NAME
    Games::AlphaBeta - game-tree search with object oriented interface

SYNOPSIS
        package My::GamePos;
        use base qw(Games::AlphaBeta::Position);

        # initialise starting position
        sub _init { ... }

        # Methods required by Games::AlphaBeta
        sub apply { ... }
        sub endpos { ... }          # optional
        sub evaluate { ... }
        sub findmoves { ... }

        # Draw a position in the game (optional)
        sub draw { ... }

        package main;
        my $pos = My::GamePos->new;
        my $game = Games::AlphaBeta->new($pos);

        while ($game->abmove) {
            print draw($game->peek_pos);
        }

DESCRIPTION
    Games::AlphaBeta provides a generic implementation of the AlphaBeta
    game-tree search algorithm (also known as MiniMax search with alpha beta
    pruning). This algorithm can be used to find the best move at a
    particular position in any two-player, zero-sum game with perfect
    information. Examples of such games include Chess, Othello, Connect4,
    Go, Tic-Tac-Toe and many, many other boardgames.

    Users must pass an object representing the initial state of the game as
    the first argument to "new()". This object must provide the following
    methods: "copy()", "apply()", "endpos()", "evaluate()" and
    "findmoves()". This is explained more carefully in
    Games::AlphaBeta::Position which is a base class you can use to
    implement your position object.

INHERITED METHODS
    The following methods are inherited from Games::Sequential:

    new
    debug
    peek_pos
    peek_move
    move
    undo

METHODS
    _init [@list]
        *Internal method.*

        Initialize an AlphaBeta object.

    ply [$value]
        Return current default search depth and, if invoked with an
        argument, set to new value.

    abmove [$ply]
        Perform the best move found after an AlphaBeta game-tree search to
        depth $ply. If $ply is not specified, the default depth is used (see
        "ply()"). The best move found is performed and a reference to the
        resulting position is returned on success, and undef is returned on
        failure.

        Note that this function can take a long time if $ply is high,
        particularly if the game in question has many possible moves at each
        position.

        If "debug()" is set, some basic debugging is printed as the search
        progresses.

    _alphabeta $pos $alpha $beta $ply
        *Internal method.*

BUGS
    The valid range of values "evaluate()" can return is hardcoded to
    -99_999 - +99_999 at the moment. Probably should provide methods to
    get/set these.

TODO
    Implement the missing iterative deepening alphabeta routine.

SEE ALSO
    The author's website, describing this and other projects:
    <http://brautaset.org/projects/>

AUTHOR
    Stig Brautaset, <stig@brautaset.org>

COPYRIGHT AND LICENCE
    Copyright (C) 2004 by Stig Brautaset

    This library is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself, either Perl version 5.8.3 or, at
    your option, any later version of Perl 5 you may have available.

