second.rb

class Cell
  def self.random
    number = Random.rand(100)
    if number > 50
      live
    else
      dead
    end
  end

  def self.live
    new(true)
  end

  def self.dead
    new(false)
  end

  def initialize(live)
    @live = live
  end

  def live?
    @live
  end

  def dead?
    !live?
  end

  def evolve(neighbours)
    live_count = neighbours.count(&:live?)
    if live?
      if live_count < 2 || live_count > 3
        Cell.dead
      else
        Cell.live
      end
    else
      if live_count == 3
        Cell.live
      else
        Cell.dead
      end
    end
  end
end

class Grid
  def self.random(width, height)
    new(
      (1..height).map {
        (1..width).map { Cell.random }
      }
    )
  end

  def initialize(rows)
    @rows = rows
    @width = rows.first.length
    @height = rows.length
  end

  def evolve
    Grid.new(
      @rows.map do |row|
        row.map do |cell|
          cell.evolve(neighbours(cell))
        end
      end
    )
  end

  def neighbours(cell)
    x, y = coordinates(cell)

    north = @rows[(y - 1) % @height][(x) % @width]
    northeast = @rows[(y - 1) % @height][(x + 1) % @width]
    east = @rows[(y) % @height][(x + 1) % @width]
    southeast = @rows[(y + 1) % @height][(x + 1) % @width]
    south = @rows[(y + 1) % @height][(x) % @width]
    southwest = @rows[(y + 1) % @height][(x - 1) % @width]
    west = @rows[(y) % @height][(x - 1) % @width]
    northwest = @rows[(y - 1) % @height][(x - 1) % @width]

    [north, northeast, east, southeast, south, southwest, west, northwest]
  end

  def coordinates(cell)
    @width.times do |x|
      @height.times do |y|
        return [x, y] if @rows[y][x] == cell
      end
    end
  end

  def putsit
    puts "-" * @width
    @rows.each do |row|
      row.each do |cell|
        if cell.live?
          print "x"
        else
          print " "
        end
      end
      puts
    end
    puts "-" * @width
  end
end

a = Cell.live
b = Cell.live

grid = Grid.random(40, 35)

while true
  grid = grid.evolve
  grid.putsit
  puts
  sleep (1.0 / 24.0)
end