Does float have a negative zero? (-0f)

Question

IEEE floating point numbers have a bit assigned to indicate the sign, which means you can technically have different binary representations of zero (+0 and -0). Is there an

Answer 1

There are a couple of simple arithmetic operations that result in a negative zero answer (at least on the i386/x64/ARMv7/ARMv8 systems I tested it on) :

• -1 * 0
• 0 / -1

These caught me by surprise when I was writing an optimiser to simplify arithmetic expressions. Optimising "a = b * 0" to "a = 0" will result in the wrong answer (+0) if b happens to be negative (correct answer is -0).