How can I test for negative zero?

Question

Initially I thought Math.Sign would be the proper way to go but after running a test it seems that it treats -0.0 and +0.0 the same.

Answer 1

Here's a grotty hack way of doing it:

private static readonly long NegativeZeroBits =     BitConverter.DoubleToInt64Bits(-0.0);  public static bool IsNegativeZero(double x) {     return BitConverter.DoubleToInt64Bits(x) == NegativeZeroBits; } 

Basically that's testing for the exact bit pattern of -0.0, but without having to hardcode it.

Answer 2

After a bit of searching I finally made it to Section 7.7.2 of the C# specification and came up with this solution.

private static bool IsNegativeZero(double x) {     return x == 0.0 && double.IsNegativeInfinity(1.0 / x); }