PERQ PERQ"PASCAL EXTENSIONS
Contents
1. handler Ex gin Handler for exception Ex ena procedure Procl begin raise Ex end procedure Proc2 handler Ex gin Handler for exception Ex end begin raise Ex Procl end begin raise Ex Proc2 Procl end produces the following output Global Handler for exception Ex Local Handler for exception Ex Local Handler for exception Ex Global Handler for exception Ex Handlers which already active are not eligible for reactivation In this case the search continues down the run time Stack until a non active handler is found A handler cannot therefore invoke itself by raising the same exception it was meant to handle If recursive procedure contains a handler each activation of the procedure has its own eligible handler 21 PERQ Pascal Extensions December 27 1983 If an exception is raised for which no handler is defined or eligible the system catches the exception and invokes the debugger A facility is provided to allow the user to catch such exceptions before the system does Handlers can be defined for the predefined exception ALL EXCEPTION ALL ES ER PStart PEnd integer where 1 ES is the system segment number of the exception 2 ER the routine number of the exception 3 PStart the stack offset of the first word of the exception S original parameters and 4 PEnd the stack offset of the word following the original param2. PERO Systems Corporation PERQ PASCAL EXTENSIONS March 1984 ts releases until further notice PERQ Pascal is ph paard compat ible extension of the standard programming language Pascal This document descr ibes only the extensions to Pascal Copyr ight C 1982 1983 P Systems Corpor amp tion 2500 Avenue D Box 2500 Pittsburgh PA 15230 412 355 0900 PERQ Pascal Extensions December 27 1983 This manual is for use with POS Release G 3 and subsequent releases until further notice PERQ Pascal is an upward compatible extension of the standard programming language Pascal This document describes only the extensions to PASCAL Copyright C 1982 1983 PERQ Systems Corporation 2600 Liberty Avenue P O Box 2600 Pittsburgh PA 15230 412 355 0900 This document is not to be reproduced in any form or transmitted in whole or in part without the prior written authorization of PERQ Systems Corporation The information in this document is subject to change without notice and should not be construed as commitment by PERQ Systems Corporation The company assumes no responsibility for any errors that may appear in this document PERQ Systems Corporation will make every effort to keep customers apprised of all documentation changes as quickly as possible The Reader s Comments card is distributed with this document to request users critical evaluation to assist us in prepar
3. Source Area Line Length Source Memory Pointer Note the values for the destination precede those for the source The arguments to RasterOp are defined below Function defines how the source and the destination are to be mbined to create the final picture stored at the destination The RasterOp functions are as follows Src represents the source and Dst the destination Function Name Action 0 RRpl Dst gets Src 1 RNot Dst gets NOT Src 2 RAnd Dst gets Dst AND Src 3 RAndNot Dst gets Dst AND NOT Src 4 ROr Dst gets Dst OR Src ROrNot Dst gets Dst OR NOT Src 6 RXor Dst gets Dst XOR Src 7 RXNor Dst gets Dst XNOR Src The symbolic names are exported by the file Raster Pas Width specifies the size in the horizontal x direction of the source and destination rectangles given in bits Height specifies the size in the vertical y direction of the source and destination rectangles given in scan lines Destination X Position is the bit offset of the left side of the destination rectangle The value is offset from Destination Memory Pointer see below 2 31 PERQ Pascal Extensions December 27 1983 Destination Y Position is the scan line offset of the top of the destination rectangle The value is offset from Destination Memory Pointer see below Destination Area Line Length is the number of words which comprise a line in the destination region hence defining the region s width T
4. filename where filename is the name of the file to be written The extension ERR will be appended to filename if it is not already present If filename is not specified the compiler uses the source file name If the PAS extension is present it is replaced with the ERR extension else if the PAS extension is not present the ERR extension is appended The error file exists after a compilation if and only if you specify the ERRORFILE switch and an error is encountered If the file filename ERR already exists from a previous compilation it will be rewritten or deleted in the case of no compiliation errors This switch allows compilations to be left unattended 19 2 13 Help Switch The Help switch provides general information and overrides all other switches The format is HELP dd PERQ Pascal Extensions December 27 1983 20 0 Quirks and Other Oddities The following are descriptions of known quirks and problems with the PERQ Pascal compiler Future releases may correct these problems 1 FOR loops with an upper bound of greater than 32 766 never terminate 2 The last line of any PROGRAM or MODULE must end with a carriage return or an Unexpected End of Input error occurs 3 Although unique abbreviations are accepted for switches the following abbreviations cause compilation errors Switch Bad Abbreviation ELSEC ELSE ENDC SEND IFC IF INCLUDE IN 4 Procedu
5. double precision integer 18 15 Shrink The Shrink intrinsic converts a double precision integer to a single precision integer If the double precision integer is outside the range of 32768 to 32767 a runtime error occurs PERQ Pascal Extensions December 27 1983 19 Command Line and Compiler Switches 19 1 Command Line The PERQ Pascal compiler is invoked by typing a compile command hee to the PERQ Operating The syntax for the compile command ine is COMPILE InputFile lt OutputFile gt lt Switch gt lt InputFile gt is the name of the source file to be compiled The compiler searches for lt InputFile gt If it does not find lt InputFile gt it appends the extension PAS and searches again If lt InputFile gt is still not found the user will be prompted for an entire command line If lt InputFile gt is not specified the compiler uses for lt InputFile gt the last file name remembered by the system OutputFile is the name of the file to contain the output of the compiler The extension SEG will be appended to lt OutputFile gt if it is not already present Note that if lt OutputFile gt is not specified the compiler uses the file name from InputFile Then if the PAS extension is present it is replaced with the SEG extension else if the PAS extension is not present the SEG extension is appended If lt OutputFile gt already exists it will be rewritten lt Switch g
6. descriptor is left on the expression stack of the PERQ and any further operations must be performed by the user This procedure takes one ameter the name of the function or procedure for which the variable routine descriptor is to be loaded The use of this intrinsic assumes that the programmer is familiar with QCode primarily a hacker s intrinsic 18 6 InLineByte InLineByte permits the user to place explicit bytes directly into the code stream generated by the compiler This intrinsic is particulary useful for insertion of actual QCodes into a program InLineByte requires one parameter the byte to be inserted The type of this parameter must be either integer or subrange of integer 18 7 InLineWord InLineWord permits the user to place explicit words directly into the code stream generated by the compiler This intrinsic is rticulary useful for insertion of direct QCodes into a program nLineWord requires one parameter the word to be inserted This word PERQ Pascal Extensions December 27 1983 will be inserted immediately as the next two bytes of the code stream no word alignment is performed The type of this parameter must be either integer or subrange of integer 18 8 InLineAWord InLineAWord permits the user to place explicit words directly into the code stream generated by the compiler This intrinsic is particulary useful for insertion of direct QCodes into a progran InLineAWord requires one parameter t
