System.Xml.Xsl.XPathConvert.NextAfter C# (CSharp) Method

        public static double NextAfter(double x, double y) {
            long bits;

            if (Double.IsNaN(x)) {
                return x;
            }
            if (Double.IsNaN(y)) {
                return y;
            }
            if (x == y) {
                return y;
            }
            if (x == 0) {
                bits = BitConverter.DoubleToInt64Bits(y) & 1L<<63;
                return BitConverter.Int64BitsToDouble(bits | 1);
            }

            // At this point x!=y, and x!=0. x can be treated as a 64bit
            // integer in sign/magnitude representation. To get the next
            // representable neighbor we add or subtract one from this
            // integer.

            bits = BitConverter.DoubleToInt64Bits(x);
            if (0 < x && x < y || 0 > x && x > y) {
                bits++;
            } else {
                bits--;
            }
            return BitConverter.Int64BitsToDouble(bits);
        }