# File lib/domain_name/punycode.rb, line 78
    def encode_digit(d, flag)
      (d + 22 + (d < 26 ? 75 : 0) - (flag ? (1 << 5) : 0)).chr
      #  0..25 map to ASCII a..z or A..Z
      # 26..35 map to ASCII 0..9
    end