Checking if an Integer is an Exact Binary Power

[Temtaime via Digitalmars-d]

On Sunday, 24 April 2016 at 21:45:32 UTC, Walter Bright wrote:
> On 4/24/2016 8:33 AM, Andrei Alexandrescu wrote:
>> On 04/24/2016 02:57 AM, deadalnix wrote:
>>> On Saturday, 23 April 2016 at 15:29:08 UTC, Andrei 
>>> Alexandrescu wrote:
>>>> Yah, that's the canonical. I forgot why I chose (x & -x) > 
>>>> (x - 1)
>>>> over it.
>>>
>>> I'm not sure why do you test against x - 1 when you could 
>>> test for
>>> equality. Not only it looks like it is going to require an 
>>> extra
>>> computation (x - 1) but also it doesn't work for 0.
>>
>> So if you do (x & -x) == x that returns 1 for x == 0. For many 
>> applications you
>> want to yield 0. So you test for (x & -x) > (x - 1) such that 
>> for x == 0 the
>> right hand side is a large number. -- Andrei
>
> This sort of stuff should go on wiki.dlang.org page!

Please no cmp.
Just
bool isPowerOf2(uint x) { return x && !(x & (x - 1)); }