public BigInteger divide(BigInteger val)
private static void divide(long x, long y, BigInteger quotient, BigInteger remainder, int rounding_mode)
  public BigInteger divide(BigInteger val)  {    if (val.isZero())      throw new ArithmeticException("divisor is zero");    BigInteger quot = new BigInteger();    divide(this, val, quot, null, TRUNCATE);    return quot.canonicalize();  }