# File lib/randexp/reducer.rb, line 79
    def self.digit(quantity)
      case quantity
      when '?''?'       then ['', Randgen.digit].pick
      when :+, '+?''+?'  then raise "Sorry, \"\\d+\" is too vague, try setting a range: \"\\d{1, 5}\""
      when :*, '*?''*?'  then raise "Sorry, \"\\d*\" is too vague, try setting a range: \"\\d{0, 5}\""
      when Range      then quantity.pick.of { Randgen.digit } * ''
      when Integer    then quantity.of { Randgen.digit } * ''
      when nil        then Randgen.digit
      end
    end