Rubyの練習。一次元セルオートマトン。

elementary-cellular-automaton.rb

class String
  def zfill(width)
    self.rjust(width, '0')
  end
end

class ElementaryCellularAutomaton
  attr_reader :rule, :width, :cells

  def initialize(rule = rand(256), width = 75)
    @rule = rule
    @width = width
  end

  def rule=(rule)
    @rule = rule.to_s(2).zfill(8).reverse.split('').map(&:to_i)
  end

  def width=(width)
    @width = width.to_i
  end

  def cells=(cells)
    @cells = cells.to_a
  end

  def init
    @cells = [].fill(0, 0 ... @width)
    @cells[@cells.size / 2] = 1
  end

  def update
    new_cells = []

    for x in 0 ... @cells.size
      new_cells.push(@rule[
        (@cells[x - 1] << 2) | (@cells[x] << 1) | @cells[(x + 1) % @cells.size]
      ])
    end

    @cells = new_cells
  end

  def to_s
    @cells.map do |cell|
      cell == 1 ? '#' : ' '
    end.join('')
  end
end

if __FILE__ == $0
  eca = ElementaryCellularAutomaton.new(90)
  eca.init

  32.times do
    puts eca.to_s
    eca.update
  end
end