# File lib/backports/1.9.1/stdlib/prime.rb, line 265
    def each
      return self.dup unless block_given?
      if @ubound
        last_value = nil
        loop do
          prime = succ
          break last_value if prime > @ubound
          last_value = yield prime
        end
      else
        loop do
          yield succ
        end
      end
    end