--- hex

    ʸ 16 ʿɽȲᤷơѴޤ

        p "10".hex    # => 16
        p "ff".hex    # => 255
        p "0x10".hex  # => 16
        p "-0x10".hex # => -16

    Ƭ "0x", "0X" ̵뤵ޤ[_0-9a-fA-F] ʳ
    ʸФޤǤѴоݤȤޤѴоݤʸǤ 
    0 ֤ޤ

        p "xyz".hex   # => 0
        p "10z".hex   # => 16
        p "1_0".hex   # => 16

    oct, to_i, to_f, 
    Integer, Float 
    ⻲ȤƤ

    դˡͤʸѴˤ 
    sprintf,
    %,
    Integer#to_s [Integer/to_s]
    Ѥޤ

