Search code examples
prologclassificationnegation

Prolog classification

I'm developing a prolog game about finding animal. The user keeps an animal in his/her mind, answer the questions in game and the AI is trying to find the animal.

My problem is about separating the animal classes:

mammal    :- verify(gives_milk), !.
bird      :- verify(has_feathers), !.

I want to separate this two classes from each other. If the animal is mammal, the AI does not ask "has_feathers".

Solution

  • I don't quite follow how you will query whether an animal is a mammal: you will need the argument of the animal. So a predicate would look like:

    mammal(A) :-
    verify(A,gives_milk),
    !.

    evidently with some kind of database like:

    verify(cow,gives_milk).
verify(crow,has_feathers).
% ...

    Next you can use the negation in Prolog \+ to determine that an animal has no feathers:

    mammal(A) :-
    verify(A,gives_milk),
    \+ verify(A,has_feathers),
    !.

    Do not reuse bird and vice versa, because then you create an infinite loop (unless you allow tabulation support).

    More declarative style

    A more declarative style is probably to specify which aspects should hold and which can't hold. Something like:

    verifies(A,Pos,Neg) :-
    verify_pos(A,Pos),
    verify_neg(A,Neg).

verify_pos(_,[]).
verify_pos(A,[H|T]) :-
    verify(A,H),
    verify_pos(A,T).

verify_neg(_,[]).
verify_neg(A,[H|T]) :-
    \+ verify(A,H),
    verify_neg(A,T).

    Now you can for instance state:

    mammal(A) :-
    verifies(A,[gives_milk],[has_feathers,produces_eggs]).

    etc.