I implemented Einstein Riddle in Prolog and I'm trying to find out who had a fish at home.
I can't find fault in this code and trace option is not helping with this problem ;)
Rules:
- Norwegian lives in first house
- The Englishman lives in a red house.
- The green house is located directly on the left side of the white house.
- Dane drink tea.
- Light smoker lives next to the breeders of cats.
- A resident of the yellow house smokes a cigar.
- German smokes a water-pipe.
- A resident of the center house drinks milk.
- Light smoker has a neighbor who drink the water.
- Smoke cigarettes without filter breeding birds.
- Swede bred dogs.
- The Norwegian lives next to the blue house.
- Breeder of horses lives next to the yellow house.
- Smoke menthol drink beer.
- In the green house they drink coffee.
Here is my code:
on_the_left(X, Y, N) :-
Y is X - 1,
+ Y < 1,
+ X > N.
next_to(X, Y, N) :-
( Y is X + 1;
Y is X - 1),
+ X > N,
+ Y > N,
+ X < 1,
+ Y < 1.
fish(Who) :-
Houses = [
house(1, _Color1, _From1, _Animal1, _Drink1, _Smoke1),
house(2, _Color2, _From2, _Animal2, _Drink2, _Smoke2),
house(3, _Color3, _From3, _Animal3, _Drink3, _Smoke3),
house(4, _Color4, _From4, _Animal4, _Drink4, _Smoke4),
house(5, _Color5, _From5, _Animal5, _Drink5, _Smoke5) ],
N is 5,
%-- hint 1
member(house(1, _, norway, _, _, _), Houses),
%-- hint 2
member(house(_, red, england, _, _, _), Houses),
%-- hint 3 - on_the_left
member(house(GREEN, green, _, _, _, _), Houses),
member(house(WHITE, white, _, _, _, _), Houses),
on_the_left(GREEN, WHITE, N),
%-- hint 4
member(house(_, _, denmark, _, tea, _), Houses),
%-- hint 5 - next_to
member(house(LIGHT, _, _, _, _, light), Houses),
member(house(CAT, _, _, cat, _, light), Houses),
next_to(LIGHT, CAT, N),
%-- hint 6
member(house(_, yellow, _, _, _, cigar), Houses),
%-- hint 7
member(house(_, _, germany, _, _, waterpipe), Houses),
%-- hint 8
member(house(3, _, _, _, milk, _), Houses),
%-- hint 9 - next_to
member(house(WATER, _, _, _, water, _), Houses),
next_to(LIGHT, WATER, N),
%-- hint 10
member(house(_, _, _, bird, _, nofilter), Houses),
%-- hint 11
member(house(_, _, sweden, dog, _, _), Houses),
%-- hint 12 - next_to
member(house(NORWAY, _, norway, _, _, _), Houses),
member(house(BLUE, blue, _, _, _, _), Houses),
next_to(NORWAY, BLUE, N),
%-- hint 13 - next_to
member(house(HORSE, _, _, horse, _, _), Houses),
next_to(HORSE, GREEN, N),
%-- hint 14
member(house(_, _, _, _, beer, menthol), Houses),
%-- hint 15
member(house(_, green, _, _, coffee, _), Houses),
%-- FINAL QUESTION - WHO LET THE FISH OUT?
member(house(_, _, _, fish, _, _), Houses),
member(house(_, _, Who, fish, _, _), Houses).
I tried a lot of combination but:
?- fish(Who).
false.
Edit:
Code is working now, what i changed:
1* From:
%-- hint 5 - next_to
member(house(LIGHT, _, _, _, _, light), Houses),
member(house(CAT, _, _, cat, _, light), Houses),
To:
%-- hint 5 - next_to
member(house(LIGHT, _, _, _, _, light), Houses),
member(house(CAT, _, _, cat, _, _), Houses),
2* From:
%-- hint 13 - next_to
member(house(HORSE, _, _, horse, _, _), Houses),
next_to(HORSE, GREEN, N),
To:
%-- hint 13 - next_to
member(house(YELLOW, yellow, _, _, _, _), Houses),
member(house(HORSE, _, _, horse, _, _), Houses),
next_to(HORSE, YELLOW, N),
If you are reading this look at @Enigmativity comment about structures in helper predicates aswell.
See Question&Answers more detail:
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