% Author:RL
% Date: 04/10/2016

colours([red,blue,orange, plaid]).
names([fred,joe, bob, tom]).
positions([1,2,3,4]).

% golfer(Name,Position,Colour)


go :- positions(Ps), colours(Cs),
      pick(P1, Ps, Ps1), pick(C1, Cs, Cs1), G1 = golfer(fred, P1, C1),
      pick(2, Ps1, Ps2), pick(C2, Cs1, Cs2), G2 = golfer(joe, 2, C2),
      pick(P3, Ps2, Ps3), pick(plaid, Cs2, Cs3), G3 = golfer(bob, P3, plaid),
      pick(P4, Ps3, _), pick(C4, Cs3, _), G4 = golfer(tom, P4, C4),

      asserta(G1), asserta(G2), asserta(G3), asserta(G4),
      
      ( golfer(fred, X, _), Y is X+1, golfer(_, Y, blue),
        golfer(tom, Pos, Col), Pos =\= 1, Pos =\= 4, Col \== orange
      ; clear(G1,G2,G3,G4), fail),
      write(G1), nl, write(G2), nl, write(G3), nl, write(G4), nl,
      clear(G1,G2,G3,G4).

clear(G1,G2,G3,G4) :-retract(G1), retract(G2), retract(G3), retract(G4).

pick(X, [X|T], T).
pick(X, [H|T], [H|T2]) :- pick(X, T, T2).