if v is not heap allocated Some examples of values that are not heap allocated are integers constant constructors booleans the empty array the empty list the unit value The exact list of what is heap allocated or not is implementation dependent You should also be aware that some optimisations will duplicate some immutable values especially floating point numbers when stored into arrays so they can be finalised and collected while another copy is still in use by the program Chapter 19 The standard library 259 19 10 Module Genlex a generic lexical analyz
368. re finite sequences of characters The current implementation supports strings con taining up to 24 6 characters 16777210 characters 6 2 2 Tuples Tuples of values are written v1 Un standing for the n tuple of values v to vn The current implementation supports tuple of up to 27 1 elements 4194303 elements 6 2 3 Records Record values are labeled tuples of values The record value written field v1 field un associates the value v to the record field field for i 1 n The current implementation supports records with up to 2 1 fields 4194303 fields 90 6 2 4 Arrays Arrays are finite variable sized sequences of values of the same type The current implementation supports arrays containing to 2 1 elements 4194303 elements 6 2 5 Variant values Variant values are either a constant constructor or a pair of a non constant constructor and a value The former case is written cconstr the latter case is written ncconstr v where v is said to be the argument of the non constant constructor ncconstr The following constants are treated like built in constant constructors Constant Constructor false the boolean false true the boolean true O the unit value the empty list The current implementation limits the number of distinct constructors in a given variant type to at most 249 6 2 6 Polymorphic variants Polymorphic variants are an alternate form of v
369. re than max_overhead percent of the amount of live data If max_overhead is set to 0 heap compaction is triggered at the end of each major GC cycle this setting is intended for testing purposes only If max_overhead gt 1000000 compaction is never triggered Default 1000000 verbose This value controls the GC messages on standard error output It is a sum of some of the following flags to print messages on the corresponding events 0x01 Start of major GC cycle 0x02 Minor collection and major GC slice 0x04 Growing and shrinking of the heap 0x08 Resizing of stacks and memory manager tables 0x10 Heap compaction 0x20 Change of GC parameters 0x40 Computation of major GC slice size 0x80 Calling of finalisation functions Default 0 stack_limit The maximum size of the stack in words This is only relevant to the byte code runtime as the native code runtime uses the operating system s stack Default 256k stat unit gt stat Return the current values of the memory management counters in a stat record counters unit gt int int int Return minor_words promoted_words major_words Much faster than stat get unit gt control Return the current values of the GC parameters in a control record set control gt unit set r changes the GC parameters according to the control record r The normal usage is Gc set Gc get with Gc verbose 13 minor unit gt unit Trigger a minor collection m
370. reakpoints can only be set at events Thus events play the role of line numbers in debuggers for conventional languages During program execution a counter is incremented at each event encountered The value of this counter is referred as the current time Thanks to reverse execution it is possible to jump back and forth to any time of the execution Here is where the debugger events written bowtie are located in the source code e Following a function application arg bowtie e On entrance to a function fun x y z gt bowtie e On each case of a pattern matching definition function match with construct try with construct 178 function pati gt bowtie expri evar patN gt bowtie exprN e Between subexpressions of a sequence expri bowtie expr2 bowtie bowtie exprN e In the two branches of a conditional expression if cond then bowtie expri else bowtie expr2 e At the beginning of each iteration of a loop while cond do bowtie body done for i a to b do bowtie body done Exceptions A function application followed by a function return is replaced by the compiler by a jump tail call optimization In this case no event is put after the function application 15 4 2 Starting the debugged program The debugger starts executing the debugged program only when needed This allows setting brea points or assigning debugger variables before execution starts There are several ways to start execution
371. rect the standard output of the compiler to a mli file and edit that file to remove all declarations of unexported names I directory Add the given directory to the list of directories searched for compiled interface files cmi and compiled object code files cmo By default the current directory is searched first then the standard library directory Directories added with I are searched after the current directory in the order in which they were given on the command line but before the standard library directory impl filename Compile the file filename as an implementation file even if its extension is not ml intf filename Compile the file filename as an interface file even if its extension is not m1i labels Switch to the commuting label mode of compilation meaning that labeling rules are applied strictly and commutation between labeled arguments is allowed See section 2 1 4 This mode cannot be used to compile a program written in the default classic style but modules written in the two styles can be mixed in the same application linkall Force all modules contained in libraries to be linked in If this flag is not given unreferenced modules are not linked in When building a library a flag setting the linkall flag forces 134 all subsequent links of programs involving that library to link all the modules contained in the library make runtime Build a custom runtime system in the file specified by op
372. ression val replace_first pat regexp gt templ string gt string gt string Same as global_replace except that only the first substring matching the regular expression is replaced 328 val global_substitute pat regexp gt subst string gt string gt string gt string global_substitute regexp subst s returns a string identical to s except that all substrings of s that match regexp have been replaced by the result of function subst The function subst is called once for each matching substring and receives s the whole text as argument val substitute_first pat regexp gt subst string gt string gt string gt string Same as global_substitute except that only the first substring matching the regular expression is replaced val replace_matched templ string gt string gt string replace_matched repl s returns the replacement text repl in which 1 2 etc have been replaced by the text matched by the corresponding groups in the most recent matching operation s must be the same string that was matched during this matching operation Splitting val split sep regexp gt string gt string list split r s splits s into substrings taking as delimiters the substrings that match r and returns the list of substrings For instance split regexp t s splits s into blank separated words An occurrence of the delimiter at the beginning and at the end of the string is ignored val bounded_s
373. result of Int32 rem x y is not specified and depends on the platform Chapter 19 The standard library 263 val val val val val val val val val val val val val succ int32 gt int32 Successor Int32 succ x is Int32 add x 1i pred int32 gt int32 Predecessor Int32 pred x is Int32 sub x 1i abs int32 gt int32 Return the absolute value of its argument max_int int32 The greatest representable 32 bit integer 23 1 min_int int32 The smallest representable 32 bit integer 23 logand int32 gt int32 gt int32 Bitwise logical and logor int32 gt int32 gt int32 Bitwise logical or logxor int32 gt int32 gt int32 Bitwise logical exclusive or lognot int32 gt int32 Bitwise logical negation shift_left int32 gt int gt int32 Int32 shift_left x y shifts x to the left by y bits shift_right int32 gt int gt int32 Int32 shift_right x y shifts x to the right by y bits This is an arithmetic shift the sign bit of x is replicated and inserted in the vacated bits shift_right_logical int32 gt int gt int32 Int32 shift_right_logical x y shifts x to the right by y bits This is a logical shift zeroes are inserted in the vacated bits regardless of the sign of x of_int int gt int32 Convert the given integer type int to a 32 bit integer type int32 264 val val val val val val to_int int32 gt in
374. rmat library module to produce its output otherwise its output will not be correctly located in the values printed by the toplevel loop remove_printer printer name Remove the named function from the table of toplevel printers trace function name After executing this directive all calls to the function named function name will be traced That is the argument and the result are displayed for each call as well as the exceptions escaping out of the function raised either by the function itself or by another function it calls If the function is curried each argument is printed as it is passed to the function Chapter 9 The toplevel system ocaml 143 untrace function name Stop tracing the given function untrace_all Stop tracing all functions traced so far print_depth n Limit the printing of values to a maximal depth of n The parts of values whose depth exceeds n are printed as ellipsis print_length n Limit the number of value nodes printed to at most n Remaining parts of values are printed as ellipsis 9 3 The toplevel and the module system Toplevel phrases can refer to identifiers defined in compilation units with the same mechanisms as for separately compiled units either by using qualified names Modulename localname or by using the open construct and unqualified names see section 6 3 However before referencing another compilation unit an implementation of that unit must be
375. rmatter gt int gt unit pp_open_hvbox formatter gt int gt unit pp_open_hovbox formatter gt int gt unit pp_open_box formatter gt int gt unit pp_close_box formatter gt unit gt unit pp_print_string formatter gt string gt unit pp_print_as formatter gt int gt string gt unit pp_print_int formatter gt int gt unit pp_print_float formatter gt float gt unit pp_print_char formatter gt char gt unit pp_print_bool formatter gt bool gt unit pp_print_break formatter gt int gt int gt unit pp_print_cut formatter gt unit gt unit pp_print_space formatter gt unit gt unit pp_force_newline formatter gt unit gt unit pp_print_flush formatter gt unit gt unit pp_print_newline formatter gt unit gt unit pp_print_if_newline formatter gt unit gt unit pp_open_tbox formatter gt unit gt unit pp_close_tbox formatter gt unit gt unit pp_print_tbreak formatter gt int gt int gt unit pp_set_tab formatter gt unit gt unit pp_print_tab formatter gt unit gt unit pp_set_margin formatter gt int gt unit pp_get_margin formatter gt unit gt int pp_set_max_indent formatter gt int gt unit pp_get_max_indent formatter gt unit gt int pp_set_max_boxes formatter gt int gt unit pp_get_max_boxes formatter gt unit
376. rn expr in expr The only difference with the let construct described above is that the bindings of names to values performed by the pattern matching are considered already performed when the expressions expr to expr are evaluated That is the expressions expr to expr can reference identifiers that are bound by one of the patterns pattern pattern and expect them to have the same value as in expr the body of the let rec construct The recursive definition is guaranteed to behave as described above if the expressions expr to expr are function definitions fun or function and the patterns pattern pattern are just value names as in let rec name fun and and name fun in expr 104 This defines name name as mutually recursive functions local to expr The behavior of other forms of let rec definitions is implementation dependent The current implementation also supports a certain class of recursive definitions of non functional values such as let rec name 1 nameg and names 2 name in expr which binds name to the cyclic list 1 2 1 2 and name gt to the cyclic list 2 1 2 1 Informally the class of accepted definitions consists of those definitions where the defined names occur only inside function bodies or as argument to a data constructor 6 7 2 Control structures Sequence The expression expr expr evaluates expr first then exprs and returns the value of exprs
377. rray2 slice_left applies only to arrays with C layout val slice_right Ca b fortran_layout t gt y int gt a b fortran_layout Array1 t Extract a column one dimensional slice of the given two dimensional big array The integer parameter is the index of the column to extract See Genarray slice_right for more details Array2 slice_right applies only to arrays with Fortran layout external blit src a b c t gt dst a b c t gt unit Copy the first big array to the second big array See Genarray blit for more details external fill a b c t gt a gt unit Fill the given big array with the given value See Genarray fill for more details val of_array kind a b kind gt layout c layout gt a array array gt a b c t Build a two dimensional big array initialized from the given array of arrays val map_file Unix file_descr gt kind a b kind gt layout c layout gt shared bool gt dimi int gt dim2 int gt a b c t Memory mapping of a file as a two dimensional big array See Genarray map_file for more details end Three dimensional arrays The Array3 structure provides operations similar to those of Genarray but specialized to the case of three dimensional arrays module Array3 sig type Ca b c t The type of three dimensional big arrays whose elements have Caml type a representation kind b and memory l
378. rs With polymorphic variants this original assumption is removed That is a variant tag does not belong to any type in particular the type system will just check that it is an admissible value according to its use You need not define a type before using a variant tag A variant type will be inferred independently for each of its uses Basic use In programs polymorphic variants work like usual ones You just have to prefix their names with a backquote character On Off gt On Off list On Off Number 1 gt Number of int Number 1 let f function On gt 1 Off gt O Number n gt gt n val f lt On Off Number of int gt int lt fun gt List map f On Off int list 1 0 gt Off On list means that to match this list you should at least be able to match Off and On without argument lt On Off Number of int means that f may be applied to Off On both without argument or Number n where n is an integer The gt and lt inside the variant type shows that they may still be refined either by defining more tags or allowing less As such they contain an implicit type variable Both variant types appearing only once in the type the implicit type variables they constrain are not shown The above variant types were polymorphic allowing further refinement When writing type annot
