view release on metacpan or  search on metacpan

Life.pm  view on Meta::CPAN

		    $self->_determine_life_status( $i, $j );
	    }
	}
	$self->{ grid } = $new_grid;
    }
}

sub _determine_life_status {
    my ( $self, $x , $y ) = @_;
    my $n = 0;
    for my $i ( $x-1, $x, $x+1 ) {
	for my $j ( $y-1, $y, $y+1 ) {
	    $n++ if ( $i >= 0 && $i < $self->{ size_x } &&
		      $j >= 0 && $j < $self->{ size_y } ) && 
			  ( $self->{ grid }->[ $i ]->[ $j ] );
	}
    }
    # here's the deterministic part; force return of 0 or 1.
    $n-- if $self->{ grid }->[ $x ]->[ $y ];
    return ( 0 != grep { $_ == $n } @{ $self->{ 
	$self->{ grid }->[ $x ]->[ $y ] 
	    ? 'keep_criteria' : 'breed_criteria' } } );
}

42;

__END__

=pod 

=head1 NAME
    
Game::Life - Plays Conway's Game of Life

=head1 SYNOPSIS

	use Game::Life;
	my $game = new Game::Life( 20 );
	my $starting = [
			 [ 1, 1, 1 ],
			 [ 1, 0, 0 ],
			 [ 0, 1, 0 ]
		       ];

	$game->place_points( 10, 10, $starting );
	for (1..20) {
	    my $grid = $game->get_grid();
	    foreach ( @$grid ) {
		print map { $_ ? 'X' : '.' } @$_;
		print "\n";
	    }
	    print "\n\n";
	    $game->process();
	}

=head1 DESCRIPTION

Conway's Game of Life is a basic example of finding 'living' patterns
in rather basic rulesets (see B<NOTES>).  The Game of Life takes
place on a 2-D rectangular grid, with each grid point being either
alive or dead.  If a living grid point has 2 or 3 neighbors within the
surrounding 8 points, the point will remain alive in the next
generation; any fewer or more will kill it.  A dead grid point will
become alive if there are exactly 3 living neighbors to it.  With
these simple rules, fascinating structures such as gliders that move
across the grid, glider guns that generate these gliders, XOR gates,
and others have been found.

This module simply provides a way to simulate the Game of Life in Perl.

In terms of coordinate systems as used in C<place_points>, C<toggle_point>
and other functions, the first coodinate is the vertical direction, 0
being the top of the board, and the second is the horizontal direaction,
0 being the left side of the board.  Thus, toggling the point of (3,2) 
will switch the state of the point in the 4th row and 3rd column.

The edges of the board are currently set as "flat"; cells on the edge
do not have any neighbors, and thus will 'fall' off the board.  Future
versions may allow for 'warp' edges (if a cell moves off the left side it 
reappears on the right side).

=over

=item C<new>

Creates a new Life game board; if passed a scalar, the game board will
be a square of that size, if passed an array reference, the game board
will be created as a rectangle with the width and height set to the
first and second values in the array reference respectively, otherwise, 
the board will be created using the default size of 100x100 units.  
Two optional array references may be passed to set the breeding and 
living rules for the Life game, respectively.  The arrays should be 
made of the values for the number of nearest neighbors that should 
trigger the associated event.  By default, Conway's game of life 
uses [ 3 ] and [ 2,3 ] for these arrays, respectively, but you can play 
around with these to get other types of automata.

=item C<set_rules>

Takes two array references and uses them to set the rules of the Life game
as described in C<new> above, namely for breeding and living rules
in that order.

=item C<get_breeding_rules>, C<get_living_rules>

Returns arrays that are associated with the breeding or living rules
above.

=item C<place_points>

Takes two scalars (indicating the position on the grid) and a
reference to an array of arrays; this array is placed into the Life
grid at the specified position, overwriting any data already there.
Within the array of arrays, any non-zero values will be considered as
a living square.

=item C<place_text_points>

Takes two scalars (indicated the position on the grid), a character,
and an array of strings; as with C<place_points>, this array will
be placed into the grid at the specified position.  The character indicates
what cells are to be considered as alive; any other character in the 
string will be considered dead.  Thus, the example given in the B<SYNOPSIS>
can be writen optionally as

	my @starting = qw( XXX
                           X..
                           .X. );

	$game->place_text_points( 10, 10, 'X', @starting );

Note that a implicit method of serialization can be used in conjunction with
C<get_text_grid>.

=item C<toggle_point>, C<set_point>, C<unset_point>

Take two scalars that indiciate a specific grid position.  These
functions toggle, sets, or unsets the life status of the grid point
passed, respectively.

=item C<process>

If passed a number, runs the Life simulation that many times, else
runs the simulation once.

=item C<get_grid>

Returns a B<copy> of the Life grid as a reference to an array of
arrays.

=item C<get_text_grid>

Returns an array of strings that represent the game board.  Two optional
parameters may be passed as symbols to represent the living and dead states
on the board, in that order.  If these are not supplied, they will be
represented by 'X' and '.', respectively.  It's very easy to use this via:

	print "$_\n" foreach ( $game->get_text_grid( ) );

to follow the progress of the Life simulation, and should be faster than
rolling your own based on get_grid.  

=back

=head1 NOTES

Conway here is not Damien Conway of Perl fame, but John Horton Conway of
mathematics and computer science fame.  The 'game' was original designed
in the late 60s - early 70s, and became popular due to the interest that
Martin Gardner (puzzle editor for I<Scientific American>) had for it.

=head1 HISTORY

    Revision 0.06  2013/05/16 08:55:32  ltp

    Improved test coverage.

    Revision 0.05  2013/05/15 21:18:26  ltp

    Updated constructor to allow arbitrary sized game board.

    Revision 0.04  2001/07/04 02:49:29  mneylon