7. from a module it is local to that module and cannot be used by other modules Likewise all identifiers referenced in a module must be either local to the module or imported from another module Modules do not contain a main statement body A program is a special instance of a module and conforms to the definition of a program given by the PASCAL User Manual and Report JW74 Only a program may contain a main body and every executable group of modules must contain exactly one instance of a program Exporting allows a module to make constants types variables procedures and functions available to other modules Importing allows a module to make use of the EXPORTS of other modules Global constants types variables procedures and functions can be declared by a module to be private available only to code within the module or exportable available within the module as well as from any other module which imports them Modules which contain only type and constant declarations cause no run time overhead making them ideal for common declarations It should also be noted that such modules may not be compiled as errors will be produced however they may be successfully imported 13 1 IMPORTS Declaration The IMPORTS Declaration specifies the modules which are to be imported into a module The declaration includes the name of the module to be imported and the file name of the source file for that module When compiling an import declar
8. is to specify the code to be executed when the exception condition occurs This is done by defining a handler with the same name and parameter types as the declared exception for example HANDLER DivisionByZero Top integer lt block gt See Declaration Relaxation in this document for a definition of lt block gt Essentially a handler looks like a procedure with the word HANDLER substituted for the word PROCEDURE Handlers may appear in the same places procedures are allowed with one difference Handlers cannot be global to a module they may however be global to the main program The number and type of parameters of a handler must match those of the corresponding exception declaration but the names of the parameters may be different Multiple handlers can exist for the same exception as long as there is only one per name scope The exception must be declared before its handler s Raising an exception is analogous to a procedure call The word eee before the name and parameters of the exception for example RAISE DivisionByZero N causes the appropriate handler to execute The appropriate handler is determined by the current subprogram calling sequence The run time stack is searched until a subprogram containing a handler of the same is found The search starts from the subprogram which issues the 20 PERQ Pascal Extensions December 27 1983 For example program ExampleException exception Ex
9. it may only be used in comment form within a program PERQ Pascal Extensions December 27 1983 19 2 2 List Switch The List Switch controls whether or not the compiler generates a program listing of the source text The default is to not generate a list file The format for the List switch is LIST filename or LIST filename where filename is the name of the file to be written The extension LST will be appended to filename if it is not already present If filename is not specified the compiler uses the source file name If the PAS extension is present it is replaced with the LST extension else if the PAS extension is not present the LST extension is appended Like the file inclusion mechanism in the comment form of the switch the filename is taken as all characters between the LISI and the jy ignoring leading spaces and tabs hence no other options may be included in this comment With each source line the compiler prints the line number segment number and procedure number 19 2 3 Range Checking This switch is used to enable or disable the generation of additional code to perform checking on array subscripts and assignments to subrange types Default value Range checking enabled RANGE or RANGE enables range checking RANGE or NORANGE disables range checking RANGE resumes the state of range checking which was in force before the previous SRANGE or RANGE sw
10. range 32768 to 32767 is considered single precision an INTEGER Constants exceeding this range are considered double precision LONG The maximums for double precision constants are 2147483648 and 42147483647 When using octal constants a constant with the 16th bit set is interpreted as a negative integer not as a positive long integer 4 3 Constant Expressions PERQ Pascal extends the definition of a constant to include expressions which may be evaluated at compile time Constant expressions support the use of the arithmetic operators x DIV MOD and the logical operators AND OR and NOT the type coercion functions CHR ORD and RECAST the WORDSIZE intrinsic and previously defined constants See WordSize in this manual and RECAST under Type Compatibility also in this manual All logical operations are performed as full 16 bit operations PERQ Pascal Extensions December 27 1983 The new syntax for constants is constant string constant constant expression constant expression lt csimple constant expression constant expression relational operator csimple constant expression relational operator o lt lt gt gt simple constant expression lt cterm lt sign gt lt cterm simple constant expression gt lt adding operator gt lt cterm adding operator 1 OR sign lt cterm gt lt cfactor gt lt cter
11. EXPORTS Declaration section If a program is to contain no EXPORTS Declaration section the inclusion of PRIVATE following the program heading is optional PRIVATE is assumed Note A module with no EXPORTS would be useless since its contents could never be referenced it only makes sense for a program not to have any EXPORTS The new syntax for a unit of compilation is compilation unit module program program program heading gt lt module body gt lt statement part module module heading gt lt module body program heading PROGRAM identifier file identifier file identifier gt lt module MODULE lt identifier gt lt module body EXPORTS lt declaration part gt PRIVATE lt declaration part PRIVATE declaration part declaration part 19 PERQ Pascal Extensions December 27 1983 14 0 Exceptions PERQ Pascal provides an exception handling facility Exceptions are typically used for error conditions There are three steps to using an exception 1 The exception must be declared 2 A handler for the exception must be defined 3 The exception must be raised An exception is declared by the word EXCEPTION followed by its name and optional list of parameters For example EXCEPTION DivisionByZero Numerator integer Exceptions can be declared anywhere in the declaration portion of a program or module The second step
12. If the base type of a set is a subrange of integer that subrange must be within the range 0 4079 inclusively If the base type of a set is a subrange of an enumerated type the cardinal number of the largest element of the set must not exceed 079 s 10 PERQ Pascal Extensions December 27 1983 9 Record Comparisons PERQ Pascal supports arison of records with one restriction No portion of the records can be packed For example program P input output var R1 R2 record RealPart integer Imagine integer end begin RI RealPart 1 Rl Imagine 2 R2 RealPart 1 R2 Imagine 2 M R2 then writeln Records equal e produces as output Records equal 21 PERQ Pascal Extensions December 27 1983 10 Strings PERQ Pascal includes a string facility which provides variable length strings with a maximum size limit imposed upon each string The default maximum length of a SIRING variable is 80 characters This may be overridden in the declaration of a STRING variable by appending the desired maximum length must be a compile time constant within square brackets after the reserved type identifier STRING There is absolute maximum of 255 characters for all strings The following are example declarations of SIRING variables Line SIRING defaults to a maximum length of 80 characters ShortStr STRINGI 12 maximum length of ShortStr is 12 characters Assignm