379. rs of s that follow position n including the character at position n val first_chars string gt len int gt string first_chars s n returns the first n characters of s This is the same function as string_before val last_chars string gt len int gt string last_chars s n returns the last n characters of s 330 Chapter 23 The threads library The threads library allows concurrent programming in Objective Caml It provides multiple threads of control also called lightweight processes that execute concurrently in the same memory space Threads communicate by in place modification of shared data structures or by sending and receiving data on communication channels The threads library is implemented by time sharing on a single processor It will not take advantage of multi processor machines Using this library will therefore never make programs run faster However many programs are easier to write when structured as several communicating processes Unix Programs that use the threads library must be linked as follows ocamlc thread other options threads cma other files The thread option selects a special thread safe version of the standard library see chap ter 8 The thread option must also be given when compiling any source file that references modules from the thread library Thread Mutex The default thread implementation cannot be used in native code programs compiled with ocamlopt If your opera
380. rse_error Raised when a parser encounters a syntax error Can also be raised from the action part of a grammar rule to initiate error recovery 19 22 Module Printexc a catch all exception handler val catch a gt b gt a gt b Printexc catch fn x applies fn to x and returns the result If the evaluation of fn x raises any exception the name of the exception is printed on standard error output and the programs aborts with exit code 2 Typical use is Printexc catch main where main with type unit gt unit is the entry point of a standalone program This catches and reports any exception that escapes the program val print a gt b gt a gt b Same as catch but re raise the stray exception after printing it instead of aborting the program val to_string exn gt string Printexc to_string e returns a string representation of e 19 23 Module Printf formatting printing functions val fprintf out_channel gt a out_channel unit format gt a fprintf outchan format argi argN formats the arguments arg1 to argN according to the format string format and outputs the resulting string on the channel outchan The format is a character string which contains two types of objects plain characters which are simply copied to the output channel and conversion specifications each of which causes conversion and printing of one argument Chapter 19 The standard library 281 Conversion
381. rview Here is a short listing by theme of the standard library modules 237 238 Data structures Char p 244 String p 288 Array p 240 List p 269 Sort p 286 Hashtbl p 259 Random p 283 Set p 283 Map p 273 Oo p 279 Stack p 286 Queue p 282 Buffer p 243 Lazy p 267 Weak p 293 Int32 p 262 Int64 p 264 Nativeint p 277 Input output Format p 247 Marshal p 275 Printf p 280 Digest p 245 Parsing Genlex p 259 Lexing p 268 Parsing p 279 Stream p 287 System interface Arg Callback Filename Gc Printexc Sys P ee u g 238 244 245 255 280 291 character operations string operations array operations list operations sorting and merging lists hash tables and hash functions pseudo random number generator sets over ordered types association tables over ordered types useful functions on objects last in first out stacks first in first out queues string buffers that grow on demand delayed evaluation references that don t prevent objects from being garbage collected operations on 32 bit integers operations on 64 bit integers operations on platform native integers pretty printing marshaling of data structures formatting printing functions MD5 message digest a generic lexer over streams the run time library for lexers generated by camllex the run time library for parsers generated by camlyacc basic functions over streams parsing of command line arguments registerin
382. s The following characters are considered as blanks space newline horizontal tabulation carriage return line feed and form feed Blanks are ignored but they separate adjacent identifiers literals and keywords that would otherwise be confused as one single identifier literal or keyword Comments Comments are introduced by the two characters with no intervening blanks and terminated by the characters with no intervening blanks Comments are treated as blank characters Comments do not occur inside string or character literals Nested comments are handled correctly 85 86 Identifiers ident letter _ letter 0 9 _ letter A Z a z Identifiers are sequences of letters digits _ the underscore character and the single quote starting with a letter or an underscore Letters contain at least the 52 lowercase and uppercase letters from the ASCII set The current implementation also recognizes as letters all accented characters from the ISO 8859 1 ISO Latin 1 set and also allows an underscore _ as the first character of an identifier All characters in an identifier are meaningful The current implementation places no limits on the number of characters of an identifier Integer literals integer literal 0 9 H Ox 0x 0 9 A Fla 7 i 00 0 7 Ob 0B 0 1 An integer literal is a sequence of one or more digits optionally preceded by a minus sig
383. s Search symbol allows to search a symbol either by its name like the bottom line of the viewer or more interestingly by its type Exact type searches for a type with exactly the same information as the pattern variables match only variables Included type allows to give only partial information the actual type may take more arguments and return more results and variables in the pattern match anything In both cases argument and tuple order is irrelevant and unlabeled arguments in the pattern match any label 14 3 Module walking Each module is displayed in its own window At the top a scrollable list of the defined identifiers If you click on one this will either create a new window if this is a sub module or display the signature for this identifier below Signatures are clickable Double clicking with the left mouse button on an identifier in a signature brings you to its signature inside its module box A single click on the right button pops up a menu displaying the type declaration for the selected identifier Its title when selectable also brings you to its signature At the bottom a series of buttons depending on the context e Show all displays the signature of the whole module e Detach copies the currently displayed signature in a new window to keep it e Impl and Intf bring you to the implementation or interface of the currently displayed signa ture if it is available Control S lets you search a string in
384. s If you do not give a default value you have access to their internal representation type a option None Some of a You can then provide different behaviors when an argument is present or not let bump step x match step with None gt x 2 Some y gt x y 33 val bump step int gt int gt int lt fun gt It may also be useful to relay a functional argument from a function call to another This can be done by prefixing the applied argument with This question mark disables the wrapping of optional argument in an option type let test2 x y test x y O O val test2 x int gt y int gt unit gt int int int lt fun gt test2 x None y int gt unit gt int int int lt fun gt 28 2 1 3 Labels and type inference While they provide an increased comfort for writing function applications labels and optional arguments have the pitfall that they cannot be inferred as completely as the rest of the language You can see it in the following example let bump_it bump x bump step 2 x val bump_it step int gt a gt b gt a gt b lt fun gt bump_it bump 1 This expression has type step int gt int gt int but is here used with type int gt int gt a While we intended the argument bump to be of type step int gt int gt int it is inferred as step int gt a gt b These two types being
385. s between generic big arrays and fixed dimension big arrays val genarray_of_array1 a b c Array1 t gt a b c Genarray t val genarray_of_array2 a b c Array2 t gt a b c Genarray t val genarray_of_array3 a b c Array3 t gt a b c Genarray t Return the generic big array corresponding to the given one dimensional two dimensional or three dimensional big array val arrayl_of_genarray a b c Genarray t gt a b c Array1 t Return the one dimensional big array corresponding to the given generic big array Raise Invalid_arg if the generic big array does not have exactly one dimension val array2_of_genarray a b c Genarray t gt a b c Array2 t Return the two dimensional big array corresponding to the given generic big array Raise Invalid_arg if the generic big array does not have exactly two dimensions val array3_of_genarray a b c Genarray t gt a b c Array3 t Return the three dimensional big array corresponding to the given generic big array Raise Invalid_arg if the generic big array does not have exactly three dimensions 28 2 Big arrays in the Caml C interface C stub code that interface C or Fortran code with Caml code as described in chapter 17 can exploit big arrays as follows 28 2 1 Include file The include file lt caml bigarray h gt must be included in the C stub file
386. s do not affect the graphics window This occurs independently of drawing into the backing store see the function remember_mode below Default display mode is on val remember_mode bool gt unit Set remember mode on or off When turned on drawings are done in the backing store when turned off the backing store is unaffected by drawings This occurs independently of drawing onto the graphics window see the function display_mode above Default remember mode is on Chapter 25 The dbm library access to NDBM databases The dbm library provides access to NDBM databases under Unix NDBM databases maintain key data associations where both the key and the data are arbitrary strings They support fairly large databases several gigabytes and can retrieve a keyed item in one or two file system accesses Refer to the Unix manual pages for more information Unix Programs that use the dbm library must be linked as follows ocamlc other options dbm cma other files ocamlopt other options dbm cmxa other files For interactive use of the dbm library do ocamlmktop o mytop dbm cma mytop Windows This library is not available 25 1 Module Dbm interface to the NDBM database type t The type of file descriptors opened on NDBM databases type open_flag Dbm_rdonly Dbm_wronly Dbm_rdwr Dbm_create Flags for opening a database see opendbm 347 348 exception Dbm_error of string val val val val val
387. s how the contents of the blocks are structured A tag lower than No_scan_tag indicates a structured block containing well formed values which is recursively traversed by the garbage collector A tag greater than or equal to No_scan_tag indicates a raw block whose contents are not scanned by the garbage collector For the benefits of ad hoc polymorphic primitives such as equality and structured input output structured and raw blocks are further classified according to their tags as follows Tag Contents of the block 0 to No_scan_tag 1 A structured block an array of Caml objects Each field is a value Closure_tag A closure representing a functional value The first word is a pointer to a piece of code the remaining words are value containing the environment String_tag A character string Double_tag A double precision floating point number Double_array_tag An array or record of double precision floating point num bers Abstract_tag A block representing an abstract datatype Custom_tag A block representing an abstract datatype with user defined finalization comparison hashing serialization and deserial ization functions atttached 17 2 3 Pointers outside the heap Any word aligned pointer to an address outside the heap can be safely cast to and from the type value This includes pointers returned by malloc and pointers to C variables of size at least one word obtained with the amp operator Ch
388. s specified in the event to the outside world and block until one of the communications succeed The result value of that communication is returned select a event list gt a Synchronize on an alternative of events select evl is shorthand for sync choose ev1 poll a event gt a option Non blocking version of sync offer all the communication possibilities specified in the event to the outside world and if one can take place immediately perform it and return Some r where r is the result value of that communication Otherwise return None without blocking 23 5 Module ThreadUnix thread compatible system calls This module reimplements some of the functions from Unix so that they only block the calling thread not all threads in the program if they cannot complete immediately See the documentation of the Unix module for more precise descriptions of the functions below Chapter 23 The threads library 337 Process handling val execv prog string gt args string array gt unit val execve prog string gt args string array gt env string array gt unit val execvp prog string gt args string array gt unit val wait unit gt int Unix process_status val waitpid mode Unix wait_flag list gt int gt int Unix process_status val system string gt Unix process_status Basic input output val read Unix file_descr gt buf string gt pos int gt len int gt int val write Uni
389. s to reflect the precedence and associativity of operators Pattern matching over streams is more powerful than on regular data structures as it allows recursive calls to parsing functions inside the patterns for matching sub components of the input stream See chapter 7 for more details 0 ct rec parse_expr parser lt e1 parse_mult e parse_more_adds e1 gt gt e and parse_more_adds e1 parser lt Kwd e2 parse_mult e parse_more_adds Sum e1 e2 gt gt e lt Kwd e2 parse_mult e parse_more_adds Diff e1 e2 gt gt e lt gt gt ef and parse_mult parser lt e1 parse_simple e parse_more_mults e1 gt gt e parse_more_mults e1 parser lt Kwd e2 parse_simple e parse_more_mults Prod e1 e2 gt gt e lt Kwd e2 parse_simple e parse_more_mults Quot e1 e2 gt gt e lt gt gt e1 and parse_simple parser lt Ident s gt gt Var s lt Int i gt gt Const float i lt Float f gt gt Const f lt Kwd e parse_expr Kwd gt gt e val parse_expr Genlex token Stream t gt expression lt fun gt H H H HH HOF FH FH FH OH FH OF OF OF FH OF w 5 a val parse_more_adds expression gt Genlex token Stream t gt expression lt fun gt val parse_mult Genlex token Stream t gt expression lt fun gt val parse_more_mults expression gt Genlex token
