Work with character sets:

    Chars.hexadecimal
    # => #<Chars::CharSet: {"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "A", "B", "C", "D", "E", "F", "a", "b", "c", "d", "e", "f"}>

    (Chars.printable - Chars.alpha_numeric).bytes.sort
    # => [32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 58, 59, 60, 61, 62, 63, 64, 91, 92, 93, 94, 95, 96, 123, 124, 125, 126]