PREDICATE( name, arity )

Suppose I have the program below:

Code:

---

    #include files

    PREDICATE( add, 3 )
    {
        return A3 = (long)A1 + (long)A2;
    }

    int main( int argc, char** argv )
    {
        PlEngine e( argv[0] );
        PlCall( "consult('myFile.pl')" );
        PL_halt( PL_toplevel() ? 0 : 1 );
    }

---

When I compile it, it links Prolog and C++ and then launches the Prolog command prompt.

All I have in myFile.pl is

Code:

---

    :- use_module( library(shlib) ).

---

When I type listing at the Prolog prompt, I get

Code:

---

    Foreign: add/3

---

So far, everything is simple and as expected. My question is how do I use the result of some other subroutine, say a class, in my foreign predicate add? Let's say I have a class somewhere in my program that calculates some x and y. Obviously x and y would be private or protected members of that class' header file. How do I use x and y in my add predicate? For instance, if I wanted to return the sum of x and y and first and second arguments of add?

Cheers,

well the you can a member fucntion which your calls to get the private or the protected data member. There is no difference in that. You program what ever you want in C++ and then use your Prolog API and warp it up which then provides a neat way of interfacing it between the prolog and C/C++.

I suppose you know how to get the results in prolog?

Code:

---

add( 10,20, R ).

---

The R variable would hold the sum of 10 and 20 as Prolog wouldn't return the sum instead instead true/false.

ssharish