390. sed maz returns a fresh custom block with room for size bytes of user data and whose associated operations are given by ops a pointer toa struct custom_operations usually statically allocated as a C global variable 216 The two parameters used and maz are used to control the speed of garbage collection when the finalized object contains pointers to out of heap resources Generally speaking the Caml incre mental major collector adjusts its speed relative to the allocation rate of the program The faster the program allocates the harder the GC works in order to reclaim quickly unreachable blocks and avoid having large amount of floating garbage unreferenced objects that the GC has not yet collected Normally the allocation rate is measured by counting the in heap size of allocated blocks However it often happens that finalized objects contain pointers to out of heap memory blocks and other resources such as file descriptors X Windows bitmaps etc For those blocks the in heap size of blocks is not a good measure of the quantity of resources allocated by the program The two arguments used and maz give the GC an idea of how much out of heap resources are consumed by the finalized block being allocated you give the amount of resources allocated to this object as parameter used and the maximum amount that you want to see in floating garbage as parameter maz The units are arbitrary the GC cares only about the ratio used maz F
391. semantic actions in the style of yacc Assuming the input file is grammar mly executing ocamlyacc options grammar mly produces Caml code for a parser in the file grammar m1 and its interface in file grammar mli The generated module defines one parsing function per entry point in the grammar These functions have the same names as the entry points Parsing functions take as arguments a lexical analyzer a function from lexer buffers to tokens and a lexer buffer and return the semantic attribute of the corresponding entry point Lexical analyzer functions are usually generated from a lexer specification by the ocamllex program Lexer buffers are an abstract data type implemented in the standard library module Lexing Tokens are values from the concrete type token defined in the interface file grammar mli produced by ocamlyacc 12 4 Syntax of grammar definitions Grammar definitions have the following format i header ht declarations Ah rules Ah trailer Comments are enclosed between and as in C in the declarations and rules sections and between and as in Caml in the header and trailer sections Chapter 12 Lexer and parser generators ocamllex ocamlyacc 161 12 4 1 Header and trailer The header and the trailer sections are Caml code that is copied as is into file grammar m1 Both sections are optional The header goes at the beginning of the output file it usually contains open dire
392. slice of the given three dimensional big array by fixing the first coordinate The integer parameter is the first coordinate of the slice to extract See Genarray slice_left for more details Array3 slice_left_2 applies only to arrays with C layout val slice_right_2 Ca b fortran_layout t gt z int gt a b fortran_layout Array2 t Extract a two dimensional slice of the given three dimensional big array by fixing the last coordinate The integer parameter is the coordinate of the slice to extract See Genarray slice_right for more details Array3 slice_right_2 applies only to arrays with Fortran layout external blit src a b c t gt dst a b c t gt unit Copy the first big array to the second big array See Genarray blit for more details external fill a b c t gt a gt unit Fill the given big array with the given value See Genarray fill for more details val of_array kind a b kind gt layout c layout gt a array array array gt a b c t Build a three dimensional big array initialized from the given array of arrays of arrays val map_file Unix file_descr gt kind a b kind gt layout c layout gt shared bool gt dimt int gt dim2 int gt dim3 int gt a b c t Memory mapping of a file as a three dimensional big array See Genarray map_file for more details end Chapter 28 The bigarray library 369 Coercion
393. specifications consist in the character followed by optional flags and field widths followed by one conversion character The conversion characters and their meanings are d or i convert an integer argument to signed decimal u convert an integer argument to unsigned decimal x convert an integer argument to unsigned hexadecimal using lowercase letters X convert an integer argument to unsigned hexadecimal using uppercase letters o convert an integer argument to unsigned octal s insert a string argument c insert a character argument f convert a floating point argument to decimal notation in the style dddd ddd e or E convert a floating point argument to decimal notation in the style d ddd e dd mantissa and exponent g or G convert a floating point argument to decimal notation in style f or e E whichever is more compact b convert a boolean argument to the string true or false a user defined printer Takes two arguments and apply the first one to outchan the current output channel and to the second argument The first argument must therefore have type out_channel gt b gt unit and the second b The output produced by the function is therefore inserted in the output of fprintf at the current point t same as Za but takes only one argument with type out_channel gt unit and apply it to outchan take no argument and output one character Refer to the C library printf function for the meaning
394. ss bad_functional_point int gt object val x int method get_x int method move int gt functional_point end let p new functional_point 7 val p functional_point lt obj gt p get_x int 7 p move 3 get_x int 10 p get_x int 7 While objects of either class will behave the same objects of their subclasses will be different In a subclass of the latter the method move will keep returning an object of the parent class On the contrary in a subclass of the former the method move will return an object of the subclass Functional update is often used in conjunction with binary methods as illustrated in section 5 2 1 3 12 Cloning objects Objects can also be cloned whether they are functional or imperative The library function 00 copy makes a shallow copy of an object That is it returns an object that is equal to the previous one The instance variables have been copied but their contents are shared Assigning a new value to an 52 instance variable of the copy using a method call will not affect instance variables of the original and conversely A deeper assignment for example if the instance variable if a reference cell will of course affect both the original and the copy The type of 0o copy is the following Oo copy gt as a gt a lt fun gt The keyword as in that type binds the type variable a to the object type lt gt Theref
395. ssumes a working knowledge of lex and yacc while it describes the input syntax for ocamllex and ocamlyacc and the main differences with lex and yacc it does not explain the basics of writing a lexer or parser description in lex and yacc Readers unfamiliar with lex and yacc are referred to Compilers principles techniques and tools by Aho Sethi and Ullman Addison Wesley 1986 or Lex amp Yacc by Levine Mason and Brown O Reilly 1992 12 1 Overview of ocamllex The ocamllex command produces a lexical analyzer from a set of regular expressions with attached semantic actions in the style of lex Assuming the input file is lerer m11 executing ocamllex lexer m11 produces Caml code for a lexical analyzer in file Jerer m1 This file defines one lexing function per entry point in the lexer definition These functions have the same names as the entry points Lexing functions take as argument a lexer buffer and return the semantic attribute of the corresponding entry point Lexer buffers are an abstract data type implemented in the standard library module Lexing The functions Lexing from_channel Lexing from_string and Lexing from_function create lexer buffers that read from an input channel a character string or any reading function respec tively See the description of module Lexing in chapter 18 When used in conjunction with a parser generated by ocamlyacc the semantic actions compute a value belonging to the type to
396. stom runtime system The bytecode is appended to the end of the custom runtime system so that it will be automatically executed when the output file custom runtime bytecode is launched To link in custom runtime mode execute the ocamlc command with e the custom option e the names of the desired Caml object files cmo and cma files e the names of the C object files and libraries o and a files that implement the required primitives Under Unix and Windows a library named libname a residing in one of the standard library directories can also be specified as cclib lname If you are using the native code compiler ocamlopt the custom flag is not needed as the final linking phase of ocamlopt always builds a standalone executable To build a mixed Caml C executable execute the ocamlopt command with e the names of the desired Caml native object files cmx and cmxa files e the names of the C object files and libraries o and a files that implement the required primitives Starting with OCaml 3 00 it is possible to record the custom option as well as the names of C libraries in a Caml library file cma or cmxa For instance consider a Caml library mylib cma built from the Caml object files a cmo and b cmo which reference C code in libmylib a If the library is built as follows ocamlc o mylib cma custom a cmo b cmo cclib lmylib Chapter 17 Interfacing C with Objective Caml 197 users of the library c
397. suspend input and TCION transmits a START character to restart input val setsid unit gt int Put the calling process in a new session and detach it from its controlling terminal Chapter 20 The unix library Unix system calls MacOS 317 Under MacOS the Unix library is only available in the toplevel application not in MPW tools Below is a list of the functions that are not implemented or only partially implemented under MacOS Functions not mentioned are fully implemented and behave as described previously in this chapter Functions Comment chown fchown chroot environment putenv execv execve execvp execvpe fork getegid geteuid getgid getuid getgrnam getgrgid getlogin getpid getppid getpwnam getpwuid kill link mkfifo nice setgid setuid times umask wait waitpid establish_server terminal functions tc not implemented not implemented not implemented not implemented not implemented use threads always return 1 not implemented returns the user name as set in the Internet con trol panel returns the low order 31 bits of the PSN not implemented not implemented not implemented not implemented not implemented not implemented not implemented only the process user time is returned not implemented not implemented not implemented not implemented use threads not implemented 318 Windows Below is a list of the functions that are no
398. t 1 4 Records and variants User defined data structures include records and variants Both are defined with the type declara tion Here we declare a record type to represent rational numbers type ratio num int denum int type ratio num int denum int let add_ratio ri r2 num r1 num r2 denum r2 num r1 denum denum ri denum r2 denum val add_ratio ratio gt ratio gt ratio lt fun gt add_ratio num 1 denum 3 num 2 denum 5 ratio num 11 denum 15 The declaration of a variant type lists all possible shapes for values of that type Each case is identified by a name called a constructor which serves both for constructing values of the variant type and inspecting them by pattern matching Constructor names are capitalized to distinguish them from variable names which must start with a lowercase letter For instance here is a variant type for doing mixed arithmetic integers and floats type number Int of int Float of float Error type number Int of int Float of float Error This declaration expresses that a value of type number is either an integer a floating point number or the constant Error representing the result of an invalid operation e g a division by zero Enumerated types are a special case of variant types where all alternatives are constants Chapter 1 The core language 15 type sign Positive Negative type sign Positiv
399. t b lt fun gt Chapter 1 The core language 19 1 7 Symbolic processing of expressions We finish this introduction with a more complete example representative of the use of Caml for symbolic processing formal manipulations of arithmetic expressions containing variables The following variant type describes the expressions we shall manipulate type expression Const of float Var of string Sum of expression expression e1 e2 Diff of expression expression e1 e2 Prod of expression expression el e2 Quot of expression expression el e2 H H HH H HF OF Ee type expression Const of float Var of string Sum of expression expression Diff of expression expression Prod of expression expression Quot of expression expression We first define a function to evaluate an expression given an environment that maps variable names to their values For simplicity the environment is represented as an association list exception Unbound_variable of string exception Unbound_variable of string let rec eval env exp match exp with Const c gt c Var v gt try List assoc v env with Not_found gt raise Unbound_variable v Sum f g gt eval env f eval env g Diff f g gt eval env f eval env g Prod f g gt eval env f eval env g Quot f g gt eval env f eval env g val eval string float list gt expression
400. t b list List rev_map f 1 gives the same result as List rev List map f 1 but is tail recursive and more efficient val fold_left f a gt b gt a gt init a gt b list gt a List fold_left f a b1 bn isf f a b1 b2 bn val fold_right f a gt b gt b gt a list gt init b gt b List fold_right f a1 an bisf a1 f a2 f an b Not tail recursive Iterators on two lists val iter2 f a gt b gt unit gt a list gt b list gt unit List iter2 f a1 an b1 bn calls in turn f al b1 f an bn Raise Invalid_argument if the two lists have different lengths val map2 f a gt b gt c gt a list gt b list gt c list List map2 f al an b1 bn is f a1 b1 f an bn Raise Invalid_argument if the two lists have different lengths Not tail recursive Chapter 19 The standard library 271 val rev_map2 f a gt b gt c gt a list gt b list gt c list List rev_map2 f 1 gives the same result as List rev List map2 f 1 but is tail recursive and more efficient val fold_left2 f Ca gt b gt c gt a gt init a gt b list gt c list gt a List fold_left2 f a b1 bn cl cn is f f a bi c1 b2 c2 bn cn Raise Invalid_argument if the two lists have different l