13. LE 15 File Inclusion 37 Files 3 FLOAT 34 Floating Point Numbers 3 Function Result Type 17 Functions 17 Generic Files 15 Generic Pointers 14 HANDLER 20 Help switch 43 Identifiers 2 IFC 41 INCLUDE 37 Inclusive Or 25 INLINEAWORD 34 INLINEBYTE 33 INLINEWORD 2 Input Output Intrinsics 24 PERQ Pascal Extensions December 27 1983 INTEGER Logical Operati 25 ca rations LAND 25 LENGTH 13 LIST 38 LNOT 25 LOADADR 34 LOADEXPR 34 LONG 3 LOR 25 LXOR 25 MAKEPTR 33 MAKEVRD 33 MESSAGE 41 Miscellaneous Intrinsics 30 Mixed Mode Expressions 4 Modules 18 NEW 23 NOT 25 Numbers 3 OR OTHERWISE 8 Parameter Lists 17 Parameters 017 POINTER 14 PRIVATE _ 19 Procedure Function Name 40 Procedures 17 QUIET 39 Quirks 44 RAISE 20 RANGE 38 Range Checking 38 RASTEROP 30 READ 27 READLN 27 REAL 3 RECAST 7 Record Comparisons 11 References 46 T 27 REWRITE 27 ROTATE 26 Sets 10 SHIFT 25 SHRINK 35 Single and Double Precision Constants 5 Single Precision Logical Operations 25 STARTIO 30 SIOREXPR 34 48 PERQ Pascal Extensions December 27 1983 STRETCH STRING Strings Switches Symbols Switch Type Coercion Type Coercion Intrinsics Type Compatibility VERSION Whole Number Constants Whole Numbers WORDSIZE WRITE WRITELN SRVRunSiuwuBSRSpe 49
14. acteristic If the desired allocation from any call to NEW cannot be performed a NIL pointer is usually returned However if memory is exhausted the FULLMEMORY exception may be raised If the call to NEW fails and raises FULLMEMORY the user program will abort unless it 23 PERQ Pascal Extensions December 27 1983 includes a handler for FULLMEMORY 15 2 DISPOSE DISPOSE is identical to the definition given in PASCAL User Manual and Report JW74 Note that the segment and alignment are never given to DISPOSE only the pointer and tag field values 24 PERQ Pascal Extensions December 27 1983 16 Single Precision Logical Operations The PERQ Pascal compiler supports a variety of single precision INTEGER logical operations The operations supported include and inclusive or not exclusive or shift and rotate The syntax for their use resembles that of a function call however the code is generated inline to the procedure hence there is no procedure call overhead associated with their use The syntax for the logical functions are described in the following sections 16 1 And Function LAND Vali Val2 integer integer LAND returns the bitwise AND of Vall and Val2 16 2 Inclusive Or _ Function LOR Val1 Val2 integer integer LOR returns the bitwise INCLUSIVE OR of Vall and Val2 16 3 Not Function LNOT Val integer integer LNOT returns the bitwise complement of Val 16 4 Exclusive Or Func
15. ameter the item whose size is desired and returns an integer Note WordSize generates compile time constants and hence may be used in constant expressions PERQ Pascal Extensions December 27 1983 18 4 MakePtr The MakePtr intrinsic permits the user to create a pointer to data type given a system segment number and offset Its use is intended for those who are familiar with the system and are sure of what they are doing The function takes three parameters The first two are the system segment number and offset within that segment to be used in creating the pointer respectively given as integers The last parameter is the type of the pointer to be created MakePtr returns a pointer of the type named by the third parameter Note The next seven intrinsics MakeVRD InLineByte InLineWord InLineAWord LoadExpr LoadAdr and StorExpr require that the user have knowledge of how the compiler generates code which will not be discussed here These intrinsics are intended for system hacking and are made available for those who know what they are doing The programmer who wishes to experiment with these may find the QCode disassembler QDIS is very useful to determine if the desired results were produced 18 5 MakeVRD MakeVRD is used to load a variable routine descriptor for a procedure or function See Routine Calls and Returns for a description of LVRD and CALLV in the QCode Reference Manual The variable routine
16. ation the source file containing the module to be imported must be available to the compiler Note If the module is composed of several INCLUDE files only those files from the file containing the program or module heading through the file which contains the word PRIVATE must be available See Compiler Switches in this manual The syntax for the IMPORTS declaration is import declaration part IMPORTS module name FROM file name 18 PERQ Pascal Extensions December 27 1983 13 2 EXPORTS Declaration Section If a program or module is to contain any exports the EXPORTS Declaration section must immediately follow the program or module heading The EXPORTS Declaration section is comprised of the word EXPORTS followed by the declarations of those items which are to be exported These definitions are given as previously specified with one exception procedure and function ies are not given in the exports section Only forward references are given See Declaration Relaxation in this manual See Chapter 11 2 in the PASCAL User Manual and Report JW74 The inclusion of FORWARD in the EXPORTS reference is omitted The EXPORTS Declaration section is terminated by the occurrence of the word PRIVATE This signifies the beginning of the declarations which are local to the module The PRIVATE Declaration section must contain the declarations and bodies for all procedures and functions defined in the
17. ation returns to whatever state was present prior to the most recent IFC The remaining switch is the ELSEC switch and it functions much in the same way as the else clause in an IF statement If the boolean expression of the IFC switch is true then the text is ignored otherwise it is included If a ELSEC switch is used no ENDC preceeds the ELSEC the ELSEC signals the end of the IFC PEE A ENDC is then used to terminate the ELSEC clause Conditional compilations may be nested The following are two examples of the conditional compilation mechanism Const Cond TRE Snc Test STFC CondSw THEN Writeln CondSw is true ENDC end Test TYPE Base record i j k integer end IFC WORDSIZE Base 3 THEN a array 0 2 of integer ELSEC Cover 0 101 of integer ENDC 19 2 12 Errorfile Switch When the compiler detects an error in a program it displays error information file error number and the last two lines where the error occurred on the screen and then requests whether or not to continue The ERRORFILE switch overrides this action When you 42 PERQ Pascal Extensions December 27 1983 specify the switch and the compi ler detects an error the error information is written to a file and there is no query of the user However the compiler does display the total ner of errors encountered on the screen The format for this switch is ERRORFILE
18. char end the actual characters go here 10 1 LENGTH Function The predefined integer function LENGTH is provided to return the dynamic length of a string For example program LenExample input output var Line string Len integer begin Line his is a string with 35 characters end assigns the value 35 into Len 232 PERQ Pascal Extensions December 27 1983 11 Generic Types Generic types are general forms of more specific types PERQ Pascal provides two predefined generic types 1 Pointers 2 Files 11 1 Generic Pointers Generic pointers provide a tool for generalized pointer handling Variables of type POINTER can be used in the same manner as any other pointer variable with the following exceptions 1 Since there is no notion of type associated with the reference variable of a generic pointer generic pointers cannot be dereferenced 2 Generic pointers cannot be used as an argument to NEW or DISPOSE 3 Any pointer type can be passed to a generic pointer x To make use of a generic pointer RECAST should used to convert the pointer to some usable pointer type 14 PERQ Pascal Extensions December 27 1983 The following is a sample program utilizing generic pointers program P input output type Ptrint integer PAOfChar packed array 1 2 of char PtrPAOfChar PAOfChar var PtrInt C PtrPAOfChar procedure Procl GenPtr pointe
