问题描述
假设我有以下事实:
boy(a).
boy(b).
girl(c).
girl(d).
如果我查询:
?-boy(X).
我明白了:
X=a;
X=b.
我应该使用哪个查询使用变量来获取不符合规则 boy() 的对象，在本例中为 c 和 d?
Which query should I use using a variable to get the objects that do not comply with the rule boy(), in this case, c and d?
我是 Prolog 的新手，所以我在考虑使用
I am new to Prolog, so I was thinking about using
?-not(boy(X)).
但这并不正确.我正在使用 swi-prolog.提前感谢您抽出宝贵时间和帮助.
But that is not correct. Im using swi-prolog.Thanks in advance for your time and help.
推荐答案
not(boy(X)) 的问题在于 Prolog 不知道可能选择的世界"是什么对于 X 以便然后测试他们是否是男孩.boy 事实当然只知道男孩.
The problem with not(boy(X)) is that Prolog doesn't know what the "universe of possible choices" are for X in order to then test if they're a boy. The boy facts only know boys, of course.
一种方法是定义除性别之外的所有人.例如:
One approach is to define all people in addition to the gender. For example:
% Define people
person(a).
person(b).
person(c).
person(d).
% Define genders
boy(a).
boy(b).
girl(c).
girl(d).
然后检查所有非男孩"，你会这样做:
Then to check for all "non-boys" you would do:
?- person(X), not(boy(X)).
根据您想要如何组织数据，您可以将性别与人相结合:
Depending upon how you want to organize your data, you can combine gender with person:
person(a, boy).
person(b, boy).
person(c, girl).
person(d, girl).
然后查询:
?- dif(Y, boy), person(X, Y).
或者把它写成谓词:
person_not_of_gender(Person, Gender) :-
dif(OtherGender, Gender),
person(Person, OtherGender).
然后查询:
?- person_not_of_gender(Person, boy).
这篇关于Prolog:获取一个或多个不符合事实的对象的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！