401. t Convert the given 32 bit integer type int32 to an integer type int On 32 bit platforms the 32 bit integer is taken modulo 2 i e the high order bit is lost during the conversion On 64 bit platforms the conversion is exact of_float float gt int32 Convert the given floating point number to a 32 bit integer discarding the fractional part truncate towards 0 The result of the conversion is undefined if after truncation the number is outside the range Int32 min_int Int32 max_int to_float int32 gt float Convert the given 32 bit integer to a floating point number of_string string gt int32 Convert the given string to a 32 bit integer The string is read in decimal by default or in hexadecimal octal or binary if the string begins with Ox Oo or Ob respectively Raise Failure int_of_string if the given string is not a valid representation of an integer to_string int32 gt string Return the string representation of its argument in signed decimal format string gt int32 gt string Int32 format fmt n return the string representation of the 32 bit integer n in the format specified by fmt fmt is a Printf style format containing exactly one d i Au 4x 4X or 0 conversion specification See the documentation of the Printf module for more information 19 13 Module Int64 64 bit integers val val val This module provides operations on the type int64 of signed 64 bit integers Unlike the b
402. t gt unit Open a tabulation box val close_tbox unit gt unit Close the most recently opened tabulation box val print_tbreak int gt int gt unit Break hint in a tabulation box print_tbreak spaces offset moves the insertion point to the next tabulation spaces being added to this position Nothing occurs if insertion point is already on a tabulation mark If there is no next tabulation on the line then a newline is printed and the insertion point moves to the first tabulation of the box If a new line is printed offset is added to the current indentation val set_tab unit gt unit Set a tabulation mark at the current insertion point val print_tab unit gt unit print_tab is equivalent to print_tbreak 0 0 Chapter 19 The standard library Ellipsis val set_ellipsis_text string gt unit Set the text of the ellipsis printed when too many boxes are opened a single dot by default val get_ellipsis_text unit gt string Return the text of the ellipsis Redirecting formatter output val set_formatter_out_channel out_channel gt unit Redirect the pretty printer output to the given channel val set_formatter_output_functions out buf string gt pos int gt len int gt unit gt flush unit gt unit gt unit 251 set_formatter_output_functions out flush redirects the pretty printer output to the functions out and flush The out function performs the pretty
403. t int64 Convert the given floating point number to a 64 bit integer discarding the fractional part truncate towards 0 The result of the conversion is undefined if after truncation the number is outside the range Int64 min_int Int64 max_int to_float int64 gt float Convert the given 64 bit integer to a floating point number of_int32 int32 gt int64 Convert the given 32 bit integer type int32 to a 64 bit integer type int64 Chapter 19 The standard library 267 val to_int32 int64 gt int32 Convert the given 64 bit integer type int64 to a 32 bit integer type int32 The 64 bit integer is taken modulo 2 i e the top 32 bits are lost during the conversion val of_nativeint nativeint gt int64 Convert the given native integer type nativeint to a 64 bit integer type int64 val to_nativeint int64 gt nativeint Convert the given 64 bit integer type int64 to a native integer On 32 bit platforms the 64 bit integer is taken modulo 2 On 64 bit platforms the conversion is exact val of_string string gt int64 Convert the given string to a 64 bit integer The string is read in decimal by default or in hexadecimal octal or binary if the string begins with Ox 0o or Ob respectively Raise Failure int_of_string if the given string is not a valid representation of an integer val to_string int64 gt string Return the string representation of its argument in decimal val format string
404. t left most coordinates Genarray slice_left a li1 iMI returns the slice of a obtained by setting the first M coordinates to i1 iM If a has N dimensions the slice has dimension N M and the element at coordinates j1 j N M in the slice is identical to the element at coordinates i1 iM j1 j N M in the original array a No copying of elements is involved the slice and the original array share the same storage space Genarray slice_left applies only to big arrays in C layout Raise Invalid_arg if M gt N or if li1 iMl is outside the bounds of a external slice_right Ca b fortran_layout t gt int array gt a b fortran_layout t Extract a sub array of lower dimension from the given big array by fixing one or several of the last right most coordinates Genarray slice_right a il iM returns the slice of a obtained by setting the last M coordinates to i1 iM If a has N dimensions the slice has dimension N M and the element at coordinates Clj1 j N M in the slice is identical to the element at coordinates Clji jQN M it iMI in the original array a No copying of elements is involved the slice and the original array share the same storage space Genarray slice_right applies only to big arrays in Fortran layout Raise Invalid_arg if M gt N or if li1 iM is outside the bounds of a Chapter 28 The bigarray
405. t string Return the string representation of an integer in decimal val int_of_string string gt int Convert the given string to an integer The string is read in decimal by default or in hexadecimal octal or binary if the string begins with Ox Oo or Ob respectively Raise Failure int_of_string if the given string is not a valid representation of an integer val string_of_float float gt string Return the string representation of a floating point number val float_of_string string gt float Convert the given string to a float The result is unspecified if the given string is not a valid representation of a float 230 Pair operations val fst a b gt a Return the first component of a pair val snd a b gt b Return the second component of a pair List operations More list operations are provided in module List val a list gt a list gt a list List concatenation Input output type in_channel type out_channel The types of input channels and output channels val stdin in_channel val stdout out_channel val stderr out_channel The standard input standard output and standard error output for the process Output functions on standard output val print_char char gt unit Print a character on standard output val print_string string gt unit Print a string on standard output val print_int int gt unit Print an integer in decimal on sta
406. t val repr s method get n String get n method set n c String set nc method print print_string repr method copy lt repr String copy repr gt method sub start len lt repr String sub s start len gt end class better_string string gt object a val repr string method copy a method get string gt int gt char method print unit method set string gt int gt char gt unit method sub int gt int gt a end Chapter 5 Advanced examples with classes and modules 75 As shown in the inferred type the methods copy and sub now return objects of the same type as the one of the class Another difficulty is the implementation of the method concat In order to concatenate a string with another string of the same class one must be able to access the instance variable externally Thus a method repr returning s must be defined Here is the correct definition of strings class ostring s object self mytype val repr s method repr repr method get n String get n method set n c String set nc method print print_string repr method copy lt repr String copy repr gt method sub start len lt repr String sub s start len gt method concat t mytype lt repr repr t repr gt end class ostring string gt object a val repr string method concat a gt a method copy a met
407. t a date and time specified by the tm argument into a time in seconds as returned by time Also return a normalized copy of the given tm record with the tm_wday tm_yday and tm_isdst fields recomputed from the other fields The tm argument is interpreted in the local time zone alarm int gt int Schedule a SIGALRM signals after the given number of seconds 308 val sleep int gt unit Stop execution for the given number of seconds val times unit gt process_times Return the execution times of the process val utimes string gt access float gt modif float gt unit Set the last access time second arg and last modification time third arg for a file Times are expressed in seconds from 00 00 00 GMT Jan 1 1970 type interval_timer ITIMER_REAL ITIMER_VIRTUAL ITIMER_PROF The three kinds of interval timers ITIMER_REAL decrements in real time and sends the signal SIGALRM when expired ITIMER_VIRTUAL decrements in process virtual time and sends SIGVTALRM when expired ITIMER_PROF for profiling decrements both when the process is running and when the system is running on behalf of the process it sends SIGPROF when expired type interval_timer_status it_interval float Period it_value float Current value of the timer The type describing the status of an interval timer val getitimer interval_timer gt interval_timer_status Return the current status of the given interval timer
408. t component expr is evaluated first The second component exprs is not evaluated if the first component evaluates to true Hence the expression expr expr behaves exactly as if expr then true else expro The boolean operator amp is synonymous for amp amp The boolean operator or is synonymous for Loops The expression while expr do expr done repeatedly evaluates expr while expr evaluates to true The loop condition expr is evaluated and tested at the beginning of each iteration The whole while done expression evaluates to the unit value The expression for name expr to expr do expr done first evaluates the expressions expr and expr the boundaries into integer values n and p Then the loop body expr is repeatedly evaluated in an environment where name is successively bound to the values n n 1 p 1 p The loop body is never evaluated if n gt p The expression for name expr downto expr do expr3 done evaluates similarly except that name is successively bound to the values n n 1 p 1 p The loop body is never evaluated ifn lt p In both cases the whole for expression evaluates to the unit value Exception handling The expression try expr with pattern gt expr pattern gt expr evaluates the expression expr and returns its value if the evaluation of expr does not raise any exception If the evaluation of expr raises an exception the exception value is matched a
409. t definition of a method is kept the redefinition in a subclass of a method that was visible in the parent class overrides the definition in the parent class Previous definitions of a method can be reused by binding the related ancestor Below super is bound to the ancestor printable_point The name super is not actually a variable and can only be used to select a method as in super print class printable_colored_point y c object self val c c method color c inherit printable_point y as super method print print_string super print print_string print_string self color print_string end class printable_colored_point int gt string gt object val c string val mutable x int method color string method get_x int method move int gt unit method print unit end let p new printable_colored_point 17 red new point at 10 red val p printable_colored_point lt obj gt p print 10 red unit A private method that has been hidden in the parent class is no more visible and is thus not overridden Since initializers are treated as private methods all initializers along the class hierarchy are evaluated in the order they are introduced 3 9 Parameterized classes Reference cells can also be implemented as objects The naive definition fails to typecheck class ref x_init Chapter 3 Objects in Caml 45
410. t implemented or only partially implemented under Windows Functions not mentioned are fully implemented and behave as described previously in this chapter truncate ftruncate lstat fstat link symlink readlink fchmod chown fchown umask set_nonblock clear_nonblock rewinddir mkfifo select lockf kill pause alarm times getitimer setitimer getuid getgid getgid getegid getgroups setuid setgid getpwnam getpwuid getgrnam getgrgid type socket_domain establish_server terminal functions tc Functions Comment fork not implemented use create_process or threads wait not implemented use waitpid waitpid can only wait for a given PID not any child process getppid not implemented meaningless under Windows nice not implemented not implemented not implemented not implemented no links under Windows not implemented not implemented make no sense on a DOS file system not implemented implemented as dummy functions use threads instead of non blocking I O not implemented re open the directory instead not implemented implemented but works only for sockets use threads if you need to wait on other kinds of file descriptors not implemented not implemented no inter process signals in Windows not implemented not implemented always return 1 not implemented not implemented always raise Not_found always raise Not_found the domain PF_UNIX is not supported PF_INET
411. t to do when receiving a signal Signal_default take the default behavior usually abort the program Signal_ignore ignore the signal Signal_handle f call function f giving it the signal number as argument Signal int gt signal_behavior gt signal_behavior Set the behavior of the system on receipt of a given signal The first argument is the signal number Return the behavior previously associated with the signal set_signal int gt signal_behavior gt unit Same as signal but return value is ignored sigabrt int Abnormal termination sigalrm int Timeout sigfpe int Arithmetic exception sighup int Hangup on controlling terminal sigill int Invalid hardware instruction sigint int Interactive interrupt ctr1l C sigkill int Termination cannot be ignored Sigpipe int Broken pipe sigquit int Interactive termination sigsegv int Invalid memory reference sigterm int Termination sigusri int Application defined signal 1 sigusr2 int Application defined signal 2 sigchld int Child process terminated sigcont int Continue sigstop int Stop sigtstp int Interactive stop Sigttin int Terminal read from background process Sigttou int Terminal write from background process sigvtalrm int Timeout in virtual time Sigprof int Profiling interrupt Signal numbers for the standard POSIX signa
