Checking if an Integer is an Exact Binary Power

[Andrei Alexandrescu via Digitalmars-d]

On 4/23/16 10:41 AM, Dmitry Olshansky wrote:
> On 23-Apr-2016 16:04, Nordlöw wrote:
>> Wanted: CT-trait and run-time predicate for checking whether its single
>> integer parameter is an exact power of two.
>>
>> I guess
>>
>> https://dlang.org/phobos/std_math.html#.truncPow2
>>
>> or
>>
>> https://dlang.org/phobos/std_math.html#.nextPow2
>>
>> could be reused, but I bet there's a more efficient way of checking this.
>
> x & (x-1) == 0

Yah, that's the canonical. I forgot why I chose (x & -x) > (x - 1) over 
it. -- Andrei