# File lib_wpm/wpm.rb, line 692
    def check_number(string)
      if (string !~ /^(\+|\-)?\d+$/) then
        raise "not a number: #{string.inspect}"
      end
      if (iterator?) then
        unless (yield(string.to_i)) then
          raise "out of range: #{string.inspect}"
        end
      end
      nil
    end