412. t to the file named new File permissions and ownership type access_permission R_OK Read permission W_OK Write permission X_OK Execution permission F_OK File exists Flags for the access call val chmod string gt perm file_perm gt unit Change the permissions of the named file val fchmod file_descr gt perm file_perm gt unit Change the permissions of an opened file val chown string gt uid int gt gid int gt unit Change the owner uid and owner gid of the named file val fchown file_descr gt uid int gt gid int gt unit Change the owner uid and owner gid of an opened file val umask int gt int Set the process creation mask and return the previous mask val access string gt perm access_permission list gt unit Check that the process has the given permissions over the named file Raise Unix_error otherwise Chapter 20 The unix library Unix system calls 303 Operations on file descriptors val dup file_descr gt file_descr Return a new file descriptor referencing the same file as the given descriptor val dup2 src file_descr gt dst file_descr gt unit dup2 fdi fd2 duplicates fd1 to fd2 closing fd2 if already opened val set_nonblock file_descr gt unit val clear_nonblock file_descr gt unit Set or clear the non blocking flag on the given descriptor When the non blocking flag is set reading on a descriptor on which there is t
413. t_found if there is no value that satisfies p in the list 1 val filter f a gt bool gt a list gt a list val find_all f a gt bool gt a list gt a list filter p 1 returns all the elements of the list 1 that satisfies the predicate p The order of the elements in the input list is preserved find_all is another name for filter val partition f a gt bool gt a list gt a list a list partition p 1 returns a pair of lists 11 12 where 11 is the list of all the elements of 1 that satisfy the predicate p and 12 is the list of all the elements of 1 that do not satisfy p The order of the elements in the input list is preserved Association lists val assoc a gt a b list gt b assoc a 1 returns the value associated with key a in the list of pairs 1 That is assoc a a b bif a b is the leftmost binding of a in list 1 Raise Not_found if there is no value associated with a in the list 1 val assq a gt a b list gt b Same as assoc but uses physical equality instead of structural equality to compare keys val mem_assoc a gt a b list gt bool Same as assoc but simply return true if a binding exists and false if no bindings exist for the given key val mem_assq a gt a b list gt bool Same as mem_assoc but uses physical equality instead of structural equality to compare keys
414. tag t The size of the block can be greater than Max_young_wosize It can also be smaller but in this case it is more efficient to call alloc_small instead of alloc_shr If this block is a structured block i e if t lt No_scan_tag then the fields of the block initially containing garbage must be initialized with legal values using the initialize function described below before the next allocation 17 4 5 Raising exceptions Two functions are provided to raise two standard exceptions e failwith s where s is a null terminated C string with type char raises exception Failure with argument s e invalid_argument s where s is a null terminated C string with type char raises ex ception Invalid_argument with argument s Raising arbitrary exceptions from C is more delicate the exception identifier is dynamically allocated by the Caml program and therefore must be communicated to the C function using the registration facility described below in section 17 7 3 Once the exception identifier is recovered in C the following functions actually raise the exception e raise_constant id raises the exception id with no argument e raise_with_arg id v raises the exception id with the Caml value v as argument e raise_with_string id s where s is a null terminated C string raises the exception id with a copy of the C string s as argument 17 5 Living in harmony with the garbage collector Unused blocks in the heap are aut
415. tecode interpreter ocamlrun 8 1 Overview of the compiler The ocamlc command has a command line interface similar to the one of most C compilers It accepts several types of arguments e Arguments ending in mli are taken to be source files for compilation unit interfaces Inter faces specify the names exported by compilation units they declare value names with their types define public data types declare abstract data types and so on From the file z m1i the ocamlc compiler produces a compiled interface in the file x cmi e Arguments ending in ml are taken to be source files for compilation unit implementations Implementations provide definitions for the names exported by the unit and also contain expressions to be evaluated for their side effects From the file x ml the ocamlc compiler produces compiled object bytecode in the file x cmo If the interface file x mli exists the implementation x m1 is checked against the corresponding compiled interface x cmi which is assumed to exist If no interface z mli is provided the compilation of x ml produces a compiled interface file x cmi in addition to the compiled object code file z cmo The file x cmi produced corresponds to an interface that exports everything that is defined in the implementation z m1 e Arguments ending in cmo are taken to be compiled object bytecode These files are linked together along with the object files obtained by compiling m1 arguments if any and the
416. ted frame that is the frame that called the selected frame An argument says how many frames to go up down count Select and display the stack frame just below the selected frame that is the frame that was called by the selected frame An argument says how many frames to go down 15 7 Examining variable values The debugger can print the current value of simple expressions The expressions can involve program variables all the identifiers that are in scope at the selected program point can be accessed Expressions that can be printed are a subset of Objective Caml expressions as described by the following grammar expr lowercase ident capitalized ident lowercase ident integer expr lowercase ident expr integer expr integer expr expr The first two cases refer to a value identifier either unqualified or qualified by the path to the structure that define it refers to the result just computed typically the value of a function 182 application and is valid only if the selected event is an after event typically a function appli cation integer refer to a previously printed value The remaining four forms select part of an expression respectively a record field an array element a string element and the current contents of a reference print variables Print the values of the given variables print can be abbreviated as p display variables Same as print but li
417. ted variant type or record type an equation a representation This case combines the previous two the representation of the type is made visible to all users and no fresh type is generated Exception specification The specification exception constr decl in a signature requires the matching structure to provide an exception with the name and arguments specified in the definition and makes the exception available to all users of the structure Class specifications A specification of one or several classes in a signature is written class class spec and class spec and consists of a sequence of mutually recursive definitions of class names Class specifications are described more precisely in section 6 9 4 120 Class type specifications A specification of one or several classe types in a signature is written class type classtype def and classtype de and consists of a sequence of mutually recursive definitions of class type names Class type specifications are described more precisely in section 6 9 5 Module specifications A specification of a module component in a signature is written module module name module type where module name is the name of the module component and module type its expected type Modules can be nested arbitrarily in particular functors can appear as components of structures and functor types as components of signatures For specifying a module component that is a functor one may write module module n
418. th methods and their associated types are described by method type method type and possibly some other methods represented by the ellipsis This ellipsis actually is a special kind of type variable also called row variable in the literature that stands for any number of extra method types types The type class path is a special kind of abbreviation This abbreviation unifies with the type of any object belonging to a subclass of class class path It is handled in a special way as it usually hides a type variable an ellipsis representing the methods that may be added in a subclass In particular it vanishes when the ellipsis gets instantiated Each type expression class path defines a new type variable so type class path gt class path is usually not the same as type class path as ident gt ident types can also be used to abbreviate variant types Similarly they express the presence of a row variable allowing further refinement of the type Precisely if t has been defined as the type tag t tag tn then t is the type lt tag t tag tn J and t gt tag tag is the type lt tag t tag tn gt tag tag l Variant and record types There are no type expressions describing defined variant types nor record types since those are always named i e defined before use and referred to by name Type definitions are described in section
419. thdraw x if x leq balance then balance lt balance plus neg x x else zero end class account object val mutable balance Euro c method balance Euro c 67 68 method deposit Euro c gt unit method withdraw Euro c gt Euro c end let c new account in c deposit euro 100 c withdraw euro 50 Euro c lt obj gt We now refine this definition with a method to compute interest class account_with_interests object self inherit account method private interest self deposit self balance times 0 03 end class account_with_interests object val mutable balance Euro c method balance Euro c method deposit Euro c gt unit method private interest unit method withdraw Euro c gt Euro c end We make the method interest private since clearly it should not be called freely from the outside Here it is only made accessible to subclasses that will manage monthly or yearly updates of the account We should soon fix a bug in the current definition the deposit method can be used for with drawing money by depositing negative amounts We can fix this directly class safe_account object inherit account method deposit x if zero leq x then balance lt balance plus x end class safe_account object val mutable balance Euro c method balance Euro c method deposit Euro c gt unit method withdraw Euro c gt Euro c end H
420. the class a stack but to the argument that will be passed to the method fold The intuition is that method fold should be polymorphic i e of type All Ca b gt 2a gt b gt b gt b which is not currently possible One possibility would be to make b an extra parameter of class stack class a b stack2 object inherit a stack method fold f x b List fold_left f x 1 end class a b stack2 object val mutable 1 a list method clear unit method fold b gt a gt b gt b gt b method length int method pop a method push a gt unit end However the method fold of a given object can only be applied to functions that all have the same type let s new stack2 val s _a _b stack2 lt obj gt s fold 0 int 0 S33 int int stack2 lt obj gt Chapter 5 Advanced examples with classes and modules 77 The best solution would be to make method fold polymorphic However OCaml does not currently allow methods to be polymorphic Thus the current solution is to leave the function fold outside of the class class a stack3 object inherit a stack method iter f List iter f a gt unit 1 end class a stack3 object val mutable 1 a list method clear unit method iter a gt unit gt unit method length int method pop a method
421. the linking phase of the compilation Source code files are turned into compiled files but no executable file is produced This option is useful to compile modules separately cc ccomp Use ccomp as the C linker called to build the final executable and as the C compiler for compiling c source files cclib llibname Pass the Llibname option to the linker This causes the given C library to be linked with the program Chapter 11 Native code compilation ocamlopt 153 ccopt option Pass the given option to the C compiler and linker For instance ccopt Ldir causes the C linker to search for C libraries in directory dir compact Optimize the produced code for space rather than for time This results in slightly smaller but slightly slower programs The default is to optimize for speed i Cause the compiler to print all defined names with their inferred types or their definitions when compiling an implementation m1 file This can be useful to check the types inferred by the compiler Also since the output follows the syntax of interfaces it can help in writing an explicit interface mli file for a file just redirect the standard output of the compiler to a mli file and edit that file to remove all declarations of unexported names I directory Add the given directory to the list of directories searched for compiled interface files cmi and compiled object code files cmx By default the current directory is searche
422. the shell to choose it in the Editor The executed subshell is given the current load path File use a source file or load a bytecode file You may also import the browser s path into the subprocess History M p and M n browse up and down Signal C c interrupts and you can also kill the subprocess 174 Chapter 15 The debugger ocamldebug This chapter describes the Objective Caml source level replay debugger ocamldebug Unix The debugger is available on Unix systems that provides BSD sockets Windows The debugger is not available MacOS The debugger is not available 15 1 Compiling for debugging Before the debugger can be used the program must be compiled and linked with the g option all cmo and cma files that are part of the program should have been created with ocamlc g and they must be linked together with ocamlc g Compiling with g entails no penalty on the running time of programs object files and bytecode executable files are bigger and take longer to produce but the executable files run at exactly the same speed as if they had been compiled without g 15 2 Invocation 15 2 1 Starting the debugger The Objective Caml debugger is invoked by running the program ocamldebug with the name of the bytecode executable file as first argument ocamldebug options program arguments The arguments following program are optional and are passed as command line arguments to the program being debugged
