Komachi calculation

komachi.pl

% komachi

digit(X) :- member(X, [0,1,2,3,4,5,6,7,8,9]).

is_composed_of(N, X, Y) :-
  digit(X),
  digit(Y),
  (Z is X+Y;
    Z is X-Y;
    Z is Y-X;
    Z is X*Y;
    (Y =\= 0, Z is X/Y, Mod is X mod Y, Mod == 0)),
  Z == N.

komachi(A, B, C, D, Sum) :-
  is_composed_of(Sum, X, Y),
  is_composed_of(X, A, B),
  is_composed_of(Y, C, D).

enum :-
  (komachi(A, B, C, D, 10);
    komachi(A, C, B, D, 10);
    komachi(A, D, B, C, 10)),
  print([A,B,C,D]), nl, fail.