Игра - Prolog

% pn_step(State, Step, Player, Move, X, Y).
:- dynamic(pn_step/6).
 
pn_init(15, 17).
 
pn_act(x, -2).
pn_act(x, 5).
pn_act(y, -3).
pn_act(y, 2).
 
pn_limit(x, 9, 20).
pn_limit(y, 9, 20).
 
pn_win(Z, Z).
 
pn_loss(14, 13).
 
pn_go(Method) :-
    retractall( pn_step(_, _, _, _, _, _) ),
    Step = 0,
    Player = n,
    pn_init(X, Y),
    Move = 0,
    State = start,
    asserta( pn_step(State, Step, Player, Move, X, Y) ),
    format('~w ~w ~w ~w ~w ~w~n', [State, Step, Player, Move, X, Y]),
    between(0, 100, N), N < 100,
    pn_play(Method),
    ( pn_step(win, _, _, _, _, _)
    ; pn_step(loss, _, _, _, _, _)
    ),
    !.
 
pn_play(Method) :-
    once( pn_step(_, Step, Player, _, X, Y) ),
    ( Player = x
     ->
      Player1 = y
    ; Player1 = x
    ),
    pn_play(Method, Player1, X, Y, X1, Y1, Move),
    Step1 is Step + 1,
    ( pn_win(X1, Y1),
      State1 = win
    ; pn_loss(X1, Y1),
      State1 = loss
    ; State1 = step
    ),
    asserta( pn_step(State1, Step1, Player1, Move, X1, Y1) ),
    format('~w ~w ~w ~w ~w ~w~n', [State1, Step1, Player1, Move, X1, Y1]),
    !.
  
pn_play(1, x, X, Y, X1, Y, Move) :-
    pn_move(1, x, X, X1, Move).
pn_play(1, y, X, Y, X, Y1, Move) :-
    pn_move(1, y, Y, Y1, Move).
 
pn_play(2, x, X, Y, X1, Y, Move) :-
    setof( Delta-X0-Move0,
           ( pn_move(1, x, X, X0, Move0),
             Delta is abs(abs(X0) - abs(Y))
           ),
           Moves ),
    select(_-X1-Move, Moves, _),
    \+ pn_loss(X1, Y),
    \+ ( pn_move(1, y, Y, Y1, _), pn_win(X1, Y1) ).
pn_play(2, y, X, Y, X, Y1, Move) :-
    setof( Delta-Y0-Move0,
           ( pn_move(1, y, Y, Y0, Move0),
             Delta is abs(abs(X) - abs(Y0))
           ),
           Moves ),
    select(_-Y1-Move, Moves, _),
    \+ pn_loss(X, Y1),
    \+ ( pn_move(1, x, X, X1, _), pn_win(X1, Y1) ).
pn_play(2, Player, X, Y, X1, Y1, Move) :-
    pn_play(1, Player, X, Y, X1, Y1, Move).
 
pn_move(1, Player, Z, Z1, Move) :-
    pn_act(Player, Move),
    Z1 is Z + Move,
    pn_limit(Player, Low, High),
    Low < Z1, Z1 < High.
 
/** <examples>
?- pn_go(1).
?- pn_go(2).
*/