423. the signature To avoid combinatorial explosion of the search space optional arguments in the actual type are ignored in the actual if 1 there are too many of them and 2 they do not appear explicitly in the pattern Chapter 14 The browser editor ocamlbrowser 173 14 4 File editor You can edit files with it if you re not yet used to emacs Otherwise you can use it as a browser making occasional corrections The Edit menu contains commands for jump C g search C s and sending the current phrase or selection if some text is selected to a sub shell M x For this last option you may choose the shell via a dialog Essential functions are in the Compiler menu Preferences opens a dialog to set internals of the editor and type checker Lex adds colors according to lexical categories Typecheck verifies typing and memorizes to let one see an expression s type by double clicking on it This is also valid for interfaces If an error occurs the part of the interface preceding the error is computed After typechecking pressing the right button pops up a menu giving the type of the pointed expression and eventually allowing to follow some links Clear errors dismisses type checker error messages and warnings Signature shows the signature of the current file after type checking 14 5 Shell When you create a shell a dialog is presented to you letting you choose which command you want to run and the title of
424. ties of classes class type class body type label typexpr gt class type class body type object typexpr class field spec end class path typexpr typexpr class path class field spec inherit class type val mutable inst var name typexpr method private method name typexpr method private virtual method name typexpr constraint typexpr typexpr Simple class expressions The expression class path is equivalent to the class type bound to the name class path Similarly the expression typexpr typexpr class path is equivalent to the parametric class type bound to the name class path in which type parameters have been instanciated to respectively typexpr typexpr Class function type The class type expression typexpr gt class type is the type of class functions functions from values to classes that take as argument a value of type typexpr and return as result a class of type class type Class body type The class type expression object typexpr class field spec end is the type of a class body It specifies its instance variables and methods In this type typexpr is match agains self type therefore provinding a binding for self type A class body will match a class body type if it provides definitions for all the components specified in the class type and these definitions meet the type requirements given in the class type Furthermore all methods either virtual or p
425. ting system provides POSIX 1003 1c compliant threads you can select an alternate implementation when configuring Objective Caml use the with pthread option to configure which also supports native code programs Programs that use this alternate implementation of the threads library must be linked as follows ocamlc thread other options threads cma other files ocamlopt thread other options threads cmxa other files Depending on the operating system extra system libraries can be necessary For instance under Solaris 2 5 add cclib lposix4 at the end of the command line Windows Programs that use the threads library must be linked as follows ocamlc thread other options threads cma other files 331 332 All object files on the command line must also have been compiled with the thread option which selects a special thread safe version of the standard library see chapter 8 23 1 Module Thread lightweight threads type t The type of thread handles Thread creation and termination val create a gt b gt a gt t Thread create funct arg creates a new thread of control in which the function application funct arg is executed concurrently with the other threads of the program The application of Thread create returns the handle of the newly created thread The new thread terminates when the application funct arg returns either normally or by raising an uncaught exception In the latter case the exception is
426. tion Initially on get_approx_printing unit gt bool set_approx_printing bool gt unit Get or set the flag approx_printing When on rational numbers are printed as a decimal approximation When off rational numbers are printed as a fraction Initially off get_floating_ precision unit gt int set_floating precision int gt unit Get or set the parameter floating_precision This parameter is the number of digits displayed when approx_printing is on Initially 12 324 Chapter 22 The str library regular expressions and string processing The str library provides high level string processing functions some based on regular expressions It is intended to support the kind of file processing that is usually performed with scripting languages such as awk perl or sed Programs that use the str library must be linked as follows ocamlc other options str cma other files ocamlopt other options str cmxa other files For interactive use of the str library do ocamlmktop o mytop str cma mytop 22 1 Module Str regular expressions and high level string processing Regular expressions type regexp The type of compiled regular expressions val regexp string gt regexp Compile a regular expression The syntax for regular expressions is the same as in Gnu Emacs The special characters are The following constructs are recognized matches any character except newline postfix matches the previous e
427. tion o incorporating the C object files and libraries given on the command line This custom runtime system can be used later to execute bytecode executables produced with the ocamlc use runtime runtime name option See section 17 1 4 for more information noassert Turn assertion checking off assertions are not compiled This flag has no effect when linking already compiled files noautolink When linking cma libraries ignore custom cclib and ccopt options potentially con tained in the libraries if these options were given when building the libraries This can be useful if a library contains incorrect specifications of C libraries or C options in this case during linking set noautolink and pass the correct C libraries and options on the command line o exec file Specify the name of the output file produced by the linker The default output name is a out in keeping with the Unix tradition If the a option is given specify the name of the library produced If the output obj option is given specify the name of the output file produced output obj Cause the linker to produce a C object file instead of a bytecode executable file This is useful to wrap Caml code as a C library callable from any C program See chapter 17 section 17 7 5 The name of the output object file is camlprog o by default it can be set with the o option pp command Cause the compiler to call the given command as a preprocessor for each source fil
428. tion for licensing information The Objective Caml system can be freely redistributed More precisely INRIA grants any user of the Objective Caml system the right to reproduce it provided that the copies are distributed under the conditions given in the LICENSE file The present documentation is distributed under the same conditions 8 Foreword Availability The complete Objective Caml distribution resides on the machine ftp inria fr The distribution files can be transferred by anonymous FTP Host ftp inria fr Internet address 192 93 2 54 Login name anonymous Password your e mail address Directory lang caml light Files see the index in file README More information on the Caml family of languages is also available on the World Wide Web http caml inria fr Part I An introduction to Objective Caml Chapter 1 The core language This part of the manual is a tutorial introduction to the Objective Caml language A good famil iarity with programming in a conventional languages say Pascal or C is assumed but no prior exposure to functional languages is required The present chapter introduces the core language Chapter 3 deals with the object oriented features and chapter 4 with the module system 1 1 Basics For this overview of Caml we use the interactive system which is started by running ocam1 from the Unix shell or by launching the OCamlwin exe application under Windows This tutorial is presented as the tr
429. tions from structures to structures They are used to express parameterized structures a structure A parameterized by a structure B is simply a functor F with a formal parameter B along with the expected signature for B which returns the actual structure A itself The functor F can then be applied to one or several implementations B1 Bn of B yielding the corresponding structures A n For instance here is a structure implementing sets as sorted lists parameterized by a structure providing the type of the set elements and an ordering function over this type used to keep the sets sorted type comparison Less Equal Greater type comparison Less Equal Greater module type ORDERED_TYPE sig type t val cmp t gt t gt comparison end module type ORDERED_TYPE sig type t val cmp t gt t gt comparison end module Set functor Elt ORDERED_TYPE gt a N struct type element Elt t type set element list let empty let rec add x s match s with gt x hd tl gt match Elt cmp x hd with Equal gt s x is already in s Less gt X ig x is smaller than all elements of s Greater gt hd add x tl let rec member x s match s with H HHH HHH HH HH HHH HH HH H OH OF gt false hd tl gt match Elt cmp x hd with Equal gt true x belongs to s Less gt false x is smaller than all elements of s Greate
430. to catch exceptions escaping the Caml function it can use the func tions callback_exn callback2_exn callback3_exn callbackN_exn These functions take the 210 same arguments as their non _exn counterparts but catch escaping exceptions and return them to the C code The return value v of the callback _exn functions must be tested with the macro Is_exception_result v If the macro returns false no exception occured and v is the value returned by the Caml function If Is_exception_result v returns true an exception escaped and its value the exception descriptor can be recovered using Extract_exception v 17 7 2 Registering Caml closures for use in C functions The main difficulty with the callback functions described above is obtaining a closure to the Caml function to be called For this purpose Objective Caml provides a simple registration mechanism by which Caml code can register Caml functions under some global name and then C code can retrieve the corresponding closure by this global name On the Caml side registration is performed by evaluating Callback register n v Here n is the global name an arbitrary string and v the Caml value For instance let f x print_string f is applied to print_int n print_newline let _ Callback register test function f On the C side a pointer to the value registered under name n is obtained by calling caml_named_value n The returned pointer must then be dereferenced
431. tors and non closed constructions The constructions with higher precedence come first For infix and prefix symbols we write to mean any symbol starting with Construction or operator Associativity prefix symbol pad alk function application left constructor application prefix KL right paa Vives mod left Fan Sof left os right Cas right comparisons lt etc all other infix symbols left not amp amp amp left or l left lt right if right let match fun function try Chapter 6 The Objective Caml language 101 6 7 1 Basic expressions Constants Expressions consisting in a constant evaluate to this constant Value paths Expressions consisting in an access path evaluate to the value bound to this path in the current eval uation environment The path can be either a value name or an access path to a value component of a module Parenthesized expressions The expressions expr and begin expr end have the same value as expr Both constructs are semantically equivalent but it is good style to use begin end inside control structures if then begin end else begin end and for the other grouping situations Parenthesized expressions can contain a type constraint as in expr type This constraint forces the type of expr to be compatible with type Parenthesized expressions can also contain coercions e
432. tr_when gt terminal_io gt unit Set the status of the terminal referred to by the given file descriptor The second argument indicates when the status change takes place immediately TCSANOW when all pending output has been transmitted TCSADRAIN or after flushing all input that has been received but not read TCSAFLUSH TCSADRAIN is recommended when changing the output parameters TCSAFLUSH when changing the input parameters 316 val tcsendbreak file_descr gt duration int gt unit Send a break condition on the given file descriptor The second argument is the duration of the break in 0 1s units 0 means standard duration 0 25s val tcdrain file_descr gt unit Waits until all output written on the given file descriptor has been transmitted type flush_queue TCIFLUSH TCOFLUSH TCIOFLUSH val tcflush file_descr gt mode flush_queue gt unit Discard data written on the given file descriptor but not yet transmitted or data received but not yet read depending on the second argument TCIFLUSH flushes data received but not read TCOFLUSH flushes data written but not transmitted and TCIOFLUSH flushes both type flow_action TCOOFF TCOON TCIOFF TCION val tcflow file_descr gt mode flow_action gt unit Suspend or restart reception or transmission of data on the given file descriptor depending on the second argument TCOOFF suspends output TCOON restarts output TCIOFF transmits a STOP character to
433. tual get_x int method get_offset self get_x x_init method virtual move int gt unit end class virtual abstract_point int gt object val mutable x int method get_offset int method virtual get_x int method virtual move int gt unit end class point x_init object inherit abstract_point x_init method get_x x method move d x lt x d end class point int gt object val mutable x int method get_offset int method get_x int method move int gt unit end HOH FH 3 5 Private methods Private methods are methods that do not appear in object interfaces from other methods of the same object class restricted_point x_init object self val mutable x x_init method private move d x lt x d method bump self move 1 end class restricted_point int gt object val mutable x int method get_x x method bump unit method get_x int method private move int gt unit end let p new restricted_point 0 val p restricted_point lt obj gt p move 10 This expression has type restricted_point It has no method move p bump unit They can only be invoked Private methods are inherited they are by default visible in subclasses unless they are hidden by signature matching as described below Private methods can be made public in a subclass Chapter 3 Objects in Caml 41 class point_again
