succ

# File lib/prime.rb, line 335
    def succ
      loop do
        if (@step)
          @prime += @step
          @step = 6 - @step
        else
          case @prime
          when 1; @prime = 2
          when 2; @prime = 3
          when 3; @prime = 5; @step = 2
          end
        end
        return @prime
      end
    end