19. d Line and Compiler Switches 19 Command Line 19 2 Compiler Switches 19 2 1 File Inclusion 19 2 2 List Switch 19 2 3 Range Checking 19 2 4 Quiet Switch 19 2 5 Symbols Svitch 19 2 6 Automatic RESET REWRITE 19 2 7 Procedure Function Names 19 2 8 Version Switch 19 2 9 Comment Switch 19 2 10 Message Switch iv December 27 1983 PERQ Pascal Extensions December 27 1983 19 2 11 Conditional Compilation 19 2 12 Errorfile Switch 19 2 13 Help Switch 20 Quirks and Other Oddities 2l Refererices Index sal Extensi 27 1983 PERQ Pascal Extensions December vi PERQ Pascal Extensions December 27 1983 1 Introduction PERQ Pascal is an upward compatible extension of the programming language Pascal defined in PASCAL User Manual and Report JW74 This document describes only the extensions to Pascal Refer to PASCAL User Manual and Report for a fundamental definition of Pascal This document uses the BNF notation used in PASCAL User Manual and Report The existing BNF is not repeated but is used in the syntax definition of the extensions The semantics are defined informally These extensions are designed to support the construction of large systems programs A major attempt has been made to keep the goals of Pascal intact In particular attention is directed at simplicity efficient run time implementation efficient compilation language security upward compatibility and compile time checking These ext
20. e Longs as assignments arithmetic expressions 11 The RECAST intrinsic does not work with two word scalers for example LONG and arrays 45 PERQ Pascal Extensions mM December 27 1983 20 References BSI79 BSI ISO Pascal Standard Computer April 1979 FPS0 An Implementation Guide to a Proposed Standard for Floating Point Computer January 1980 JW74 K Jensen and N Wirth PASCAL User Manual and Report Springer Verlag New York 1974 P J Hennessy and F Baskett Pascal A Pascal Based Systems Programming Language Stanford University Computer Science Department TRN 174 August 1979 UCSD79 K Bowles Proceedings of UCSD Workshop on System Programming Extensions to the Pascal Language Institute for Information Systems University of California San Diego California 1979 PERQ Pascal Extensions December 27 1983 INDEX Entries entirely in upper case are reserved words or predeclared identifiers ALL root Co ibili Signment Compat t Automatic RESPT REWRITE CASE Statement CLOSE Command Line Comment Switch _ Compiler Switches Conditional Compilation Constant Expressions Constants Control Structures Declaration Relaxation Declarations DISPOSE Dynamic Space Allocation and Deallocation ELSEC ENDC Error notification file Errorfile Switch oOhSSSS EBSwwoan K KVos S EXCEPTION Exceptions Exclusive _ EXIT Statement EXPORTS Declaration 19 FI
21. e end of the comment or the end of the line If the comment exceeds a single line the remainder of the comment is ignored 19 2 10 Message Switch The Message Switch causes the text of the switch to be printed on the user s screen when the switch is parsed by the compiler It has no effect on the compilation process The format for this switch is fMESSAGE string to print string on the console during compilation The message is terminated by the end of the comment or the end of the line If the comment exceeds a single line the remainder of the comment is ignored Note There is no command line form for this switch it may only be used in its comment form 19 2 11 Conditional Compilation The PERQ Pascal conditional compilation facility is implemented through the standard switch facility There are three switches which are used for conditional compilations The first is the IFC switch which has the following form IFC boolean expression THEN E I PERQ Pascal Extensions December 27 1983 This switch indicates the beginning of region of conditional compilation If the boolean expression evaluated at compile time is true the text to follow is included in the compilation If the boolean expression evaluates to false then the text which follows is not included The region of conditional is terminated by the ENDC switch SENDC Upon encountering the ENDC switch the state of compil
22. e to be activated 18 2 RasterOp pi ains is a special QCode which is used to manipulate blocks of memory of arbitrary sizes It is especially useful for creating and modifying displays on the screen RasterOp modifies a rectangular area called the destination of arbitrary size to the bit picture drawn into this rectangle is computed as a function of the previous contents of the destination and the contents of another rectangle of the same size called the source The functions performed to combine the two pictures are described below To allow RasterOp to work on memory other than that used for the screen bitmap RasterOp has parameters that specify the areas of memory to be used for the source and destination a pointer to the start of the memory block and the width of the block in words Within these regions the positions of the source and destination rectangles are given as offsets from the pointer Thus position 0 0 would be at the upper left corner of the region and for the screen 767 1023 would be the lower right The operating system module Screen exports useful parameters PERQ Pascal Extensions December 27 1983 The compiler supports a RASTEROP intrinsic which may be used to invoke the RasterOp QCode The form of this call is RASTEROP Function Width Height Destination X Position Destination Y Position Destination Area Line Length Destination Memory Pointer Source X Position Source Y Position
23. ensions to the language are derived from the BSI ISO Pascal Standard BSI79 the UCSD Workshop on Systems Programming to the Pascal Language UCSD79 and most notably Pascalx Xl PERQ Pascal Extensions December 27 1983 2 Declarations You must declare all data items in a Pascal program To declare a data item specify the identifier and then what it represents 2 1 Identifiers o 7 You can include the underscore character character in identifiers as a significant 2 2 Declaration Relaxation The order of declaration for labels constants types variables procedures and functions has been relaxed These declaration sections may occur in any order and any number of times It is required that an depo e be declared before it is used Two exist to this rule 1 Pointer types may be forward referenced as long as the declaration occurs within the same type definition part and 2 Procedures and functions may be predeclared with a forward declaration The new syntax for the declaration section is lt block gt lt declaration part gt lt statement part gt declaration part declaration declaration declaration part kapa empty rt declaration part 218 declaration part constant definition part type definition part variable declaration part procedure and function declaration part Note See IMPORTS Declaration in this docum
24. ent PERQ Pascal Extensions December 27 1983 2 3 Files PERQ Pascal permits the use of files as the component type of arrays pointers and record fields 3 Numbers 3 1 Whole Numbers Single precision whole numbers are of the predefined type INTEGER They occupy 16 bits 15 bits and a sign bit and range in value from 32768 to 32767 Whole numbers of the predefined t LONG are double precision They occupy 32 bits 31 bits and a sign bit and range in value from 2147483648 to 42147483647 Arithmetic operations and comparisons are defined for both single and double precision whole numbers You can only use Longs as assignments in arithmetic expressions See the section Extended Constants for a discussion of single and double precision constants 3 2 Floating Point Numbers PERQ Pascal floating point numbers type REAL occupy 32 bits and conform to the IEEE floating point format See FP80 Positive values range from approximately 1 1754945e 38 to 3 402823e 38 and negative values range from approximately 1 1754945e 38 to 3 402823e 38 Arithmetic operations and comparisons are defined for floating point numbers 3 3 Type Coercion Intrinsics The STRETCH intrinsic can be used to explicitly convert a single precision whole number into a double precision whole number The SHRINK intrinsic converts double precision into single precision provided that the value of the double precision number is within the legal range of s
