Calling FORTRAN 77 from HP Pascal

The table and example in this section assume that the HP Pascal program and the FORTRAN 77 routine that it calls are both compiled in Native Mode. If the FORTRAN 77 routine is in a Compatibility Mode SL instead, you must write a switch stub to access it from your HP Pascal program (see “Switch Stubs ”).

Table 9-3 “Corresponding HP Pascal and FORTRAN 77 or FORTRAN 66/V Types ” matches corresponding HP Pascal and FORTRAN 77 or FORTRAN 66/V types. (It contains only the types that are acceptable for formal intrinsic parameters.) The variable n is an integer.

Table 9-3 Corresponding HP Pascal and FORTRAN 77 or FORTRAN 66/V Types

HP Pascal Type	Corresponding FORTRAN 77 or FORTRAN 66/V Type
`Array: Not PACKED`	An array of a corresponding type. (Pascal arrays are stored in row-major order; FORTRAN arrays are stored in column-major order.)
`Array: PACKED`	Not available
Boolean (false = 0, true = 1)	LOGICAL*1 (false = 0, true = 1)
Char	CHARACTER
Enumeration	Not available
File	Not available
Function	Function³
Function parameter or variable	Not available
Integer	INTEGER*4
Longreal	REAL*8 or DOUBLE PRECISION
PAC of `n` characters	CHARACTER*`x, x` in 1..`n` ^1,2
Pointer	Not available
Procedure	Subroutine³
Procedure parameter or variable	Not available
Real	REAL or REAL*4
Record	Build equivalent record
Set	Not available
Shortint	INTEGER*2
String	CHARACTER()²
String[`n`]	CHARACTER()²
VAR parameter	Default parameter mechanism
RECORD real_part : real ; imaginary_part : real ; END ;	COMPLEX

Table 9-3 Notes

When you call a Pascal routine from a FORTRAN routine, use the FORTRAN directive $ALIAS in the FORTRAN compilation unit to specify a nonstandard calling sequence for the Pascal routine. Specify %REF for each character string parameter (the FORTRAN default for character strings is %DESCR). See the example in “How Non-Pascal Programs Call Pascal Routines”.

For calling FORTRAN 77 from Pascal only. In the FORTRAN 77 compilation unit, declare the parameter as CHARACTER*n or CHARACTER*(*). For a PAC type HP Pascal parameter, HP Pascal passes the address followed by the length. For either string type HP Pascal parameter, HP Pascal passes the address of the data part of the string followed by its current length. The current length is loaded from the length field. For example:

A FORTRAN 77 routine:

CHARACTER*40 FUNCTION F77_Func (Str1,Str2)
CHARACTER*80 Str1
CHARACTER*(*) Str2
...
RETURN
END

An HP Pascal program that calls the FORTRAN 77 routine:

TYPE
   Str40 = string[40] ;
   Pac80 = PACKED ARRAY [1..80] OF char ;
 
FUNCTION F77_Func (VAR Str1 : Pac80 ;
                   VAR Str2 : Str40) : Str40 ;
                  EXTERNAL FTN77 ;
VAR
   Vbl1, Vbl2 : Str40 ;
   Pac1 : Pac80 ;
BEGIN { main program }
...
Vbl2 := strrtrim(F77_Func(Vbl1,Pac1)) ;
...
END ;

This is not correctly implemented in FORTRAN 77.

Example

The Pascal program Pascal_Fort calls the external FORTRAN 77 routine FORTPRC.

Pascal program:

PROGRAM Pascal_Fort (input,output);
TYPE
   char_str = PACKED ARRAY [1..20] OF char;
VAR
   a_str : char_str;
   int1,
   int2,
   sum  : integer;
PROCEDURE fortprc (VAR cstr : char_str;
                   VAR inta : integer;
                   VAR intb : integer;
                   VAR total : integer); EXTERNAL FTN77;
BEGIN
   a_str := 'Add these 2 numbers:';
   int1 := 25;
   int2 := 15;
   writeln(a_str,int1,int2);
   fortprc(a_str,int1,int2,sum);
   writeln(a_str,sum);
END.

FORTRAN 77 routine:

SUBROUTINE FORTPRC(CSTR,INT1,INT2,SUM)
    INTEGER INT1, INT2, SUM
    CHARACTER CSTR*20
    SUM = INT1 + INT2
    CSTR = "SUM OF TWO NUMBERS: "
    RETURN
    END

Note that on HP-UX, you must compile this code with f77 +800 command-line option or the FORTRAN $HP9000_800 directive.

Calling FORTRAN 77 from HP Pascal

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