dislikes(sam, onions). 
dislikes(sam, greenpeppers). 
dislikes(parker, pepperoni). 
dislikes(parker, greenpeppers). 
dislikes(elizabeth, pepperoni). 
dislikes(elizabeth, eggplant). 
dislikes(fred, pepperoni).

dislikes3(Name, Topping, IsNo) :-
	dislikes(Name, Topping).

likes2([], Top, []).
likes2([H|T], Top, [X|Y]) :- 
	dislikes3(H, Top, X),
	likes2(T, Top, Y).

likes1(People, Topping, IsNo) :- likes2(People, Topping, IsNo).