theylike(cheese).
theylike(fancyspreads(madeof(liver,and,onions))).
theylike(fancyspreads(madeof(cheese))).
theylike(poisonedbacon).
lethal(poisonedbacon).
popularfood(X):-
	theylike(X),
	print(X),
	\+lethal(X).
popularfood(X):-
	lethal(X),
	\+theylike(X).
popularfood(X):-
	popularfood(X).