6.2.8 Foreign Code Examples

Given: a Prolog file ex.pl and a C file ex.c shown below.

                                      
ex.pl
     
     foreign_resource(ex, [c1, c2, c11, c21, c3, c4, c5, c6]).
     
     foreign(c1,  c, c1(+integer, [-integer])).
     foreign(c2,  c, c2(-integer)).
     foreign(c11, c, c11(+atom, [-atom])).
     foreign(c21, c, c21(+atom, -atom)).
     foreign(c3,  c, c3(+float, [-float])).
     foreign(c4,  c, c4(-float)).
     foreign(c5,  c, c5(+string,[-string])).
     foreign(c6,  c, c6(-string)).
     
     :- load_foreign_resource(ex).

                                       
ex.c
     
     #include <sicstus/sicstus.h>
     /* ex_glue.h is generated by splfr from the foreign/[2,3] facts.
        Always include the glue header in your foreign resource code.
     */
     #include "ex_glue.h"
     
     /* c1(+integer, [-integer]) */
     long int c1(a)
     long int a;
     {
        return(a+9);
     }
     
     /* c2(-integer) */
     void c2(a)
     long int *a;
     {
        *a = 99;
     }
     
     /* c11(+atom, [-atom]) */
     SP_atom c11(a)
     SP_atom a;
     {
        return(a);
     }
     
     /* c21(+atom, -atom) */
     void c21(a,b)
     SP_atom a;
     SP_atom *b;
     {
        *b = a;
     }
     
     /* c3(+float, [-float]) */
     double c3(a)
     double a;
     {
        return(a+9.0);
     }
     /* c4(-float) */
     void c4(a)
     double *a;
     {
        *a = 9.9;
     }
     /* c5(string, [-string]) */
     char const * c5(a)
     char const * a;
     {
        return(a);
     }
     /* c6(-string) */
     void c6(a)
     char const * *a;
     {
        *a = "99";
     }

Dialog at the command level:

     % splfr ex.pl ex.c
     % sicstus -l ex
     % compiling /home/matsc/sicstus4/ex.pl...
     %  loading foreign resource /home/matsc/sicstus4/ex.so in module user
     % compiled /home/matsc/sicstus4/ex.pl in module user, 0 msec 3184 bytes
     SICStus 4.1.2 ...
     Licensed to SICS
     | ?- c1(1,X1), c2(X2), c11(foo,X11), c21(foo,X21), c3(1.5,X3), c4(X4), c5(foo,X5), c6(X6).
     X1 = 10,
     X2 = 99,
     X3 = 10.5,
     X4 = 9.9,
     X5 = foo,
     X6 = '99',
     X11 = foo,
     X21 = foo ? <RET>
     yes