%query: play(i,i,o). %% From: "(Arvind Kumar Bansal)" <arvind@mcs.kent.edu> %% %% Here is a program of tic tac toe which one one my student did for %% a course assignment in Logic Programming. It uses Alpha Beta %% pruning for 3 X 3 board. %% %% -Arvind %% Mathematics and Computer Science %% Kent State University %% Kent, OH 44242 :- entry(play(Game),[ground(Game)]). :- trust(player(Player),[],[ground(Player)]). :- trust(abolish0(Player),[],[ground(Player)]). play(Game) :- initialize(Game, Position, Player), display_game(Position), play(Position, Player, Result). play(Position, Player, Result) :- game_over(Position, Player, Result), !, write(Result), abolish0(player). play(Position, Player, Result) :- choose(Position, Player, Move), move(Move, Player, Position, Position1), display_game(Position1), next_player(Player, Player1), !, play(Position1, Player1, Result). choose(Position, computer, Move) :- write('Computer is thinking...'), nl, alpha_beta(computer, Position, -1, 1, Move, Value). choose(Position, Player, Move) :- write(Player), write(', enter move (followed by a period and return) --> '), read(Move1), legal(Position, Player, Move1, Move). alpha_beta(Player, Position, Alpha, Beta, Move, Value) :- Player == computer, game_win_o(Position), Value is 1. alpha_beta(Player, Position, Alpha, Beta, Move, Value) :- player(Player), game_win_x(Position), Value is 1. alpha_beta(Player, Position, Alpha, Beta, Move, Value) :- game_tie(Position), Value is 0. alpha_beta(Player, Position, Alpha, Beta, Move, Value) :- Player == computer, game_win_x(Position), Value is -1. alpha_beta(Player, Position, Alpha, Beta, Move, Value) :- player(Player), game_win_o(Position), Value is -1. alpha_beta(Player, Position, Alpha, Beta, Move, Value) :- setof(Move1, move(Position, Move1), Moves), Alpha1 is -Beta, Beta1 is -Alpha, evaluate(Player, Moves, Position, Alpha1, Beta1, nil, (Move, Value)). evaluate(Player, [Move | Moves], Position, Alpha, Beta, Move1, Best):- move(Move, Player, Position, Position1), next_player(Player, Player1), alpha_beta(Player1, Position1, Alpha, Beta, MoveX, Value), Value1 is -Value, cutoff(Player, Move, Value1, Alpha, Beta, Moves, Position, Move1, Best), !. evaluate(Player, [], Position, Alpha, Beta, Move, (Move, Alpha)). cutoff(Player, Move, Value, Alpha, Beta, Moves, Position, Move1, (Move,Value)):- Value >= Beta, !. cutoff(Player, Move, Value, Alpha, Beta, Moves, Position, Move1, Best) :- Alpha < Value, Value < Beta, !, evaluate(Player, Moves, Position, Value, Beta, Move, Best). cutoff(Player, Move, Value, Alpha, Beta, Moves, Position, Move1, Best) :- Value =< Alpha, !, evaluate(Player, Moves, Position, Alpha, Beta, Move1, Best). initialize(tictactoe, ((' ',' ',' '), (' ',' ',' '), (' ',' ',' ')), Player) :- write('Enter player`s name (followed by a period and return) --> '), read(Player), write(Player), write(', you will go first and use the symbol "x".'), nl, assert(player(Player)). display_game(((R1C1, R1C2, R1C3), (R2C1, R2C2, R2C3), (R3C1, R3C2, R3C3))) :- nl, write(' '), write(R1C1), write(' '), write('|'), write(' '), write(R1C2), write(' '), write('|'), write(' '), write(R1C3), write(' '), tab(3), write('u-l = upper left, u-c = upper center, u-r = upper right'), nl, write(' --+---+-- '), nl,
content may be truncated. 'popout' for larger text window.
