NAME

Game::Life - Plays Conway's Game of Life

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();
}

DESCRIPTION

Conway's Game of Life is a basic example of finding 'living' patterns in rather basic rulesets (see 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 place_points, 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).

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.

set_rules

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

get_breeding_rules, get_living_rules

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

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.

place_text_points

Takes two scalars (indicated the position on the grid), a character, and an array of strings; as with 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 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 get_text_grid.

toggle_point, set_point, 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.

process

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

get_grid

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

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.

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 Scientific American) had for it.

HISTORY

Revision 0.05  2013/05/17 21:18:26  ltp

Updated constructor to allow arbitrary sized game board.

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

Fixed distribution problem

Revision 0.03  2001/07/04 02:27:55  mneylon

Updated README for distribution

Revision 0.02  2001/07/04 02:23:13  mneylon

Added test cases
Added set_text_points, get_text_grid
Added set_rules, get_breeding_rules, get_living_rules, and set default
      values for these as Conway's rules
Modifications from code as posted on Perlmonks.org

AUTHOR

This package was written by Michael K. Neylon

COPYRIGHT

Copyright 2001 by Michael K. Neylon

LICENSE

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.