Finding the optimal choice for everybody.

choice.pl

:- use_module(library(clpr)).

alice(apple, 1).
alice(banana, 2).
alice(orange, 3).
alice(kiwi, 4).

bob(apple, 1).
bob(orange, 2).
bob(banana, 3).
bob(kiwi, 4).

claire(orange, 1).
claire(apple, 2).
claire(banana, 3).
claire(kiwi, 4).

daniel(banana, 1).
daniel(apple, 2).
daniel(orange, 3).
daniel(kiwi, 4).

unique([]).
unique([_]).
unique([H|T]) :-
    \+ (memberchk(H, T)),
    unique(T).

choice(A, B, C, D) :-
    alice(A, P1),
    bob(B, P2),
    claire(C, P3),
    daniel(D, P4),
    unique([A, B, C, D]),
    {Penalty = P1 + P2 + P3 + P4},
    print(Penalty),
    minimize(Penalty).