--- self << bits
--- self >> bits

    եȱ黻ҡbits ӥåȤ()˥եȤޤ

    եȤϡӥå(Ǿ̥ӥå(MSB))ݻޤ

        printf("%#b\n", 0b0101 << 1)
        printf("%#b\n", 0b0101 >> 1)

        => 0b1010
           0b10

        p -1 >> 1

        => -1

