Exemplo n.º 1
0
        /// <summary>
        /// This function is used for floating-point division.
        /// </summary>
        /// <param name="n2"></param>
        //Given two numbers:
        //  In floating point 1 <= a, b < 2, meaning that both numbers have their top bits set.
        //  To calculate a / b, maintaining precision, we:
        //    1. Double the number of digits available to both numbers.
        //    2. set a = a * 2^d (where d is the number of digits)
        //    3. calculate the quotient a <- q:  2^(d-1) <= q < 2^(d+1)
        //    4. if a >= 2^d, s = 1, else s = 0
        //    6. shift a down by s, and undo the precision extension
        //    7. return 1 - shift (change necessary to exponent)
        public int DivAndShift(BigInt n2)
        {
            if (n2.IsZero()) return -1;
            if (digitArray.Length != n2.digitArray.Length) MakeSafe(ref n2);

            int oldLength = digitArray.Length;

            //Double the number of digits, and shift a into the higher digits.
            Pad();
            n2.Extend();

            //Do the divide (at double precision, ouch!)
            Div(n2);

            //Shift down if 'this' >= 2^d
            int ret = 1;

            if (digitArray[oldLength] != 0)
            {
                RSH(1);
                ret--;
            }

            SetNumDigits(oldLength);
            n2.SetNumDigits(oldLength);

            return ret;
        }