package Games::AlphaBeta::Position;
use base qw(Games::Sequential::Position);

use strict;
use warnings;

use Carp;

our $VERSION = '0.1.2';

=head1 NAME

Games::AlphaBeta::Position - base Position class for use with Games::AlphaBeta 

=head1 SYNOPSIS

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

    sub apply { ... }
    sub endpos { ... }      # optional
    sub evaluate { ... }
    sub findmoves { ... }

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


=head1 DESCRIPTION

Games::AlphaBeta::Position is a base class for position-classes
that can be used with L<Games::AlphaBeta>. It inherits most of
its methods from L<Games::Sequential::Position>; make sure you
read its documentation.

This class is provided for convenience. You don't need this class
in order to use L<Games::AlphaBeta>. It is, however, also
possible to make use of this class on its own.

=head1 INHERITED METHODS

The following methods are inherited from
L<Games::Sequential::Position>:

=over

=item new 

=item init 

=item copy

=item player 

=back

=head1 VIRTUAL METHODS

Modules inheriting this class must implement the following
methods (in addition to C<apply()> and anything else required by
L<Games::Sequential::Position>): C<evaluate()> &amp;
C<findmoves()>. 

=over 4

=item findmoves()

Return an array of all moves possible for the current player at
the current position. Don't forget to return a null move if the
player is allowed to pass; an empty array returned here denotes
an ending position in the game.

=cut

sub findmoves { 
    croak "Called pure virtual method 'findmoves'\n";
}

=item evaluate()

Return the "fitness" value for the current player at the current
position.

=cut

sub evaluate { 
    croak "Called pure virtual method 'evaluate'\n";
}


=back


=head1 METHODS 

The following methods are provided by this class.

=over 4

=item endpos

True if the position is an ending position, i.e. either a draw or
a win for one of the players.

Note: Not all games need this method, so the default
implementation provided by this modules always returns false. 

=cut

sub endpos { return undef; }

1;  # ensure using this module works
__END__

=back


=head1 SEE ALSO

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


=head1 AUTHOR

Stig Brautaset, E<lt>stig@brautaset.orgE<gt>


=head1 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.

=cut

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