434. ublic present in the class body must also be present in the class type on the other hand some instance variables and concrete private methods may be omitted A virtual method will match a concrete method thus allowing to forget its implementation An immutable instance variable will match a mutable instance variable Chapter 6 The Objective Caml language 113 Inheritance The inheritance construct inherit class type allows to include methods and instance variables from other classes types The instance variable and method types from this class type are added into the current class type Instance variable specification A specification of an instance variable is written val mutable inst var name typexpr where inst var name is the name of the instance variable and typexpr its expected type The flag mutable indicates whether this instance variable can be physically modified An instance variable specification will hide any previous specification of an instance variable of the same name Method specification A specification of an method is written method private method name typexpr where method name is the name of the method and typexpr its expected type The flag private indicates whether the method can be accessed from outside the class Several specification for the same method must have compatible types Virtual method specification Virtual method specification is written method private virtual method name typexpr where
435. uced by one of the Marshal to_ functions and reconstructs and returns the corresponding value from_string string gt pos int gt a Marshal from_string buff ofs unmarshals a structured value like Marshal from_channel does except that the byte representation is not read from a channel but taken from the string buff starting at position ofs header_size int data_size string gt pos int gt int total_size string gt pos int gt int The bytes representing a marshaled value are composed of a fixed size header and a variable sized data part whose size can be determined from the header Marshal header_size is the size in characters of the header Marshal data_size buff ofs is the size in characters of the data part assuming a valid header is stored in buff starting at position ofs Finally Marshal total_size buff ofs is the total size in characters of the marshaled value Both Marshal data_size and Marshal total_size raise Failure if buff ofs does not contain a valid header To read the byte representation of a marshaled value into a string buffer the program needs to read first Marshal header_size characters into the buffer then determine the length of the remainder of the representation using Marshal data_size make sure the buffer is large enough to hold the remaining data then read it and finally call Marshal from_string to unmarshal the value Chapter 19 The standard library 277 19 19 Module Nativ
436. ugh both set types contain elements of the same type strings both are built upon different orderings of that type and different invariants need to be maintained by the operations being strictly increasing for the standard ordering and for the case insensitive ordering Applying operations from AbstractStringSet to values of type NoCaseStringSet set could give incorrect results or build lists that violate the invariants of NoCaseStringSet 4 5 Modules and separate compilation 66 All examples of modules so far have been given in the context of the interactive system However modules are most useful for large batch compiled programs For these programs it is a practi cal necessity to split the source into several files called compilation units that can be compiled separately thus minimizing recompilation after changes In Objective Caml compilation units are special cases of structures and signatures and the relationship between the units can be explained easily in terms of the module system A compilation unit a comprises two files e the implementation file a m1 which contains a sequence of definitions analogous to the inside of a struct end construct e the interface file a mli which contains a sequence of specifications analogous to the inside of a sig end construct Both files define a structure named A same name as the base name a of the two files with the first letter capitalized as if the following definition
437. uilt in int type the type int64 is guaranteed to be exactly 64 bit wide on all platforms All arithmetic operations over int64 are taken modulo 2 The type int64 is supported on all 64 bit platforms as well as on all 32 bit platforms for which the C compiler supports 64 bit arithmetic On 32 bit platforms without support for 64 bit arithmetic all functions in this module raise an Invalid_argument exception zero int64 one int64 minus_one int64 The 64 bit integers 0 1 1 Chapter 19 The standard library 265 val val val val val val val val val val val val neg int64 gt int64 Unary negation add int64 gt int64 gt int64 Addition sub int64 gt int64 gt int64 Subtraction mul int64 gt int64 gt int64 Multiplication div int64 gt int64 gt int64 Integer division Raise Division_by_zero if the second argument is zero rem int64 gt int64 gt int64 Integer remainder If x gt 0 and y gt 0 the result of Int64 rem x y satisfies the following properties 0 lt Int64 rem x y lt y and x Int64 add Int64 mul Int64 div x y y Int64 rem x y Ify 0 Int64 rem x y raises Division_by_zero If x lt Oor y lt 0 the result of Int64 rem x y is not specified and depends on the platform succ int64 gt int64 Successor Int64 succ x is Int64 add x 1i pred int64 gt int64 Predecessor Int64 pred x is Int64 sub x 1i abs int64 gt i
438. um gt num gt num val mult_num num gt num gt num Multiplication val square_num num gt num Squaring val num gt num gt num val div_num num gt num gt num Division val quo_num num gt num gt num val mod_num num gt num gt num Euclidean division quotient and remainder val num gt num gt num val power_num num gt num gt num Exponentiation val is_integer_num num gt bool Test if a number is an integer val integer_num num gt num val floor_num num gt num val round_num num gt num val ceiling num num gt num Approximate a number by an integer floor_num n returns the largest integer smaller or equal to n ceiling_num n returns the smallest integer bigger or equal to n integer_num n returns the integer closest to n In case of ties rounds towards zero round_num n returns the integer closest to n In case of ties rounds off zero Chapter 21 val val val val val val val val val val val val val val val val val val val val The num library arbitrary precision rational arithmetic sign_num num gt int Return 1 0 or 1 according to the sign of the argument num gt num gt bool lt num gt num gt bool gt num gt num gt bool lt num gt num gt bool gt num gt num gt bool lt gt num gt num gt bool gt num gt bool eq_n
439. um num 1lt_num num le_num num gt_num num ge_num num Usual comparisons between numbers compare_num Return 1 O or 1 if the first argument is less than equal to or greater than the second argument max_num num min_num num Return the greater resp the smaller of the two arguments abs_num num gt num gt bool gt num gt bool gt num gt bool gt num gt bool gt num gt num num gt num gt int gt num Absolute value succ_num num succ nis ntl pred_num num pred nis n 1 incr_num num incr ris r r 1 where r is a reference to a number gt num gt num ref gt unit decr_num num ref gt unit decr ris r r 1 where r is a reference to a number Coercions with strings gt num gt num 321 322 val val val val val val val val val val val val val string_of_num num gt string Convert a number to a string using fractional notation approx_num_fix int gt num gt string approx_num_exp int gt num gt string Approximate a number by a decimal The first argument is the required precision The second argument is the number to approximate approx_fix uses decimal notation the first argument is the number of digits after the decimal point approx_exp uses scientific exponential notation the first argument is the number of digits in the mantissa num_of_string string gt num
440. ument env specifies the environment passed to the program Chapter 20 The unix library Unix system calls 305 val val val val val val val val open_process_in string gt in_channel open_process_out string gt out_channel open_process string gt in_channel out_channel High level pipe and process management These functions run the given command in parallel with the program and return channels connected to the standard input and or the standard output of the command The command is interpreted by the shell bin sh cf system Warning writes on channels are buffered hence be careful to call flush at the right times to ensure correct synchronization open_process_full string gt env string array gt in_channel out_channel in_channel Similar to open_process but the second argument specifies the environment passed to the command The result is a triple of channels connected to the standard output standard input and standard error of the command close_process_in in_channel gt process_status close_process_out out_channel gt process_status close_process in_channel out_channel gt process_status close_process_full in_channel out_channel in_channel gt process_status Close channels opened by open_process_in open_process_out open_process and open_process_full respectively wait for the associated command to terminate and return its termination status Symbolic links val symlink
441. uncated bytecode file The file that ocamlrun is trying to execute is not a valid executable bytecode file Probably it has been truncated or mangled since created Erase and rebuild it Uncaught exception The program being executed contains a stray exception That is it raises an exception at some point and this exception is never caught This causes immediate termination of the program The name of the exception is printed but not its arguments Out of memory The program being executed requires more memory than available Either the program builds excessively large data structures or the program contains too many nested function calls and the stack overflows In some cases your program is perfectly correct it just requires more memory than your machine provides In other cases the out of memory message reveals an error in your program non terminating recursive function allocation of an excessively large array or string attempts to build an infinite list or other data structure To help you diagnose this error run your program with the v option to ocamlrun If it displays lots of Growing stack messages this is probably a looping recursive function If it displays lots of Growing heap messages with the heap size growing slowly this is probably an attempt to construct a data structure with too many infinitely many cells If it displays few Growing heap messages but with a huge increment in th
442. ut the newline character at the end Raise End_of_file if the end of the file is reached at the beginning of line input in_channel gt buf string gt pos int gt len int gt int Read up to len characters from the given channel storing them in string buf starting at character number pos It returns the actual number of characters read between 0 and len inclusive A return value of 0 means that the end of file was reached A return value between 0 and len exclusive means that not all requested len characters were read either because no more characters were available at that time or because the implementation found it convenient to do a partial read input must be called again to read the remaining characters if desired See also Pervasives really_input for reading exactly len characters Exception Invalid_argument input is raised if pos and len do not designate a valid substring of buf really_input in_channel gt buf string gt pos int gt len int gt unit Read len characters from the given channel storing them in string buf starting at character number pos Raise End_of_file if the end of file is reached before len characters have been read Raise Invalid_argument really_input if pos and len do not designate a valid substring of buf Chapter 18 The core library 235 val val val val val val val val input_byte in_channel gt int Same as input_char but return the 8 bit integer repr
443. utput_value and input_value as well as the functions from the Marshal module Element kinds type type type type type type type type type type float32_elt float64_elt int8_signed_elt int8_unsigned_elt int16_signed_elt int16_unsigned_elt int_elt int32_elt int64_elt nativeint_elt Big arrays can contain elements of the following kinds IEEE single precision 32 bits floating point numbers IEEE double precision 64 bits floating point numbers 8 bit integers signed or unsigned 16 bit integers signed or unsigned Caml integers signed 31 bits on 32 bit architectures 63 bits on 64 bit architectures 32 bit signed integers 64 bit signed integers platform native signed integers 32 bits on 32 bit architectures 64 bits on 64 bit architectures Each element kind is represented at the type level by one of the abstract types defined above type a b kind To each element kind is associated a Caml type which is the type of Caml values that can be stored in the big array or read back from it This type is not necessarily the same as the Chapter 28 The bigarray library 359 val val val val val val val val val val val type of the array elements proper for instance a big array whose elements are of kind float32_elt contains 32 bit single precision floats but reading or writing one of its elements from Caml uses the Caml type float which is 64 bit double precision floats The abstract typ
444. ve_top Similarly it makes the queue type abstract by not providing its actual representation as a concrete type module type PRIOQUEUE sig type priority int still concrete type a queue now abstract val empty a queue val insert a queue gt int gt a gt a queue val extract a queue gt int a a queue exception Queue_is_empty end module type PRIOQUEUE sig type priority int Chapter 4 The module system 61 and a queue val empty a queue val insert a queue gt int gt a gt a queue val extract a queue gt int a a queue exception Queue_is_empty end Restricting the PrioQueue structure by this signature results in another view of the PrioQueue structure where the remove_top function is not accessible and the actual representation of priority queues is hidden module AbstractPrioQueue PrioQueue PRIOQUEUE module AbstractPrioQueue PRIOQUEUE AbstractPrioQueue remove_top Unbound value AbstractPrioQueue remove_top AbstractPrioQueue insert AbstractPrioQueue empty 1 hello string AbstractPrioQueue queue lt abstr gt The restriction can also be performed during the definition of the structure as in module PrioQueue struct end PRIOQUEUE An alternate syntax is provided for the above module PrioQueue PRIQQUEUE struct end 4 3 Functors Functors are func
