Domanda

I'm going through some of Lewis Carrols logical quizzes and I have a question with riddle number 60 on that page:

(1) The only animals in this house are cats; 
(2) Every animal is suitable for a pet, that loves to gaze at the moon; 
(3) When I detest an animal, I avoid it; 
(4) No animals are carnivorous, unless they prowl at night; 
(5) No cat fails to kill mice; 
(6) No animals ever take to me, except what are in this house; 
(7) Kangaroos are not suitable for pets; 
(8) None but carnivora kill mice; 
(9) I detest animals that do not take to me; 
(10) Animals, that prowl at night, always love to gaze at the moon. 
Univ. "animals"; a = avoided by me; b = carnivora; c = cats; d = detested by me;
e = in this house; h = kangaroos; k = killing mice; l = loving to gaze at the moon;
m = prowling at night; n = suitable for pets, r = taking to me.

Now I come up with the following Prolog program:

animal(cat).
animal(kangaroo).

prowl_at_night(cat).

carnivore(A) :- prowl_at_night(A).

loves_moongazing(A) :- prowl_at_night(A).

animals_in_house(cat).

suitable_pet(A) :-
    animal(A),
    A \= kangaroo,
    loves_moongazing(A).

can_kill_mice(cat).
can_kill_mice(A) :- carnivore(A).

take_to_me(A) :- animals_in_house(A).

detest(A) :- \+ take_to_me(A).

avoid(A) :- animal(A), detest(A).

Now first I'm not sure what taking to me actually means. Second, if I query Prolog: ?- avoid(A) unifies with A = kangoroo which is the correct answer, but I find it strange that the take_to_me and can_kill_mice predicates are not used to get this answer. Maybe I'm not seeing the obvious.

È stato utile?

Soluzione

To "take to" something means to get attached to it.

avoid(A) is satisfied if A is an animal and you detest it. You detest something that doesn't take to you. You take to something only if it's a house animal. Thus, Kangaroo is the correct answer.

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