% multOfFive4.pl: Final version!  The addition of "X>0" cuts off
% the infinite recursion when users ask the search to continue.
% X falling below 0 will cause the "X>0" predicate fail, and
% therefore the rule to fail, without running out of stack space. 

multipleOf5(0).
multipleOf5(X) :- X > 0, Y is X-5, multipleOf5(Y).