--- divmod(other)

    self  other ǳä (q) ; (m) 
    [q, m] Ȥ 2 Ǥˤ֤ޤ

    ǡx  y ǳä q ; m Ȥ
    Τϡ줾

       x = y * q + m    |m| < |y|

    ߤ ((**)) q   m ΤȤǤ

     divmod Ǥϡξ˲äơ; 
    other Ʊ(ޤϥ)ˤޤĤޤ
    * other > 0 ΤȤ 0 <= m < other
    * other < 0 ΤȤ other < m <= 0
    Ȥʤޤ

    Υ᥽åɤϡ᥽å /  % ˤäƤޤ

