#!/usr/local/bin/ruby
#!/usr/bin/ruby
class FlipFlop
  def initialize(init=false)
    @p = !init
  end
  def to_b
    @p = !@p
  end
end

fl = FlipFlop.new()
puts fl.to_b
puts fl.to_b
puts fl.to_b
puts fl.to_b
puts fl && true # false になってはくれない