public BigInteger AndNot(
     BigInteger val)
 {
     return And(val.Not());
 }
        public BigInteger And(
            BigInteger value)
        {
            if (this.sign == 0 || value.sign == 0)
            {
                return Zero;
            }

            int[] aMag = this.sign > 0
                ? this.magnitude
                : Add(One).magnitude;

            int[] bMag = value.sign > 0
                ? value.magnitude
                : value.Add(One).magnitude;

            bool resultNeg = sign < 0 && value.sign < 0;
            int resultLength = System.Math.Max(aMag.Length, bMag.Length);
            int[] resultMag = new int[resultLength];

            int aStart = resultMag.Length - aMag.Length;
            int bStart = resultMag.Length - bMag.Length;

            for (int i = 0; i < resultMag.Length; ++i)
            {
                int aWord = i >= aStart ? aMag[i - aStart] : 0;
                int bWord = i >= bStart ? bMag[i - bStart] : 0;

                if (this.sign < 0)
                {
                    aWord = ~aWord;
                }

                if (value.sign < 0)
                {
                    bWord = ~bWord;
                }

                resultMag[i] = aWord & bWord;

                if (resultNeg)
                {
                    resultMag[i] = ~resultMag[i];
                }
            }

            BigInteger result = new BigInteger(1, resultMag, true);

            // TODO Optimise this case
            if (resultNeg)
            {
                result = result.Not();
            }

            return result;
        }