25. ents to string variables may be performed using the assignment statement or by means of a READ statement Assignment of one STRING variable to another may be performed as long as the dynamic length of the source is within the range of the maximum length of the destination the maximum length of the two strings need not be the same The individual characters within a STRING may be selectively read and written The characters are indexed starting from 1 through the dynamic length of the string For example program StrExample input output var Line string 25 Ch char begin Line this is an example Line 11 2 T Line now begins with upper case Ch now contains a space end A STRING variable may not be indexed beyond its dynamic length The fol lowing instructions if placed in the above program would produce an invalid index run time error Line 12345 Ch Linel 6 STRING variables and constants may be compared regardless of their dynamic and maximum lengths The resulting comparison is lexicographical according to the ASCII character set The full 8 bits are compared hence the ASCII Bit bit 7 is significant for lexical comparisons 12 PERQ Pascal Extensions December 27 1983 A SIRING variable with maximum length N can be conceived as having the following internal form packed record DynLength 0 255 the dynamic length Chrs d array 1 N of
26. eters Any raised exception that does not have an eligible handler in the same or suceeding level of the calling sequence in which an ALL handler is defined is caught by that ALL handler The four integer parameter values are calculated by the system and supplied to the ALL handler Extreme caution should be used when defining an ALL handler as the handler also catches system exceptions All cannot be raised explicitly The ability to chine ALL handlers is intended for systems hackers only The operating system providet several default handlers Information on these handlers can be found in the Program System and Module Except descriptions in the Operating System Manual Since exceptions are generally used for serious errors careful consideration should be given as to whether or not execution should be resumed after an exception is raised When a handler terminates execution resumes at the place following the RAISE statement The handler can of course explicitly dictate otherwise The EXIT and GOTO statements may prove useful here See Control Structures in this manual PERQ Pascal Extensions December 27 1983 15 0 Dynamic Space Allocation and Deallocation The PERQ Pascal Compiler supports the dynamic allocation procedures NEW and DISPOSE defined on page 105 of PASCAL User Manual and Report JW74 along with several upward compatible extensions which permit full utilization of the PERQ memory arch
27. forced termination of procedures or functions The statement can exit from the current procedure or function or from any of its parents EXIT takes the procedure or function name to exit from as a parameter Note that the use of an EXIT statement to return from a function can result in the function returning undefined values if no assignment to the function identifier is made prior to executing the EXIT statement Below is an example use of the EXIT statement program ExitExample input output var Str string rocedure P gin readin Str writeln Str if Str This is the first line then E exit ExitExample ena 59812 while Str Last Line do begin readin Str writeln Str end end If the above program is supplied with the following input This is the first line This is another line Last Line the following output would result This is the first line If the procedure or function to be exited has been called recursively then the most recent invocation of that procedure exits WARNING The parameter to EXIT can be any procedure or function name If the specified routine is not on the call stack the PERQ crashes 29 PERO Pascal Extensions December 27 1983 8 Sets PERQ Pascal supports all of the constructs defined for sets Chapter 8 of PASCAL User Manual end Report JW74 Space is allocated for sets in a bit wise fashion at most 255 words for a maximum set size of 4 080 elements
28. he appropriate value to use when operating on the screen is 48 The specified value must be a multiple of four 4 and within the range 4 through 48 Destination Memory Pointer is the 32 bit virtual address of the top left corner of the destination region it may be a pointer variable of any type This pointer MUST be quad word aligned however See New in this document for details on buffer alignment Source X Position is the bit offset of the left side of the source rectangle The value is offset from Source Memory Pointer see below Source Y Position is the scan line offset of the top of the source rectangle The value is offset from Source Memory Pointer see below Source Area Line Length is the number of words which comprise a line in the source region hence defining the region s width The appropriate value to use when operating on the screen is 48 The specified value must be a sau aa of four 4 and within the range 4 through 48 Source Memory Pointer is the 32 bit virtual address of the top left corner of the source region it may be a pointer variable of any type This pointer MUST be quad word aligned however See New in this document for details on buffer alignment 18 3 WordSize The WordSize intrinsic returns the number of words of storage required for any item which has a size associated with it This includes constants types variables and functions The intrinsic takes single par
29. he word to be inserted This word is placed on the next word boundary of the code stream The type of this parameter must be either integer or subrange of integer 18 9 LoadExpr The LoadExpr intrinsic takes an arbitrary expression as its parameter and loads the value of the expression The result of the load is wherever the particular expression type would normally be loaded expression stack for scalars memory stack for sets etc 18 10 LoadAdr The LoadAdr intrinsic loads the address of an arbitrary data item onto the expression stack The parameter to LoadAdr the item whose address is desired may include array indexing pointer dereferencing and field selections The address which is left on the expression stack will be a virtual address if the parameter includes either the use of a VAR parameter or a pointer dereference otherwise a 20 bit stack offset will be loaded 18 11 StorExpr StorExpr stores the single word on top of the expression stack in the variable given as a parameter The destination for the store operation must not require any address computation the destination must be a local intermediate or global variable it must not be a VAR parameter if it is a record a field specification may be given 18 12 Float The Float intrinsic converts an integer into a floating point number PERQ Pascal Extensions December 27 1983 18 13 Stretch The Stretch intrinsic converts a single precision integer to a
