Checking if an Integer is an Exact Binary Power

[Xinok via Digitalmars-d]

On Monday, 25 April 2016 at 15:35:14 UTC, Dominikus Dittes 
Scherkl wrote:
> On Monday, 25 April 2016 at 15:27:02 UTC, Xinok wrote:
>> Brute force.
>>
>> http://dpaste.dzfl.pl/882d7cdc5f74
> Yeah. And your test spares the failed case int.min (0x80000000),
> because in this case x & -x is negative, but of cause x>>>1 is 
> positive, so it returns false despite -(2^^31) is in fact a 
> power of two. So this requires an extra cast to work correct 
> (in fact no big difference in the assembly):
>
> return (Unsigned!T)(x & -x) > (Unsigned!T)(x >>> 1);

How is it wrong? Negative numbers are NOT powers of two (unless 
you have an imaginary/complex exponent), so it's still correct to 
return false for -int.min. Should it not?

http://www.wolframalpha.com/input/?i=solve+2^n+%3D+-%282^31%29+for+n