HP SunSoft Pascal 4.0 Bedienungsanleitung PDF herunterladen (Seite 155)

100

101

The C–Pascal Interface 131

Parameters That Are Pointers to Procedures

Pascal has a special type that is a pointer to a procedure. A variable of this

type can be used as a parameter, as follows:

The C function, RetReal.c double RetReal(double *x)

{

return(*x + 1.0);

}

The Pascal main program,

RetRealMain.p

program RetRealMain;

var

r, s: real;

function RetReal(var x: real): real; external c;

begin

r := 2.0;

s := RetReal(r);

writeln(r: 4: 1, s: 4: 1)

end. { RetRealMain }

The commands to compile and

execute RetReal.c and

RetRealMain.p

hostname% cc -c RetReal.c

hostname% pc RetReal.o RetRealMain.p

hostname% a.out

2.0 3.0

The C function, ProcPar.c #include <string.h>

void proc_c (void (*p)()) /* a pointer to procedure argument */

{

char *s ;

s = "Called from C";

(*p)( s, strlen(s)); /* Call the Pascal routine */

}

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