On: Write A Function To Determine If A Number Is A Pow...

[nevinera]

Negative numbers cannot be powers of two.

[darwinGod → nevinera]

That's definitely true- but say you want to check for (+/-2)^n, then you would have to deal with negative numbers.

If you go by the Two's complement representation, then for a negative number say (-8), because of sign extention, a check for x&(x-1) would fail.