9 ms·

As pointed out in the comments in the article, these kinds of logic puzzles are easier to solve using constraint programming than "regular" logic programming.

• YeGoblynQueenne 3y ago
  To clarify, CLP((Z) does not stand for "Constraint Logic Programming for the Zebra puzzle" :P
• tannhaeuser 3y ago
  How is that "easier" than the following straightforward Prolog code? zebra(Houses) :- houses(Houses), member(house(red, english, _, _, _), Houses), member(house(_, spanish, dog, _, _), Houses), member(house(green, _, _, coffee, _), Houses), member(house(_, ukrainian, _, tea, _), Houses), right_of(house(green,_,_,_,_), house(ivory,_,_,_,_), Houses), member(house(_, _, snails, _, winstons), Houses), member(house(yellow, _, _, _, kools), Houses), Houses = [_, _, house(_, _, _, milk, _), _,_], Houses = [house(_, norwegian, _, _, _)|_], next_to(house(_,_,_,_,chesterfields), house(_,_,fox,_,_), Houses), next_to(house(_,_,_,_,kools), house(_,_,horse,_,_), Houses), member(house(_, _, _, orange_juice, lucky_strikes), Houses), member(house(_, japanese, _, _, parliaments), Houses), next_to(house(_,norwegian,_,_,_), house(blue,_,_,_,_), Houses), member(house(_, _, zebra, _, _), Houses), member(house(_, _, _, water, _), Houses). houses([ house(_, _, _, _, _), house(_, _, _, _, _), house(_, _, _, _, _), house(_, _, _, _, _), house(_, _, _, _, _)]). right_of(A, B, [B, A | _]). right_of(A, B, [_ | Y]) :- right_of(A, B, Y). next_to(A, B, [A, B | _]). next_to(A, B, [B, A | _]). next_to(A, B, [_ | Y]) :- next_to(A, B, Y). member(X, [X|_]). member(X, [_|Y]) :- member(X, Y). ?- zebra(Houses) To check it out yourself, copy/paste this into https://quantumprolog.sgml.io/browser-demo/browser-demo.html https://quantumprolog.sgml.io/browser-demo/browser-demo.html and execute on your browser.
  • Jtsummers 3y ago
    solution(Pairs, Water, Zebra, Vs) :- Table = [Houses,Nations,Drinks,Smokes,Animals], Houses = [Red,Green,Yellow,Blue,Ivory], Nations = [England,Spain,Ukraine,Norway,Japan], Names = [england,spain,ukraine,norway,japan], Drinks = [Coffee,Milk,OrangeJuice,Tea,Water], Smokes = [OldGold,Kools,Chesterfield,LuckyStrike,Parliaments], Animals = [Dog,Snails,Horse,Fox,Zebra], pairs_keys_values(Pairs, Nations, Names), maplist(all_distinct, Table), append(Table, Vs), Vs ins 1..5, England #= Red, % hint 1 Spain #= Dog, % hint 2 Coffee #= Green, % hint 3 Ukraine #= Tea, % hint 4 Green #= Ivory + 1, % hint 5 OldGold #= Snails, % hint 6 Kools #= Yellow, % hint 7 Milk #= 3, % hint 8 Norway #= 1, % hint 9 next_to(Chesterfield, Fox), % hint 10 next_to(Kools, Horse), % hint 11 LuckyStrike #= OrangeJuice, % hint 12 Japan #= Parliaments, % hint 13 next_to(Norway, Blue). % hint 14 next_to(H, N) :- abs(H-N) #= 1. It's subjective, but the above is far clearer about the rules to me. Compare `next_to` in both: next_to(Kools, Horse) next_to(house(_,_,_,_,kools), house(_,_,horse,_,_), Houses) The former is much more straightforward as a representation of the hint. You don't need to know which entry in a `house` corresponds to cigarette brand and animal, you can just directly compare the two and say Kools is next to Horse.