Chess::Game - a class to record and validate the moves of a game of chess
use Chess::Game;
$game = Chess::Game->new();
$clone = $game->clone();
$move = $game->make_move("e2", "e4");
$move_c = $clone->make_move("e2", "e4");
$true = ($move->get_piece() ne $move_c->get_piece());
$move = $game->delete_move();
...
while (!defined($result = $game->result())) {
# get a move
$move = $game->make_move($sq1, $sq2);
if (!defined($move)) {
print $game->get_message();
}
}
if ($result == 1) {
print "White wins!\n";
}
elsif ($result == 0) {
print "Draw!\n"
}
else {
print "Black wins!\n";
}
The Chess module provides a framework for writing chess programs with Perl. This class forms part of that framework, providing move validation for all moves recorded using the Chess::Game class. The Game contains a the Chess::Board manpage, 32 the Chess::Piece manpages and a the Chess::Game::MoveList manpage that contains a series of the Chess::Game::MoveListEntry manpages that record the exact state of the game as it progresses. Moves can be taken back one-at-a-time to allow for simple movelist manipulation.
new()
Takes two optional parameters containing optional names for the players. If none are provided, the player names 'white' and 'black' are used. Creates a new the Chess::Board manpage and places 16 the Chess::Pieces manpage per player and initializes an empty the Chess::Game::MoveList manpage.
There are no class methods for this class.
clone()
Takes no parameters. Returns a new blessed Chess::Game reference in an identical state to the calling object, but which can be manipulated entirely separately.
is_move_legal()
Takes two parameters containing the name of the square to move from and the name of the square to move to. They should be validated with square_is_valid() in the Chess::Board manpage prior to calling. Returns true if the provided move is legal within the context of the current game.
make_move()
Takes two parameters containing the name of the square to move from and the name of the square to move to. They should be validated with square_is_valid() in the Chess::Board manpage before calling. Optionally takes a third parameter, which can be set to zero to indicate that no legality checking should be done. In this case, flags indicating 'en passant' pawn captures or castling will not be set! Only by entirely validating the move do these flags have any meaning. The default is to validate every move. Returns a the Chess::Game::MoveListEntry manpage representing the move just made.
get_message()
Takes no parameters. Returns the message containing the reason make_move() or is_move_legal() returned false, such as "Can't castle out of check".
delete_move()
Takes no parameters. Returns a the Chess::Game::MoveListEntry manpage representing the last move made, and sets the state of the game to what it was prior to the returned move being made.
player_in_check()
Takes a single parameter containing the name of the player to consider. Returns true if the named player is in check.
player_checkmated()
Takes a single parameter containing the name of the player to consider. Returns true if the named player has been checkmated.
player_stalemated()
Takes a single parameter containing the name of the player to consider. Returns true if the named player has been stalemated.
result()
Takes no parameters. Returns undef as long as the game is in progress. When
a conclusion has been reached, returns 1 if the first player checkmated the
second player, 0 if either player has been stalemated, or -1 if the second
player checkmated the first player. Is not currently able to determine if the
game was drawn by a three-fold repetition of positions.
do_promotion()
Takes one parameters. If the last move was a promotion (as determined by a call to is_promotion() in the Chess::Game::MoveListEntry manpage, then calling this function will change the newly promoted pawn to the piece specified by the provided parameter. Valid values are (case-insensitive) "bishop", "knight", "queen" and "rook".
The program contains a reference to a Chess::Game not obtained through new() or clone(). Ensure the program only uses these methods to create Chess::Game references, and the the reference refers to a defined value.
The program made a call to make_move() or is_move_legal() with invalid squares.
Ensure that all variables containing squares are validated with
square_is_valid() in the Chess::Board manpage.
The framework is not currently able to determine when a game has been drawn by three-fold repetition of position. Please report any other bugs to the author.
Brian Richardson <bjr@cpan.org>
Copyright (c) 2002, 2005 Brian Richardson. All rights reserved. This module is Free Software. It may be modified and redistributed under the same terms as Perl itself.