30. ing future documentation PERQ and PERQ2 are trademarks of PERQ Systems Corporation PERQ Pascal Extensions December 27 1983 QN OON C N an 9 NN AM aaa wwwwww NNNN J TABLE OF CONTENTS Introduction Declarations Identifiers Declaration Relaxation Files Numbers Whole Numbers Floating Point Numbers Type Coercion Intrinsics Assignment Compatibility Mixed Mode Expressions Extended Constants Constant Expressions Unsigned Octal Whole Numbers Type Compatibility Type Coercion RECAST Extended Case Statement Control Structures EXIT Statement Sets Record Comparisons Strings Length Function Generic Types Generic Pointers Generic Files Procedure Function Parameter Types Parameter Lists Function Result Type Procedures and Functions as Parameters Modules IMPORTS EXPORIS iii PERQ Pascal Extensions Except ions 14 T nane Space Allocation and Deallocation 15 New 15 2 Dispose 16 Single Precision Logical Operations 16 1 And 16 2 Inclusive Or 16 3 Not 16 4 Exclusive Or 16 5 Shift 16 6 Rotate 17 Input Output Intrinsics 17 1 REWRITE 17 2 RESET 17 3 READ READLN 17 4 WRITE WRITELN 17 5 CLOSE 18 Miscellaneous Intrinsics 18 1 StartIO 18 2 Raster Op 18 3 WordSize 18 4 MakePtr 18 5 MakeVRD 18 6 InLineByte 18 7 InLineWord 18 8 InLineAWord 18 9 LoadExpr 18 10 LoadAdr 18 11 StorExpr 18 12 Float 18 13 Stretch 18 14 Shrink 19 Comman
31. ingle precision If it is not a runtime error occurs The FLOAT intrinsic converts a single precision whole number into a floating point number TRUNC and ROUND convert a floating point number into a single precision whole number provided that the value of the floating point number is within the legal range of single precision If not a runtime error occurs The module CONVERT described in the PERQ Operating System Manual provides three functions to convert a floating point number into a double precision whole number or vice versa PERQ Pascal Extensions December 27 1983 For example real long integer e 29 FLOAT I TRUNC R pest U waq OY 3 4 Assignment Compatibility Single precision whole numbers are assignment compatible with double precision whole numbers and floating point numbers That is expressions of type INTEGER can be assigned to variables of type LONG or REAL and INTEGER expressions can be passed by value only to LONG or REAL formal parameters Double precision whole numbers and floating point numbers are not assignment compatible with single precision whole numbers The type coercion intrinsics SHRINK FLOAT and TRUNC can be used for this purpose The module CONVERT described in the PERQ Operating System Manual allows assignments between double precision whole numbers and floating point numbers 3 5 Mixed Mode Expressions Mixed mode expressions between single and double prec
32. ion in the command line preceded by the slash character The actual switches provided by the PERQ Pascal compiler although similar in syntax bear little resemblance to the switches described in PASCAL User Manual and Report JW74 The following sections describe the various switches currently supported by the PERQ Pascal Compiler 19 2 1 File Inclusion The PERQ Pascal compiler may be directed to include the contents of secondary source files in the compilation The effect of using the file inclusion mechanism is identical to having the text of the secondary file s present in the primary source file the primary source file is that file which the compiler was told to compile To include a secondary file the following syntax is used INCLUDE FILENAME The characters between the INCLUDE and the are taken as the name of the file to be included leading spaces and tabs are ignored The comment must terminate at the end of the filename hence no other options can follow the filename If the file FILENAME does not exist PAS will be concatenated onto the end of FILENAME and a second attempt will be made to find the file The file inclusion mechanism may be used anywhere in a program or module and the results will be as if the entire contents of the include file were contained in the primary source file the file containing the include directive Note There is no form of this switch for the command line
33. ision whole numbers or between single precision whole numbers and floating point numbers allowed Mixed mode expressions containing double precision whole numbers and floating point numbers are not allowed IMPORTANT NOTE mixed mode expression is evaluated from left to right taking normal operator precedence and parentheses into account in single precision mode until the first LONG or REAL is encountered Starting at that point all single precision operands are converted to double precision or floating point before used in evaluation Single precision overflow or underflow can occur while single precision mode The STRETCH or FLOAT intrinsics may be used to avoid this problem PERQ Pascal Extensions December 27 1983 4 Extended Constants 4 1 Whole Number Constants Unsigned octal whole number INTEGER or LONG constants are supported as are decimal constants Octal constants are indicated by a amp preceding the number The syntax for an unsigned integer is unsigned integer unsigned decimal integer unsigned octal integer unsigned decimal integer lt digit gt lt digit gt unsigned octal integer lt ogit gt lt ogit gt lt digit gt 20111213141516171819 ogit 2011121314151617 NOTE Unsigned constants do not imply unsigned arithmetic For example 177777 has the value 1 not 65535 4 2 Single and Double Precision Constants A constant in the
34. itch If RANGE is not followed by a or then is assumed Note that pex compiled with range checking disabled run slightly faster but invalid indices go undetected Therefore until a is fully debugged it is advisable to keep range checking enabled PERQ Pascal Extensions December 27 1983 19 2 4 Quiet Switch This switch is used to enable or disable the Compiler from displaying the name of each procedure and function as it is compiled Default value Display of procedure and function names enabled S QUIET or VERBOSE enables display of procedure and function names SQUIET or QUIET disables display of procedure and function names SQUIET resumes the state of the quiet switch which was in force before the previous QUIET or QUIET switch If QUIET is not followed by or then is assumed 19 2 5 Symbols Switch This switch is used to set the number of symbol table swap blocks used by the Compiler As the number of symbol table swap blocks increases compiler execution time becomes shorter however physical memory requirements increase and the Compiler may abort due to insufficient memory The format for this switch is SYMBOLS lt of Symbol Table Blocks Note There is no comment form of this switch it may only be used on a command line The default number of symbol table blocks and the maximum number of symbol table blocks are both dependent on
35. itecture There are two features of PERQ s memory architecture which require extensions to the standard allocation procedures First there are situations which require particular alignment of memory buffers such as IO operations Second PERQ supports multiple data segments from which dynamic allocation may be performed This facilitates grouping data together which are to be accessed together which may improve PERQ s performance due to improved swapping Data segments are multiples of 256 words in size and are always aligned on 256 word boundaries For further information of the memory architecture and available functions see the documentation on the memory manager 15 1 NEW If the standard form of the NEW procedure call is used NEW Ptr Tagi TagN memory for Ptr is allocated with arbitrary alignment from the default data segment The extended form of the NEW procedure call is NEW Segnent Alignment Ptr Tagl TagN Segment is the segment number from which the allocation is to be performed This number is returned to the user when creating a new data segment The value 0 is used to indicate the default data segment Alignment oan the desired alignment Any power of 2 to 256 2xx0 through is permissable Do not use zero to specify the desired alignment If the extended form of NEW is used both a segment and alignment must be specified there is no form which permits selective inclusion of either char
