projog

3.2. fail - always fails.

The goal fail always fails.

Examples

?- fail.

no

a(1).
a(2).
a(3).

test :- a(X), a(Y), write(Y), write(' '), write(X), nl, fail.

?- test.
1 1
2 1
3 1
1 2
2 2
3 2
1 3
2 3
3 3

no