digit (Randexp::Reducer)

    # 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