ISO Pascal reference manual

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Chapter 6 status := GetGlobalString IF status < 0 THEN ELSE (sys_ver, 128, sys_ver_len, 'SYS$Version 11); WriteLn ('Couldn't get system version...'); BEGIN Write ('System version: '); FOR j := 1 TO sys_ver_len DO Write (sys_ver[j]); END; WriteLn 2. Calling a Fortran Function from Pascal (refer to the Acorn 32000 Fortran 77 Reference Manual). An integer function FNC with two integer parameters written in Fortran might be referenced from Acorn 32000 (extended) Pascal as: TYPE IntRef =IInteger; FNCParams = RECORD p1, p2 : IntRef END; FNCParamsRef =IFNCParams; IMPORT FUNCTION FNC (p: FNCParamsRef): IntRef; and used as: PROCEDURE LocaIFNC (n1, n2: Integer): Integer; VAR rp: IntRef; (NB rp does not point into heap, ) ( so no NEW/DISPOSE param: FNCParamsRef; BEGIN NEW (param); WITH paramiDO BEGIN NEW (p1); NEW (p2); p11 := a; p21 := b; rp := FNC (param); DISPOSE (p1); DISPOSE (p2) END; DISPOSE (param); 42 Pascal Issue I
END; LocaIFNC = rip.; Idereference for F77 result) Using Pascal with other languages (N.B. As described in section 6.2.2 it is necessary to compile this code with assignment checks disabled, otherwise the reference to the Fortran result variable via a Pascal pointer will probably fail since the result variable will not have been allocated on the Pascal heap.) This is the obvious logical method of interfacing the procedure, but is by no means the most efficient way of calling a Fortran function! The main problem is that the only (legal) way of using pointers in standard Pascal is in claiming, accessing and disposing of heap memory via NEW, DISPOSE etc. - it is not possible to point pointers at normal local variables. In the above example some improvement would obtain by specifying FNC as taking a VAR parameter of type FNCParams, rather than a pointer to such a structure - VAR parameters are implemented by the same mechanism in low-level terms. Thus: IMPORT FUNCTION FNC (VAR p: FNCParams): IntRef; PROCEDURE LocaIFNC (n1, n2: Integer): Integer; VAR rp: IntRef; paramBlock: FNCParams; BEGIN WITH paramBlock DO BEGIN NEW (p1); NEW (p2); p1l := n1; p21 := n2; rp := FNC (paramBlock); DISPOSE (p1); DISPOSE (p2) END; LocalFNC = rpt; END; If the function is to be called more than once, it might be worthwhile removing the calls on NEW and DISPOSE from the procedure, since these involve an amount of heap management activity. This could be done by making the parameter block a global variable, and claiming the space for the parameters (via p1 and p2) only once, before the first call on LocalFNC was made. Thus we would arrive at: Pascal Issue 1 43
Page 1: ISO PASCAL
Page 4 and 5: © Copyright Acorn Computers Limite
Page 6 and 7: 5 Errors and debugging 21 5.1 Compi
Page 8 and 9: Chapter 1 1.2.1 Installation The Pa
Page 10 and 11: Chapter 2 recognise any of the exte
Page 13 and 14: 3 A Description of ISO Pascal 3.1 L
Page 15 and 16: Reference token Alternative token 1
Page 17 and 18: 3.3 Extensions to ISO 7185 A Descri
Page 19 and 20: $INCLUDE 'a-file-name' The lines in
Page 21: MODULE example; EXPORT counter : in
Page 24 and 25: Chapter 4 (6.9.3.1) The default val
Page 26 and 27: Chapter 4 4.3.8 Modules There are n
Page 28 and 29: Chapter 5 non-occurrence of this me
Page 30 and 31: Chapter 5 PROGRAM warn(output); LAB
Page 32 and 33: Chapter 5 PROGRAM warn(output); VAR
Page 34 and 35: Chapter 5 product := this * that; *
Page 36 and 37: Chapter 5 An example of a Pascal ru
Page 38 and 39: Chapter 6 The form `x x x x' will b
Page 40 and 41: Chapter 6 byte-aligned, is allocate
Page 42 and 43: Chapter 6 END; 6.2.3 Parameters I a
Page 44 and 45: Chapter 6 Subrange Parameters of su
Page 46 and 47: Chapter 6 5. For all results other
Page 50 and 51: Chapter 6 TYPE IntRef =tInteger; FN
Page 52 and 53: Chapter 6 ; fetch the result via th
Page 54 and 55: *ERROR 6 -- an illegal space has be
Page 56 and 57: *ERROR 13 -- PACKED is not permitte
Page 58 and 59: *ERROR 21 -- has been used in its
Page 60 and 61: PROGRAM fail; PROCEDURE Lost; FORWA
Page 62 and 63: patterns (integer values); if the e
Page 64 and 65: PROGRAM fail(output); CONST one = 1
Page 66 and 67: PROGRAM fail; VAR f:FILE OF integer
Page 68 and 69: PROGRAM fail(output); BEGIN END. wr
Page 70 and 71: *ERROR 57 -- the objects in the set
Page 72 and 73: PROGRAM fail; TYPE ok = (red, yello
Page 74 and 75: PROGRAM fail(output); FUNCTION two:
Page 76 and 77: BEGIN END. s := f; *ERROR 72 -- the
Page 78 and 79: *ERROR 78 -- values of incompatible
Page 80 and 81: PROGRAM fail(input, output); TYPE t
Page 82 and 83: *ERROR 88 -- the item used to selec
Page 84 and 85: *ERROR 93 -- the name of the contro
Page 86 and 87: END. FOR w := sun TO fri DO writeln
Page 88 and 89: *ERROR 104 -- this statement requir
Page 90 and 91: *ERROR 111 PRED needs a parameter o
Page 92 and 93: END. thing(x); [x is not an integer
Page 94 and 95: BEGIN END. show; [parameter needed
Page 96 and 97: test(r.x); (r.x is a case selector}
Page 98 and 99:
PROGRAM fail(output); PROCEDURE try
Page 100 and 101:
*ERROR 137 -- the array has been gi
Page 102 and 103:
PROGRAM fail; VAR p : PACKED ARRAY
Page 104 and 105:
PROGRAM fail; [this needs the EXTEN
Page 106 and 107:
*FATAL ERROR 152 -- the compiler ca
Page 109 and 110:
Appendix C Execution errors *Execut
Page 111 and 112:
*Execution error -- significance lo
Page 113 and 114:
*Execution error -- NIL pointer use
Page 115 and 116:
*Execution error -- reset on non-ex
Page 117 and 118:
PROGRAM error(output); VAR f : text
Page 119:
Index C M Case 8 Machine code / Com
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