divmod

static VALUE
fix_divmod(VALUE x, VALUE y)
{
    if (FIXNUM_P(y)) {
        long div, mod;

        fixdivmod(FIX2LONG(x), FIX2LONG(y), &div, &mod);

        return rb_assoc_new(LONG2NUM(div), LONG2NUM(mod));
    }
    switch (TYPE(y)) {
      case T_BIGNUM:
        x = rb_int2big(FIX2LONG(x));
        return rb_big_divmod(x, y);
      case T_FLOAT:
        {
            double div, mod;
            volatile VALUE a, b;

            flodivmod((double)FIX2LONG(x), RFLOAT_VALUE(y), &div, &mod);
            a = dbl2ival(div);
            b = DBL2NUM(mod);
            return rb_assoc_new(a, b);
        }
      default:
        return rb_num_coerce_bin(x, y, rb_intern("divmod"));
    }
}