CODEWITHSUNDEEP
prolog
omega
omega

Reputation: 43833

How to force a fail in Prolog?

In prolog, is it possible to force a fail? Something like:

check(F,A,[1,2,3]) :- FAIL.
check(F,A,_) : greater_than(F,A).

This may be a bad example, but something along the lines of this.

So if it does a pattern match on F,A,[1,2,3], then we just stop the who unifying process, and return a false.

Upvotes: 0

Views: 2088

Answers (1)

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726499

Prolog has a built-in fail/0 predicate, which always fails. You need a cut ! in front of it in order to prevent further matching of the same check/3 rule:

check(F,A,[1,2,3]) :- !, fail.

Upvotes: 1

Related Questions