game_of_life.rb

class GameOfLife
  
  DEAD  = 0
  ALIVE = 1
  
  attr_accessor :state
  
  def initialize(size=20)
    @size = size
    @state = Array.new(@size){ Array.new(@size){ rand 2 } }
  end
  
  def evolve
    new_state = Array.new(@size){ Array.new(@size) }
    @state.each_with_index do |row, x|
      row.each_with_index do |cell,y|
        new_state[x][y] = case (count_live_neighbours_near(x,y))
        when 2
          alive?(x,y) ? ALIVE : DEAD
        when 3
          ALIVE
        else 
          DEAD
        end
      end
    end
    @state = new_state
  end
  
  def count_live_neighbours_near(x,y)
    neighbours_near(x,y).
    select{ |a,b| alive?(a,b) }.
    length
  end
  
  def alive?(x,y)
    @state[x%@size][y%@size] == ALIVE
  end
  
  def neighbours_near(x,y)
      [
        [x-1,y-1],[x-1,y],[x-1,y+1],
        [ x ,y-1],        [x  ,y+1],
        [x+1,y-1],[x+1,y],[x+1,y+1]
      ]
  end
  
end

gistfile5.txt

helper.rb

require 'rubygems'
require 'test/unit'

$LOAD_PATH.unshift(File.dirname(__FILE__))
$LOAD_PATH.unshift(File.join(File.dirname(__FILE__), '..', 'lib'))
require 'game_of_life'

class Test::Unit::TestCase
end

life_web.rb

require 'rubygems'
require 'sinatra'
require 'haml'
require File.join(File.dirname(__FILE__), 'game_of_life')

get '/game/new' do
  @game = GameOfLife.new(28)
  haml :index
end

get '/game/evolve' do
  @game = GameOfLife.new(28)
  @game.state = Array.new(28){ Array.new(28){ 0 } }
  params[:state].each_pair do |x,row|
    row.each_pair do |y,value|
      @game.state[x.to_i][y.to_i] = value.to_i
    end
  end
  @game.evolve
  haml :index
end

__END__

@@ layout
%html
%h1 Game of Life
= yield

@@ index
%form.game{:action => "/game/evolve"}
  - @game.state.each_with_index do |row, x|
    .row
      - row.each_with_index do |cell,y|
        %input{:type=>"radio", :name => "state[#{x}][#{y}]", :value => 1, :checked => (cell==1)}
  %input{:type => "submit", :value => "evolve"}
%script(type="text/javascript"
          src="http://code.jquery.com/jquery-latest.js")
:javascript
  var refreshId = setInterval(function()
  {
       $('form.game').submit();
  }, 1000);

test_game_of_life.rb

require 'helper'

class TestGameOfLife < Test::Unit::TestCase
  def setup
    @game = GameOfLife.new(3)
  end

  def test_should_kill_with_no_neighbours
    @game.state = [[1,0,0],[0,0,0],[0,0,0]]
    after = @game.evolve
    assert_equal after[0][0], 0
  end

  def test_should_kill_with_just_one_neighbour
    @game.state = [[0,0,0],[1,0,0],[1,0,0]]
    after = @game.evolve
    assert_equal after[1][0], 0
    assert_equal after[2][0], 0
  end
  
  def test_should_survive_with_two_neighbours
    @game.state = [[0,0,0],[1,1,0],[1,0,0]]
    after = @game.evolve
    assert_equal after[1][1], 1
  end
  
  def test_should_not_give_birth_if_2_neighbours
    @game.state = [[0,0,0],[1,0,1],[0,0,0]]
    after = @game.evolve
    assert_equal after[1][1], 0
  end
  
  def test_should_not_give_birth_if_4_neighbours
    @game.state = [[0,1,0],[1,0,1],[0,1,0]]
    after = @game.evolve
    assert_equal after[1][1], 0
  end
  
  def test_should_survive_with_three_neighbours
    @game.state = [[0,0,0],[1,1,0],[1,1,0]]
    after = @game.evolve
    assert_equal after[1][1], 1
  end

  def test_should_kill_with_more_than_3_neighbours
    @game.state = [[1,1,1],[1,1,1],[1,1,1]]
    after = @game.evolve
    assert_equal after, [[0,0,0],[0,0,0],[0,0,0]]
  end

  def test_should_give_birth_if_3_neighbours
    @game.state = [[1,0,0],
                   [1,1,0],
                   [0,0,0]]
    assert_equal 2,@game.count_live_neighbours_near(1,0)
    after = @game.evolve
    assert_equal after, [[1,1,1],[1,1,1],[1,1,1]]
  end
  
  def test_count_live_neighbours
    @game.state = [[0,0,0],
                   [0,1,0],
                   [0,0,0]]
    assert_equal 1,@game.count_live_neighbours_near(1,0)
    assert_equal 0,@game.count_live_neighbours_near(1,1)
    @game.state = [[1,0,0],
                   [1,1,0],
                   [0,0,0]]
    assert_equal 3,@game.count_live_neighbours_near(0,1)
    assert_equal 2,@game.count_live_neighbours_near(1,0)
  end
end