A tic-tac-toe enumerator in Prolog

tris.pro

/**
 * Usage:
 *
 * play(A, "X", "O").  % Gets boards where X wins and O loses
 * play(A, "O", "X").  % Gets boards where O wins and X loses
 * play([[_,_,_], [_,"X",_], [_,_,_]], "X", "O")  % Finds winning boards for X with that starting condition
 * play([[_,_,_], [_,"X",_], [_,_,_]], "O", "X")  % Finds winning boards for O with that starting condition
 * ... 
 */

winning_line([A, B, C], PLAYER) :- 
    A = B,
    A = C,
    A = PLAYER.

winning_row([[A, B, C], [D, E, F], [G, H, I]], PLAYER) :-
    winning_line([A, B, C], PLAYER);
    winning_line([D, E, F], PLAYER);
    winning_line([G, H, I], PLAYER).

winning_col([[A, B, C], [D, E, F], [G, H, I]], PLAYER) :-
    winning_line([A, D, G], PLAYER);
    winning_line([B, E, H], PLAYER);
    winning_line([C, F, I], PLAYER).

winning_dia([[A, _, C], [_, E, _], [G, _, I]], PLAYER) :-
    winning_line([A, E, I], PLAYER);
    winning_line([C, E, G], PLAYER).

winning_board(BOARD, PLAYER) :-
    winning_row(BOARD, PLAYER);
    winning_col(BOARD, PLAYER);
    winning_dia(BOARD, PLAYER).

count_cell(CELL, X, O) :-
    CELL = "X",
    X = 1, O = 0;
    CELL = "O",
    X = 0, O = 1;
    CELL = " ",
    X = 0, O = 0.

count_line([A, B, C], X, O) :-
    count_cell(A, X1, O1),
    count_cell(B, X2, O2),
    count_cell(C, X3, O3),
    X is X1 + X2 + X3,
    O is O1 + O2 + O3.

count_board([A, B, C], X, O) :-
    count_line(A, X1, O1),
    count_line(B, X2, O2),
    count_line(C, X3, O3),
    X is X1 + X2 + X3,
    O is O1 + O2 + O3.

valid_board(BOARD) :-
    count_board(BOARD, X, O),
    O = X; 
    count_board(BOARD, X, O),    
    O = X + 1.

play(BOARD, WIN, LOSE) :-
    valid_board(BOARD),
    winning_board(BOARD, WIN),
    \+ winning_board(BOARD, LOSE).