Microsoft.Scripting.Math.BigInteger.operator C# (CSharp) Method

    public static BigInteger operator +(BigInteger x, BigInteger y) {
      if (object.ReferenceEquals(x, null)) {
        throw new ArgumentNullException("x");
      }
      if (object.ReferenceEquals(y, null)) {
        throw new ArgumentNullException("y");
      }

      if (x.sign == y.sign) {
        return new BigInteger(x.sign, add0(x.data, x.Length, y.data, y.Length));
      } else {
        return x - new BigInteger(-y.sign, y.data);  //??? performance issue
      }
    }