Behaviour of negative zero (-0.0) in comparison with positive zero (+0.0)

Question

In my code,

float f = -0.0; // Negative 

and compared with negative zero

f == -0.0f

res

Answer 1

That's because the signed negative zero must compare true with zero: i.e. -0.0 == 0.0, -0f == 0f, and -0l == 0l.

It's a requirement of any floating point scheme supported by a C++ compiler.

(Note that most platforms these days use IEEE754 floating point, and this behaviour is explicitly documented in that specification.)