Prolog domino game

Question

i\'m making a game in prolog, with a given set of domino pieces, it should make a correct domino row using all the pieces in the initial set. we must use an inference system

Answer 1

domino(X) :tasselli(L), member(T,L), componibile(X,L,[T]).
componibile(X,L,X) :length(L,N), length(X,N).
componibile(X,L,A) :member(T,L),
                    \+(member(T,A)),
                    T = t(_,N2),
                    A = [t(N2,_)|_],
                    componibile(X,L,[T|A]).

So if you have:

tasselli([t(3,4),t(5,3),t(4,1),t(1,5)]).

Then the result will be:

?domino(X).

X = [t(4, 1), t(1, 5), t(5, 3), t(3, 4)] ;

X = [t(3, 4), t(4, 1), t(1, 5), t(5, 3)] ;

X = [t(1, 5), t(5, 3), t(3, 4), t(4, 1)] ;

X = [t(5, 3), t(3, 4), t(4, 1), t(1, 5)] ;

false.

Answer 2

Consider something like this:

% L1 is a list of domino pieces (of the form X-Y)
% L2 is L1 in domino order
domino_order(L1, L2) :-
    domino_order(L1, _, L2).

domino_order([], _, []) :- !.
domino_order(In, X, [X-Y | Out]) :-
    select(Piece, In, Remaining),
    swap_or_not(Piece, X-Y),
    domino_order(Remaining, Y, Out).

swap_or_not(X-Y, X-Y).
swap_or_not(X-Y, Y-X).

Usage:

?- domino_order([5-4, 1-2, 4-3, 2-3], Out).
Out = [5-4, 4-3, 3-2, 2-1] ;
Out = [1-2, 2-3, 3-4, 4-5] ;
false.