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我想计算一个数字的阶乘。我的阶乘规则在 Prolog 文件中，我将它连接到 C++ 文件。有人可以告诉我将 C++ 连接到 Prolog 有什么问题吗？

my factorial.pl file:

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



my factorial.cpp file:

headerfiles

term_t tf;
term_t tx;
term_t goal_term;
functor_t goal_functor;

int main( int argc, char** argv )
{
    argv[0] = "libpl.dll";

    PL_initialise(argc, argv);

    PlCall( "consult('factorial.pl')" );

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

    tf = PL_new_term_ref();
    PL_put_integer( tf, nf );
    tx = PL_new_term_ref();

    goal_term = PL_new_term_ref();
    goal_functor = PL_new_functor( PL_new_atom("factorial"), 2 );
    rval = PL_cons_functor( goal_term, goal_functor, tf, tx );

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

我得到 Prolog 提示，这是最后一行的作用。但是我没有得到阶乘计算的结果，例如：

?-  factorial( 5, X ).
X = 120
true

我错过了什么？

谢谢，

4

2 回答 2

1 
# include files

term_t tf;
term_t tx;
term_t goal_term;
functor_t goal_functor;

int main( int argc, char** argv )
{
    argv[0] = "libpl.dll";
    PL_initialise( argc, argv );

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

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

    tf = PL_new_term_ref();
    PL_put_integer( tf, nf );
    tx = PL_new_term_ref();
    goal_term = PL_new_term_ref();
    goal_functor = PL_new_functor( PL_new_atom("factorial"), 2 );
    PL_cons_functor( goal_term, goal_functor, tf, tx );

    int fact;
    if( PL_call(goal_term, NULL) )
        {
            PL_get_integer( tx, &fact );
            cout << fact << endl;
        }
    else
        {
            PL_fail;
        }

    PL_halt( PL_toplevel() ? 0 : 1 );
}
于 2010-04-06T20:36:22.853 回答
0

我对 SWI Prolog–C/C++ 桥不是很熟悉，但是一旦定义了术语，您似乎并没有启动查询。在将事情交给 SWI-Prolog 之前，您需要使用PL_callor然后打印结果。PL_open_query

    PL_cons_functor( goal_term, goal_functor, tf, tx );
int nfactorial;
if (PL_call(goal_term, NULL)) {
    PL_get_integer(tx, &nfactorial);
    std::cout << "X = " << nfactorial << " ." << std::endl;
} else {
    PL_fail;
}
    PL_halt( PL_toplevel() ? 0 : 1 );

我不知道您是否可以设置goal_term为顶级查询。如果您希望通过调用来运行查询PL_toplevel，您可以将查询构建为字符串并将其作为参数向量中的“-t”参数传递给PL_initialize.

于 2010-04-06T00:34:52.910 回答