Programming without conditional statements.

polymorphism.rb

class DeadCell

  def to_s
    ' '
  end

end

class AliveCell

  def to_s
    '*'
  end

end

def print_world(*cells)
  cells.each do |cell|
    print cell
  end
end

print_world(AliveCell.new, DeadCell.new)

strategy.rb

serializers = {
  :alive => 'x',
  :dead  => ' '
}

class Cell

  def initialize(state)
    @state = state
  end

  def state?
    @state
  end

end

def print_world(serializers, *cells)
  cells.each do |cell| 
    print serializers.fetch(cell.state)
  end
end

print_world(serializers, Cell.new(:alive), Cell.new(:dead))

traditional.rb

class Cell

  def initialize(alive)
    @alive = alive
  end

  def alive?
    @alive
  end

end

def print_world(*cells)
  cells.each do |cell|
    if cell.alive? 
      print 'x'
    else
      print ' '
    end
  end
end

print_world(Cell.new(true), Cell.new(false))