Prolog 无限重复相同的答案

Question

这些是我的事实：

married(man, widow).
married(father,daughter).
married(widow, man).
married(daughter,father).

parent(father, man).
parent(widow, daughter).
parent(man, bboy).

% here is the rule giving me problems,

parent(X,Y):-
   married(Z,X),
   parent(Z,Y).

当我运行 parent(X,Y) 它 returns 同样的答案无限地如此

  ?- parent(X,Y).

X = father
Y = man ? ;

X = widow
Y = daughter ? ;

X = man
Y = bboy ? ;

X = widow
Y = bboy ? ;

X = widow
Y = daughter ? ;

X = widow
Y = bboy ? ;

X = widow
Y = daughter ? ;

如何阻止它重复，因为当另一个规则调用父规则时它会崩溃 prolog

Answer 1

你的问题在这里：

parent(X,Y):-
    married(Z,X),
    parent(Z,Y).

其实去掉married/2:

可以看得更清楚一点

parent(X,Y):-
    parent(Z,Y).

这将导致无限递归。简单的做法是重命名规则或事实：

parent(father, man).
parent(widow, daughter).
parent(man, bboy).

parent_of(X, Y) :-
    married(Z, X),
    parent(Z, Y).

不再递归。

Prolog 无限重复相同的答案

Prolog repeating the same answer infinitely

prolog

infinite-loop