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.