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


% first base clause

dislikes_topping([], _, _):- !.

% second base clause

dislikes_topping([P|_], Top, yes):-
        dislikes(P, Top), !.

% step clause

dislikes_topping([_|Ps], Top, IsNo) :- 
        dislikes_topping(Ps, Top, IsNo).