Prolog 序言无限重复相同的答案
以下是我的事实:Prolog 序言无限重复相同的答案,prolog,infinite-loop,Prolog,Infinite Loop,以下是我的事实: 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
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)时,它会无限地返回相同的答案
?- 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 ? ;
我如何阻止它重复,因为当另一个规则调用父规则时,它会崩溃prolog您的问题就在这里:
parent(X,Y):-
married(Z,X),
parent(Z,Y).
实际上,如果删除已婚/2
,您可以更清楚地看到它:
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