C Interface

If the C file c.c is compiled as shown below, then loading the Prolog file as shown will produce the indicated results.

                                        
c.c
     
     
     /* 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]) */
     QP_atom c11(a)
     QP_atom a;
     {
        return(a);
     }
     
     /* c21(+atom, -atom) */
     void c21(a,b)
     QP_atom a;
     QP_atom *b;
     {
        *b = a;
     }
     
     /* c3(+float, [-float]) */
     double c3(a)
     double a;
     {
        return(a+9.0);
     }
     /* c4(-float) */
     void c4(a)
     float *a;
     {
        *a = 9.9;
     }
     /* c5(string, [-string]) */
     char * c5(a)
     char * a;
     {
        return(a);
     }
     /* c6(-string) */
     void c6(a)
     char * *a;
     {
        *a = "99";
     }
     

At the command level:

     % cc -c c.c
     

Produces the object file.

                                       
c.pl
     
     
     foreign_file(c, [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_files([c], []),
        abolish(foreign_file,2),
        abolish(foreign,3).
     

Loading the Prolog file (see the reference pages for foreign/3, foreign_file/2 and load_foreign_files/2) into Prolog and invoking the following query gives the following results:

     | ?- 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,
     X11 = X21 = X5 = foo,
     X3 = 10.5,
     X4 = 9.89999,
     X6 = '99' ;
     
     
     no