36. l is applicable only when e is of type long integer or subrange of integer or real If e is of type long or integer or subrange of integer then e2 indicates the base in which the value of e is to be printed The valid range for e2 is 2 36 and 36 2 If e2 is positive then the value of e is printed as a signed quantity 16 bit twos complement otherwise the value of e is printed as a full 16 bit unsigned quantity If e2 is omitted the signed value of e is printed in base 10 If e is of type real then e2 specifies the number of digits to follow the decimal point The number is then printed in fixed point notation If e2 is omitted then real numbers are printed in floating point notation 17 5 CLOSE The CLOSE intrinsic closes an output file The intrinsic has the following form CLOSE F F is the file variable to be associated with the file to be closed Note that if you do not close a file for which a rewrite was performed and the program exits or aborts the data is lost PERQ Pascal Extensions December 27 1983 18 Miscellaneous Intrinsics 18 1 StartIO STARTIO is a special QCode See the PERQ QCode Reference Manual which is used to initiate input output operations to raw devices Pascal supports a procedure SIARTIO to facilitate generation of the correct QCode sequence for 1 0 programming The procedure call has the following form STARTIO Unit where Unit is the hardware unit number of the devic
37. llowed by or then is assumed Note currently two programs the debugger and the disassembler use the information stored in the Name Table 19 2 8 Version Switch The Version Switch permits the inclusion of a version string in the first block of the SEG file This string has a maximum length of 80 characters Currently this string is not used by any other PERQ software however it may be accessed by user programs to PUE SEG files The format for this switch is VERSION lt string gt or VERSION lt string gt to set the Version string PERQ Pascal Extensions December 27 1983 When using the VERSION form of the switch the version string is terminated by the end of the comment or the end of the line If the comment exceeds a single line the remainder of the comment is ignored If the VERSION form is used the version string is terminated by either the end of the command line or the occurrence of a character hence a may not appear in the version string 19 2 9 Comment Switch The Comment Switch permits the inclusion of arbitrary text in the first block of the SEG file This string has a maximum length of 80 characters It is particularly useful for including copyright notices in SEG files The format for this switch is COMMENT lt string gt or COMMENT lt string gt to set the comment string When utilizing the COMMENT form of the switch the comment text is terminated by th
38. m lt nultiplying operator gt lt cfactor gt multiplying operator X DIV MOD AND cfactor unsigned constant constant expression gt CHR constant expression ORD constant expression RECAST constant expression type identifier WORDSIZE lt name gt NOT lt cfactor gt PERQ Pascal Extensions December 27 1983 5 Type Compatibility PERQ Pascal now supports strict type compatability as defined by the BSI ISO Pascal Standard BSI79 with one addition two strings regardless of their maximum static lengths are considered compatable 5 1 Type Coercion RECAST The function RECAST converts the type of an expression from one type to another type when both types require the same amount of space RECAST like the standard functions CHR and ORD is processed at compi le time and thus does not incur run time overhead The function takes two parameters the expression and the type name for the result Its declaration is function RECAST value expression type T result type name T The following is an example of its use program RecastDemo type color red blue yellow green var C color I integer 225 RECAST I color C red end Note that RECAST does not work correctly for all combinations of types use the RECASI function sparingly and always scrutinize the dard Generally only the following conversions produce expected result
39. r var W PtrPAOfChar begin W recast GenPtr PtrPAOfChar writeln W 1 W 2 end begin new I I 16961 First byte A second B Proci 1 C l1 C 121 D 1 end produces output AB CD 11 2 Generic Files Generic files have very restricted usage Their purpose is to provide a facility for passing various types of files to a single procedure or function Generic files may only appear as routine VAR parameters Their type is FILE They can be used in only two ways 1 Passed as a parameter to another generic file parameter or 2 As an argument to the LOADADR intrinsic 15 PERQ Pascal Extensions December 27 1983 The following examples show two ways of using generic files program P t var FOfInt file of integer F text F2 file of boolean procedure Procl var GenFile file var UseGenFile record case boolean of true FileOfInterest FOfInt false Offset integer Segment integer enc begin loadAdr GenF ile storexpr UseGenFile Offset storexpr UseGenF i 1e Segment Now FileOfInterest can be used end procedure Proc2 var GenFile file const SIDW 183 var FileOfInterest FOfInt begin loadAdr Fi leOf Interest loadAdr GernFile InLineByte SIDW Now FileOfInterest can be used _ 16 PERQ Pascal Extensions December 27 1983 12 Procedure Func
40. res and functions which are forward declared this includes EXPORT declarations and contain procedure parameters may not have their parameter lists redeclared at the site of the procedure body 5 The compiler currently permits the use of an EXIT statement where the routine to be exited from is at the same lexical level as the routine containing the EXIT statement For example program Quirk rocedure ProcOne gin end procedure ProcTwo gin exit ProcOne end begin ProcIwo end If there is no invocation of the routine to be 44 PERQ Pascal Extensions December 27 1983 exited on the run time stack the PERQ hangs and must be re booted 6 The filename specification given in IMPORTS Declarations must start with an alphabetic character 7 Record comparisons involving acked records illegal comparisons will not be caught unless the word PACKED appears explicitly in the record definition For example records with fields of user defined type Foo where Foo contains packed information are considered comparable by the compiler when in actuality they are not 8 Reals and longs cannot be used together in an expression 9 The compiler will not detect an error in the definition or use of a set that exceeds set size limitations If such a set is used incorrect code will be generated 10 Many functions that exist for integers for example LAND are not implemented for longs Also you can only us
41. s longs reals and pointers to any other type arrays and records to either arrays or records sets of 0 n to any other type constants to long or real one word types except sets to one word types except sets Avoid the use of the RECAST function for any other conversion WARNING successful compilation does NOT imply that the RECAST function will execute correctly PERQ Pascal Extensions December 27 1983 6 Extended Case Statement Two extensions have been made to the case statement 1 Constant subranges as labels 2 The otherwise clause which is executed if the case selector expression fails to match any case label Case labels may not overlap A compile time error occurs if any label has multiple definitions The extended syntax for the case statement is case statement CASE expression OF case list element case list element END case list element case label list statement empty case label list case label case label case label constant constant OTHERWISE If the selector expression is not in the list of case labels and no OTHERWISE label is used then the case statement is a no op This is different from PASCAL as defined by the PASCAL User Manual and Report which suggests that this be a fault PERQ Pascal Extensions December 27 1983 7 Control Structures 7 1 EXIT Statement The procedure EXIT allows
