How to negate in Prolog

问题

I'm new to PROLOG and am at the very beginning of the exercises on this page. Given the rules parent(X, Y) and male(X), I'm trying to define a rule mother(X, Y) as

mother(X, Y) :-
    not(male(X)),
    parent(X, Y).

However, in GNU Prolog I get the following error:

| ?- mother(lina, julia).
uncaught exception: error(existence_error(procedure,not/1),mother/2)
| ?- 

回答1:

\+/1 is the ISO Prolog predicate to "negate". Note that "negate" means here not provable at that point.

You can refer to this excellent answer by @false for more on the subject

回答2:

The solution is actually in the exercise file on that page:

female(X) :- \+ male(X).

As @Mog said, negation is the unary \+ operator.

来源：https://stackoverflow.com/questions/10141600/how-to-negate-in-prolog