logru 0.4.1

A small, embeddable and fast interpreter for a subset of Prolog.
Documentation 
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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, england, _, _, _), Houses),
  exists(house(_, spain, _, _, dog), Houses),
  exists(house(_, japan, _, painter, _), Houses),
  exists(house(_, italy, tea, _, _), Houses),
  first(house(_, norway, _, _, _), Houses),
  rightOf(house(green, _, _, _, _), house(white, _, _, _, _), Houses),
  exists(house(_, _, _, photographer, snails), Houses),
  exists(house(yellow, _, _, diplomat, _), Houses),
  middle(house(_, _, milk, _, _), Houses),
  exists(house(green, _, coffee, _, _), Houses),
  nextTo(house(_, norway, _, _, _),house(blue, _, _, _, _), Houses),
  exists(house(_, _, juice, violinist, _), Houses),
  nextTo(house(_, _, _, physician, _),house(_, _, _, _, fox), Houses),
  nextTo(house(_, _, _, diplomat, _),house(_, _, _, _, horse), Houses),
  exists(house(_, _, water, _, _), Houses),
  exists(house(_, _, _, _, zebra), Houses).