Checking if an Integer is an Exact Binary Power

[Andrei Alexandrescu via Digitalmars-d]

On 4/24/16 7:00 PM, Temtaime wrote:
> 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.

Why? -- Andrei