quattro.pl

% 0 - Not found | 1 - GG | 2 - GS
contains(_ ,_, [],    _, 0).
contains(H, P, [H|_], P, 1).
contains(H, P, [H|_], Q, 2) :- P \== Q.
contains(H, P, [M|T], Q, O) :- H \== M, QQ is Q + 1, contains(H, P, T, QQ, O).

% Short version of contains/5
contains(H, P, L, O) :- contains(H, P, L, 1, O).

% Increase GG or GS depending on result
increase(0, GG, GS, GG,  GS).
increase(1, GG, GS, GG + 1, GS).
increase(2, GG, GS, GG, GS + 1).

% Check two numbers and returns number of full/partial matches
check([],      _, _, GG, GS, GG,  GS).
check([HI|TI], I, O, GG, GS, GGG, GSS) :-
    contains(HI, I, O, RES),
    IX is I + 1,
    increase(RES, GGG, GSS, GG2, GS2),
    check(TI, IX, O, GG, GS, GG2, GS2).

% Short version of check/4
check(I, O, GG, GS) :- check(I, 1, O, GG, GS, 0, 0).

guess(I, O) :-
    check(I, O, GG, GS),
    format("~D gg ~D gs~n",[GG,GS]).

main :-
    guess("1423","1243"),
    guess("5143","5143"),
    guess("9876","1234").