Prolog interpreter

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Rules

exists(A, list(A, _, _, _, _)).
exists(A, list(_, A, _, _, _)).
exists(A, list(_, _, A, _, _)).
exists(A, list(_, _, _, A, _)).
exists(A, list(_, _, _, _, A)).

rightOf(R, L, list(L, R, _, _, _)).
rightOf(R, L, list(_, L, R, _, _)).
rightOf(R, L, list(_, _, L, R, _)).
rightOf(R, L, list(_, _, _, L, R)).

middle(A, list(_, _, A, _, _)).

first(A, list(A, _, _, _, _)).

nextTo(A, B, list(B, A, _, _, _)).
nextTo(A, B, list(_, B, A, _, _)).
nextTo(A, B, list(_, _, B, A, _)).
nextTo(A, B, list(_, _, _, B, A)).
nextTo(A, B, list(A, B, _, _, _)).
nextTo(A, B, list(_, A, B, _, _)).
nextTo(A, B, list(_, _, A, B, _)).
nextTo(A, B, list(_, _, _, A, B)).

puzzle(Houses) :-
    exists(house(red, english, _, _, _), Houses),
    exists(house(_, spaniard, _, _, dog), Houses),
    exists(house(green, _, coffee, _, _), Houses),
    exists(house(_, ukrainian, tea, _, _), Houses),
    rightOf(house(green, _, _, _, _), house(ivory, _, _, _, _), Houses),
    exists(house(_, _, _, oldgold, snails), Houses),
    exists(house(yellow, _, _, kools, _), Houses),
    middle(house(_, _, milk, _, _), Houses),
    first(house(_, norwegian, _, _, _), Houses),
    nextTo(house(_, _, _, chesterfield, _), house(_, _, _, _, fox), Houses),
    nextTo(house(_, _, _, kools, _),house(_, _, _, _, horse), Houses),
    exists(house(_, _, orangejuice, luckystike, _), Houses),
    exists(house(_, japanese, _, parliament, _), Houses),
    nextTo(house(_, norwegian, _, _, _), house(blue, _, _, _, _), Houses),
    exists(house(_, _, water, _, _), Houses),
    exists(house(_, _, _, _, zebra), Houses).

solution(WaterDrinker, ZebraOwner) :-
    puzzle(Houses),
    exists(house(_, WaterDrinker, water, _, _), Houses),
    exists(house(_, ZebraOwner, _, _, zebra), Houses).

Query

Answers