modulo

/*
 *  call-seq:
 *     big % other         => Numeric
 *     big.modulo(other)   => Numeric
 *
 *  Returns big modulo other. See Numeric.divmod for more
 *  information.
 */

static VALUE
rb_big_modulo(x, y)
    VALUE x, y;
{
    VALUE z;

    switch (TYPE(y)) {
      case T_FIXNUM:
        y = rb_int2big(FIX2LONG(y));
        break;

      case T_BIGNUM:
        break;

      default:
        return rb_num_coerce_bin(x, y);
    }
    bigdivmod(x, y, 0, &z);

    return bignorm(z);
}