Factorial in C++ and Prolog

I would like to work out a number's factorial. My factorial rule is in a Prolog file and I am connecting it to a C++ code. Can someone tell me what is wrong with my C++ interface please?

Code:

---

    % factorial.pl

    factorial( 1, 1 ):-
        !.
    factorial( X, Fac ):-
        X > 1,
        Y is X - 1,
        factorial( Y, New_Fac ),
        Fac is X * New_Fac.


    // factorial.cpp

    # headerfiles

    term_t t1;
    term_t t2;
    term_t goal_term;
    functor_t goal_functor;

    int main( int argc, char** argv )
    {
        argc = 4;

        argv[0] = "libpl.dll";
        argv[1] = "-G32m";
        argv[2] = "-L32m";
        argv[3] = "-T32m";

        PL_initialise(argc, argv);

        if ( !PL_initialise(argc, argv) )
            PL_halt(1);

        PlCall( "consult(swi('plwin.rc'))" );
        PlCall( "consult('factorial.pl')" );

        cout << "Enter your factorial number: ";
        long n;
        cin >> n;

        PL_put_integer( t1, n );
        t1 = PL_new_term_ref();
        t2 = PL_new_term_ref();
        goal_term = PL_new_term_ref();
        goal_functor = PL_new_functor( PL_new_atom("factorial"), 2 );
        PL_put_atom( t1, t2 );
        PL_cons_functor( goal_term, goal_functor, t1, t2 );

        PL_halt( PL_toplevel() ? 0 : 1 );
    }

---

Edited by moderator: Added code tags

You're going to have to give more information. Then someone who is familiar with your setup may be able to advise. The method of interfacing between C (or C++) and prolog is highly dependent on both the compiler and on the prolog interpreter.

Overwriting argc and argv (as you have done, before the prolog-related stuff) is often an effective way to crash a program. Better to set up your own local storage for argv, and pass that to PL_initialise().

It would probably be easier to write your own factorial function in C++, but I assume your purpose here is learning to interface with your prolog rather than avoiding coding in C++ (as interfacing to other languages is not trivial).

http://cboard.cprogramming.com/cplus...ead-first.html