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我正在用 Prolog 编写一个家谱程序。这是我的规则:

father(X,Y):-male(X),parent(X,Y).
mother(X,Y):-female(X),parent(X,Y).
parent(X, Y) :- father(X, Y).
parent(X, Y) :- mother(X, Y).
ancestor(X,Y):-parent(X,Y).
ancestor(X,Y):-parent(X,Z),ancestor(Z,Y).
grandfather(X,Y):-male(X),parent(X,Z),parent(Z,Y).
grandMother(X,Y):-female(X),parent(X,Z),parent(Z,Y).
sibling(X,Y):-parent(Z,X),parent(Z,Y),X \= Y.
cousin(X,Y) :-ancestor(Z,X),ancestor(Z,Y),not(parent(Z,X)),not(parent(Z,X)),not(ancestor(X,Y)),not(ancestor(Y,X)).

但是,每当我查询“祖先”时,我都会收到错误消息:

1815KB of Code Space (025D0000--02795D90)
  Current hole: 4FE40000--80040000
%
% PC: user:parent/2 at clause 1
%   Continuation: prolog:$do_yes_no/2 at clause 2
%    512KB of Global Stack (029C2000--02A4207C)
%    1265384KB of Local Stack (02A55E4C--4FE10000)
%    0KB of Trail (4FE10004--4FE10044)
%    Performed 1 garbage collections
% All Active Calls and
%         Goals With Alternatives Open  (Global In Use--Local In Use)
%
%         user:parent/2 (512KB--1265384KB)
%         user:parent/2 (512KB--1265384KB)...
%      ...user:parent/2 (512KB--1265377KB)
%  .....
     ERROR!!
     RESOURCE ERROR- not enough stack

这也给“表亲”规则带来了问题,它给出了

%
%
% YAP OOOPS: likely bug in YAP, segmentation violation.
%
%

我的“祖先”规则可能做错了什么?

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1 回答 1

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说有一个事实:

male(adam).

如果现在查询:

parent(adam,cain).

然后它将评估:

parent(adam,cain) :-
    father(adam,cain).

现在father/2将进一步评估:

parent(adam,cain) :-
    father(adam,cain) :-
        male(adam),
        parent(adam,cain).

所以我们看到它陷入了一个无限循环:为了 validate/ground parent/2,它是根据 定义的parent/2,但没有进展:我们用完全相同的参数调用它。

所以Prolog会陷入这个无限循环。由于ancestor/2依赖parent/2,它遭受与相同的症状parent/2

尝试去除循环依赖。

于 2017-08-02T23:33:32.950 回答