42. t is the name of a compiler switch All compiler switches specified on the command line must begin with the character Any number of switches may be specified and if a switch is specified multiple times the last occurrence is used Also if the HELP switch is specified the other information on the command line is ignored The available switches are defined in the following sections The interface to the compiler is slightly different when invoked from a command file If there is an error in the command line it does not prompt for input but rather logs an entry in a file called CmdF i lePascal ERR in the local directory If this file does not exist in the local directory the compiler creates the file and inserts the entry Otherwise the compiler simply appends the entry to existing file The never deletes this file PERQ Pascal Extensions December 27 1983 19 2 Compiler Switches PERQ Pascal compiler switches may be set either in a mode similar to the convention described on pages 100 102 of PASCAL User Manual and Report JW74 or on the command line described above see above Section Command Line The first form of compiler switches may be written as comments and are designated as such by a dollar sign character as the first character of the comment followed by the switch unique abbreviations are acceptable and possibly switch parameters The second form is given after the input file specificat
43. the entire string the dynamic length of the string will be set to the number of characters read 17 4 WRITE WRITELN PERQ Pascal By PASCAL many extensions to the WRITE and WRITELN procedures defined by PASCAL User Manual and Report JW 4 Due to the scope of these extensions the WRITE and WRITELN procedures are completely redefined below 1 2 write pl pn stands for write output pl pn write f pl pn stands for BEGIN write f pl write f pn END writeln pl pn stands for writeln output pl pn writeln f pl pn stands for BEGIN write f pl write f pn writeln f END 5 Every parameter pi must be of one of the forms el e el e2 where e el and e2 are expressions 6 e is the VALUE to be written and may be of k EA pa long integer or subrange of integer real lean packed array of char or string For parameters of type boolean one of the strings TRUE FALSE or UNDEF will be written UNDEF is written if the internal form of the expression is neither O nor 1 7 el the minimum field width is optional In general the value e is written with el characters with preceding blanks With one exception if el is smaller than the number of characters required to print the given value more space is allocated if e is a packed array of char then only the first el characters of the array are printed 28 PERQ Pascal Extensions December 27 1983 8 e2 which is optiona
44. the size of memory For systems with 256k bytes of main memory the default number of symbol table blocks is 24 and the maximum number of symbol table blocks is 32 Note that you can specify more than 32 symbol table blocks with a 256k byte system but performance usually degrades considerably For systems with 512k or 1024k bytes of main memory the default number of symbol table blocks is 200 and the maximum number of symbol table blocks is also 200 mE PERQ Pascal Extensions December 27 1983 19 2 6 Automatic RESET REWRITE The PERQ Pascal compiler automatically generates a RESET INPUT and REWRITE OUTPUT This may be disabled if desired with the use of the AUTO switch The format for this switch is Default value Automatic initialization enabled GAUTO or AUTO enables automatic initialization AUTO or NOAUIO disables automatic initialization If SAUTO is not followed by a or then is assumed If the comment form of this switch is used it must precede the BEGIN of the main body of the program 19 2 7 Procedure Function Names The PERQ Pascal compiler generates a table of the procedure and function names at the end of the SEG file if so directed This table may be useful for debugging programs The format for this switch is Default value Name Table is generated NAMES or NAMES enables generation of the Name Table NAMES or NONAMES disables generation of the Name Table If NAMES is not fo
45. ting file to be read and Name is a string containing the name of the file to be read The current file position is set to the beginning of file i e RESET assigns the value of the first element of the file to F EOF F becomes false if F is not empty otherwise EOF F becomes true and F is undefined 17 3 READ READLN PERQ Pascal supports extended versions of the READ and READLN procedures defined by PASCAL User Manual and Report JW74 Along with the ability to read longs integers and subranges of integers reals and characters PERQ Pascal also supports reading booleans packed arrays of characters and strings The strings TRUE and FALSE or any unique abbreviations are valid input for parameters of type boolean Mixed upper and lower case are permissible If the parameter to be read is a PACKED ARRAY m n of CHAR then the next n m 1 characters from the input line will be used to fill the array If there are fewer than n m 1 characters on the line the array will be filled with the available characters starting at the m th position and the remainder of the array will be filled with 27 PERQ Pascal Extensions December 27 1983 blanks If the parameter to be read is of type STRING then the string variable will be filled with as many characters as possible until either the end of the input line is reached or the maximum length of the string is met If there are not enough charact rs on the line to fill
46. tion LXOR Vali Val2 integer integer LXOR returns the bitwise EXCLUSIVE OR of Vall and Val2 16 5 Shift Function SHIFT Value Distance integer integer SHIFT returns Value shifted Distance bits If Distance is positive a left shift occurs otherwise a right shift occurs When performing a left shift the Least Significant Bit is filled with a O and likewise when performing a right shift the Most Significant Bit is filled with a O 25 PERQ Pascal Extensions December 27 1983 16 6 Rotate Function ROTATE Value Distance integer integer ROTATE returns Value rotated Distance bits to the right ROTATE accepts only a positive integer in the range 0 through 15 for A m Note that the direction of the ROTATE is the opposite of 26 PERQ Pascal Extensions December 27 1983 17 Input Output Intrinsics PERQ s Input Output intrinsics vary slightly from PASCAL User Manual and Report JW74 17 1 REWRITE The REWRITE procedure has the following form REWRITE F Name F is the file variable to be associated with the file to be written and Name is a string containing the name of the file to be created EOF F becomes true and a new file may be written The only difference between the PERQ and PASCAL User Manual and Report JW74 REWRITE is the inclusion of the filename string 17 2 RESET The RESET procedure has the following form RESET F Name F is the file variable to be associated with the exis
47. tion Parameter Types 12 1 Parameter Lists PERQ Pascal permits but does not require the parameter list of procedures and functions which have been forward declared to be repeated at the site of the actual declaration If given the parameter list must match the previous declaration or compilation error occurs For redeclaration of function parameters both the parameter list and the function type must be repeated 12 2 Function Result Type PERQ Pascal functions may return any type with the exception of type FILE 12 3 Procedures and Functions as Parameters PERQ Pascal supports passing procedures and functions as parameters to other procedures or functions as described by the BSI ISO Pascal Standard BSI79 You must put the full description of the procedure parameter in the routine header just as if it was defined by itself For example Procedure EnumerateAll directory String Function for each one filename String boolean all boolean Note that if the procedure is forward declared or in an export section the routine header for this procedure cannot be repeated Edge x PERQ Pascal Extensions December 27 1983 13 Modules The module facility provides the ability to encapsulate procedures functions data and types as well as supporting separate compilation Modules may be separately compiled and intermodule type checking will be performed as part of the compilation process Unless an identifier is as eode
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