A Prolog solver for the Zebra puzzle a.k.a. Einstein's riddle

einstein.pl

% A Prolog solver for the Zebra puzzle a.k.a. Einstein's riddle.
% https://en.wikipedia.org/wiki/Zebra_Puzzle

einstein :-
    einstein(Solution),
    write_sol(Solution).

einstein(Sol) :-
    Sol = [ 
        [1,N1,C1,P1,D1,S1],                             % There are five houses.
        [2,N2,C2,P2,D2,S2],
        [3,N3,C3,P3,D3,S3],
        [4,N4,C4,P4,D4,S4],
        [5,N5,C5,P5,D5,S5]],
    member([_,englishman,red,_,_,_],Sol),               % The Englishman lives in the red house.
    member([_,spaniard,_,dog,_,_],Sol),                 % The Spaniard owns the dog.
    member([_,_,green,_,coffee,_],Sol),                 % Coffee is drunk in the green house.
    member([_,ukrainian,_,_,tea,_],Sol),                % The Ukrainian drinks tea.
    member([GH,_,green,_,_,_],Sol),                     % The green house is immediately to the right of the ivory house.
    member([IH,_,ivory,_,_,_],Sol),
    GH =:= IH + 1,
    member([_,_,_,snails,_,old_gold],Sol),              % The Old Gold smoker owns snails.
    member([_,_,yellow,_,_,kools],Sol),                 % Kools are smoked in the yellow house.
    member([3,_,_,_,milk,_],Sol),                       % Milk is drunk in the middle house.
    member([1,norwegian,_,_,_,_],Sol),                  % The Norwegian lives in the first house.
    member([BH,_,_,_,_,chesterfields],Sol),             % The man who smokes Chesterfields lives in the house next to the man with the fox.
    member([CH,_,_,fox,_,_],Sol),
    next_to(BH,CH),
    member([DH,_,_,_,_,kools],Sol),                     % Kools are smoked in the house next to the house where the horse is kept.
    member([HH,_,_,horse,_,_],Sol),
    next_to(DH,HH),
    member([_,_,_,_,orange_juice,lucky_strike],Sol),    % The Lucky Strike smoker drinks organge juice.
    member([_,japanese,_,_,_,parliaments],Sol),         % The Japanese smokes Parliaments
    member([NH,norwegian,_,_,_,_],Sol),                 % The Norwegian lives next to the blue house.
    member([BlH,_,blue,_,_,_],Sol),
    next_to(NH,BlH),
    permutation([englishman,spaniard,ukrainian,japanese,norwegian],[N1,N2,N3,N4,N5]),
    permutation([green,ivory,yellow,blue,red],[C1,C2,C3,C4,C5]),
    permutation([dog,snails,fox,horse,zebra],[P1,P2,P3,P4,P5]),
    permutation([coffee,tea,milk,orange_juice,water],[D1,D2,D3,D4,D5]),
    permutation([old_gold,kools,chesterfields,lucky_strike,parliaments],[S1,S2,S3,S4,S5]).

next_to(A,B) :- A =:= B - 1.
next_to(A,B) :- A =:= B + 1.

write_sol(Solution) :-
    write('+--+------------+------------+------------+-------------+--------------+'),nl,
    maplist(writef('|%2L|%12L|%12L|%12L|%13L|%14L|\n'),Solution),
    write('+--+------------+------------+------------+-------------+--------------+'),nl.