fail/0

fail

Will invoke backtracking.

Remarks

fail forces failure of a predicate and, hence, always causes backtracking.

In a clause ended with a fail, it is not necessary to bind the output arguments for the clause.

Example

person("Leo","Copenhagen").

person("Victor","St.Petersburg").

print_all():-

person(Name,Addr),

write("\nName=",Name,", Address=",Addr),

fail.