445. ver a colored point can be coerced to a point hiding its color method let colored_point_to_point cp cp colored_point gt point val colored_point_to_point colored_point gt point lt fun gt let p new point 3 and q new colored_point 4 blue val p point lt obj gt val q colored_point lt obj gt let 1 p colored_point_to_point q val 1 point list lt obj gt lt obj gt 48 An object of type t can be seen as an object of type t only if t is a subtype of t For instance a point cannot be seen as a colored point p point gt colored_point Type point lt get_offset int get_x int move int gt unit gt is not a subtype of type colored_point lt color string get_offset int get_x int move int gt unit gt Indeed backward coercions are unsafe and should be combined with a type case possibly raising a runtime error However there is no such operation available in the language Be aware that subtyping and inheritance are not related Inheritance is a syntactic relation between classes while subtyping is a semantic relation between types For instance the class of colored points could have been defined directly without inheriting from the class of points the type of colored points would remain unchanged and thus still be a subtype of points The domain of a coercion can usually be omitted For instance one can define let to_point c
446. was entered at top level module A sig contents of file a mli end struct contents of file a ml end The files defining the compilation units can be compiled separately using the ocaml c command the c option means compile only do not try to link this produces compiled interface files with extension cmi and compiled object code files with extension cmo When all units have been compiled their cmo files are linked together using the ocaml command For instance the following commands compile and link a program composed of two compilation units aux and main ocamlc c aux mli produces aux cmi ocamlc c aux ml produces aux cmo ocamlc c main mli produces main cmi ocamlc c main ml produces main cmo ocamlc o theprogram aux cmo main cmo The program behaves exactly as if the following phrases were entered at top level module Aux sig contents of aux mli end struct contents of aux ml end module Main sig contents of main mli end struct contents of main ml end In particular Main can refer to Aux the definitions and declarations contained in main ml and main mli can refer to definition in aux m1 using the Aux ident notation provided these definitions are exported in aux mli The order in which the cmo files are given to ocam1 during the linking phase determines the order in which the module definitions occur Hence in the example above Aux appears first an
447. ways using the break command Breakpoints are assigned numbers when set for further reference The most comfortable way to set breakpoints is through the Emacs interface see section 15 10 break Set a breakpoint at the current position in the program execution The current position must be on an event i e neither at the beginning nor at the end of the program break function Set a breakpoint at the beginning of function This works only when the functional value of the identifier function has been computed and assigned to the identifier Hence this command cannot be used at the very beginning of the program execution when all identifiers are still undefined use goto time to advance execution until the functional value is available break module line Set a breakpoint in module module or in the current module if module is not given at the first event of line line break module line column Set a breakpoint in module module or in the current module if module is not given at the event closest to line line column column break module character Set a breakpoint in module module at the event closest to character number character break address Set a breakpoint at the code address address delete breakpoint numbers Delete the specified breakpoints Without argument all breakpoints are deleted after asking for confirmation info breakpoints Print the list of all breakpoints 15 6 The call stack Each time
448. wo C functions The first function to be used in conjunction with the bytecode compiler ocamlc receives two arguments a pointer to an array of Caml values the values for the arguments and an integer which is the number of arguments provided The other function to be used in conjunction with the native code compiler ocamlopt takes its arguments directly For instance here are the two C functions for the 7 argument primitive Nat add_nat value add_nat_native value nati value ofsi value leni value nat2 value ofs2 value len2 value carry_in value add_nat_bytecode value argv int argn return add_nat_native argv 0 argv 1 argv 2 argv 3 argv 4 argv 5 argv 6 Chapter 17 Interfacing C with Objective Caml 195 The names of the two C functions must be given in the primitive declaration as follows external name type bytecode C function name_ native code C function name For instance in the case of add_nat the declaration is external add_nat nat gt int gt int gt nat gt int gt int gt int gt int add_nat_bytecode add_nat_native Implementing a user primitive is actually two separate tasks on the one hand decoding the arguments to extract C values from the given Caml values and encoding the return value as a Caml value on the other hand actually computing the result from the arguments Except for very simple primitives it is often preferable to have two distinct C functions to
449. x object self inherit restricted_point x method virtual move end class point_again int gt object val mutable x int method bump unit method get_x int method move int gt unit end The annotation virtual here is only used to mentioned a method without providing its definition An alternative definition is class point_again x object self lt move _ gt inherit restricted_point x end class point_again int gt object val mutable x int method bump unit method get_x int method move int gt unit end One could think that a private method should remain private in a subclass However since the method is visible in a subclass it is always possible pick it s code and define a method of the same name that run that code so yet another heavier solution would be class point_again x object self lt move _ gt inherit restricted_point x as super method move super move end class point_again int gt object val mutable x int method bump unit method get_x int method move int gt unit end Of course private methods can also be virtual Then the keywords must appear in this order method private virtual 42 3 6 Class interfaces Class interfaces are inferred from class definitions They may also be defined directly and used to restrict the type of a class As class declarations they also define a new type c
450. x file_descr gt buf string gt pos int gt len int gt int Input output with timeout val timed_read Unix file_descr gt buf string gt pos int gt len int gt timeout float gt int val timed_write Unix file_descr gt buf string gt pos int gt len int gt timeout float gt int Behave as read and write except that Unix_error ETIMEDOUT _ _ is raised if no data is available for reading or ready for writing after d seconds The delay d is given in the fifth argument in seconds Polling val select read Unix file_descr list gt write Unix file_descr list gt except Unix file_descr list gt timeout float gt Unix file_descr list Unix file_descr list Unix file_descr list Pipes and redirections val pipe unit gt Unix file_descr Unix file_descr val open_process_in string gt in_channel val open_process_out string gt out_channel val open_process string gt in_channel out_channel val open_process_full string gt env string array gt in_channel out_channel in_channel Time val sleep int gt unit 338 Sockets val val val val val val val val val val socket domain Unix socket_domain gt kind Unix socket_type gt proto int gt Unix file_descr socketpair domain Unix socket_domain gt kind Unix socket_type gt proto int gt Unix file_descr Unix file_descr accept Unix file_descr gt Unix file_descr Unix sockaddr
451. xpr type gt type see subsec tion 6 7 5 below Function application Function application is denoted by juxtaposition of possibly labeled expressions The expression expr argument argument evaluates the expression expr and those appearing in argument to argument The expression expr must evaluate to a functional value f which is then applied to the values of argument argument If a parameter is specified as optional label prefixed by in expr s type the corresponding argument will be automatically wrapped with the constructor Some except if the argument itself is also prefixed by in which case it is passed as is The order in which the expressions expr argument argument are evaluated is not spec ified The way in which arguments and parameters are matched depends on the compilation mode In the default or classic mode non optional arguments need not be explicitly labeled They will match the parameters in the order of definition In case arguments are labeled the label is checked against the parameter at compile time Optional arguments must be labeled They will be reordered according to their labels but a group of contiguous optional parameters in expr s type must be matched by a group of contiguous labeled arguments If there is one or more non labeled arguments after the optional ones optional parameters with no matching argument will be defaulted that is the value None will be passed for t
452. xpression zero one or several times postfix matches the previous expression one or several times postfix matches the previous expression once or not at all 325 326 val val val val character set ranges are denoted with as in a z an initial as in 70 9 complements the set T matches at beginning of line matches at end of line I infix alternative between two expressions C grouping and naming of the enclosed expression 1 the text matched by the first expression 2 for the second expression etc b matches word boundaries quotes special characters regexp_case_fold string gt regexp Same as regexp but the compiled expression will match text in a case insensitive way uppercase and lowercase letters will be considered equivalent quote string gt string Str quote s returns a regexp string that matches exactly s and nothing else regexp_string string gt regexp regexp_string_case_fold string gt regexp Str regexp_string s returns a regular expression that matches exactly s and nothing else Str regexp_string_case_fold is similar but the regexp matches in a case insensitive way String matching and searching val val val val string_match pat regexp gt string gt pos int gt bool string_match r s start tests whether the characters in s starting at position start match the regular expression r The first character of a string has position 0 as
453. y int Y coordinate of the mouse button bool true if a mouse button is pressed keypressed bool true if a key has been pressed key char the character for the key pressed To report events type event Button_down A mouse button is pressed Button_up A mouse button is released Key_pressed A key is pressed Mouse_motion The mouse is moved Poll Don t wait return immediately To specify events to wait for val wait_next_event event list gt status Wait until one of the events specified in the given event list occurs and return the status of the mouse and keyboard at that time If Poll is given in the event list return immediately with the current status If the mouse cursor is outside of the graphics window the mouse_x and mouse_y fields of the event are outside the range 0 size_x 1 0 size_y 1 Keypresses are queued and dequeued one by one when the Key_pressed event is specified Mouse and keyboard polling val mouse_pos unit gt int int Return the position of the mouse cursor relative to the graphics window If the mouse cursor is outside of the graphics window mouse_pos returns a point outside of the range 0 size_xQ 1 0 size_y 1 val button_down unit gt bool Return true if the mouse button is pressed false otherwise val read_key unit gt char Wait for a key to be pressed and return the corresponding character Keypresses ar
454. y Message Tk Focus Option Tkwait Frame Optionmenu Toplevel Grab Pack Winfo Grid Palette Wm Giving a detailed account of each of these module would be impractical here We will just present some of the basic functions in the module Tk Note that for most other modules information can be found in the Tcl man page of their name 27 1 Module Tk basic functions and types for LablTk Initialization and termination val openTk display string gt class string gt unit gt toplevel widget Initialize LablTk and open a toplevel window display is described according to the X11 conventions class is used for the X11 resource mechanism val mainLoop unit gt unit Start the main event loop val closeTk unit gt unit Quit the main loop and close all open windows val destroy a Widget widget gt unit Destroy an individual widget Application wide commands val update unit gt unit Synchronize display with internal state val appname_get unit gt string val appname_set string gt unit Get or set the application name Chapter 27 The LabITk library Tcl Tk GUI interface 353 Dimensions type units Pix int Cm float In float Mm float Pt float val pixels units gt int Converts various on screen units to pixels respective to the default display Available units are pixels centimeters inches millimeters and points Widget layout commands type anchor Center E N N
455. y a function on any argument creating a new function of the remaining parameters let f x y Xx y val f x int gt y int gt int lt fun gt f y 2 x 3 int 1 List fold_left 1 2 3 init 0 f 4 int 6 List fold_left init 0 f int gt a gt int gt a list gt int lt fun gt Optional parameters may also commute with non optional or unlabelled ones test z 1 y 2 x 3 int int int 3 2 1 As described in section 2 1 3 for out of order applications the type of the function must be known previous to the application otherwise an incompatible out of order type will be generated let h g g y 2 7x 3 val h y int gt x int gt a gt a lt fun gt h 355 This expression has type x int gt y int gt int but is here used with type y int gt x int gt a If in a function several arguments bear the same label or no label they will not commute among themselves and order matters But they can still commute with other arguments let hline x x1 x x2 y xl x2 y val hline x a gt x b gt y c gt a b c lt fun gt hline x 3 y 2 x 5 int int int 3 5 2 30 2 1 5 Suggestions for labeling Like for names choosing labels for functions is not an easy task A good labeling is a labeling which e makes programs more readable e is easy to remembe

The Objective Caml system release 3.00 - The Caml language

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