toppings([topping(onions, _), topping(greenpeppers, _), topping(pepperoni, _), topping(eggplant, _), topping(mushrooms, _), topping(goatcheese, _)]).

pizza(Toppings).

order(People, pizza(Toppings)) :- pizza(Pizza), toppings(Toppings),
member(topping(onions, A), Toppings), check(People, onions, A),
member(topping(greenpeppers, , Toppings), check(People, greenpeppers, ,
member(topping(pepperoni, C), Toppings), check(People, pepperoni, C),
member(topping(eggplant, D), Toppings), check(People, eggplant, D),
member(topping(mushrooms, E), Toppings), check(People, mushrooms, E),
member(topping(goatcheese, F), Toppings), check(People, goatcheese, F).