Question

Is minus zero (-0) equivalent to zero (0) in C#?

Answer 1

For integers, there is no binary representation that makes a difference between 0 and -0, so they are by definition equal.

For IEEE floating-point numbers, there is a distinction of negative and positive zero. I made some tests (CLR of .NET Framework 2.0, C# 3) and it seems that they are considered equal, which is actually the behavior expected according to the IEEE 754 standard.

Here’s my test code to show that:

    double minusOne = -1.0;
    double positiveZero = 0.0;
    double negativeZero = minusOne*positiveZero;
    Console.WriteLine("{0} == {1} -> {2}", positiveZero, negativeZero, positiveZero == negativeZero);
    Console.WriteLine("Binary representation is equal: {0}", BitConverter.DoubleToInt64Bits(positiveZero) == BitConverter.DoubleToInt64Bits(negativeZero));

Returns:

0 == 0 -> True
Binary representation is equal: False