is there any Phobos function to calculate the next power of 2 of the specified number?

On 10/6/12 4:48 PM, ref2401 wrote:
> is there any Phobos function to calculate the next power of 2 of the
> specified number?

Use 1U << bsr(x).

http://dlang.org/phobos/core_bitop.html#bsr


Andrei

On 07-Oct-12 00:48, ref2401 wrote:
> is there any Phobos function to calculate the next power of 2 of the
> specified number?

No though it's reinvented in a couple of places I think.

Anyway this should work for unsigned numbers:

import core.bitop;
T nextPow2(T)(T x){
	return x == 0 ? 1 : 1^^(bsr(x)+1);
}

-- 
Dmitry Olshansky

On 07-Oct-12 00:54, Dmitry Olshansky wrote:
> On 07-Oct-12 00:48, ref2401 wrote:
>> is there any Phobos function to calculate the next power of 2 of the
>> specified number?
>
> No though it's reinvented in a couple of places I think.
>
> Anyway this should work for unsigned numbers:
>
> import core.bitop;
> T nextPow2(T)(T x){
>      return x == 0 ? 1 : 1^^(bsr(x)+1);
> }

Yikes, 1<<(bsr(x)+1) or 2 ^^ (bsr(x)+1) ...
still haven't got used to 2^^x notation compared to shifts.


-- 
Dmitry Olshansky

On 10/6/12 4:54 PM, Dmitry Olshansky wrote:
> On 07-Oct-12 00:48, ref2401 wrote:
>> is there any Phobos function to calculate the next power of 2 of the
>> specified number?
>
> No though it's reinvented in a couple of places I think.
>
> Anyway this should work for unsigned numbers:
>
> import core.bitop;
> T nextPow2(T)(T x){
> return x == 0 ? 1 : 1^^(bsr(x)+1);
> }

That's right, apologies for my buggy suggestion.

Andrei

On 10/6/12 4:57 PM, Dmitry Olshansky wrote:
> On 07-Oct-12 00:54, Dmitry Olshansky wrote:
>> On 07-Oct-12 00:48, ref2401 wrote:
>>> is there any Phobos function to calculate the next power of 2 of the
>>> specified number?
>>
>> No though it's reinvented in a couple of places I think.
>>
>> Anyway this should work for unsigned numbers:
>>
>> import core.bitop;
>> T nextPow2(T)(T x){
>> return x == 0 ? 1 : 1^^(bsr(x)+1);
>> }
>
> Yikes, 1<<(bsr(x)+1) or 2 ^^ (bsr(x)+1) ...
> still haven't got used to 2^^x notation compared to shifts.

That's right, apologies for my buggy suggestion and my suggestion of a buggy suggestion :o).

Andrei

On 07-Oct-12 00:58, Andrei Alexandrescu wrote:
> On 10/6/12 4:57 PM, Dmitry Olshansky wrote:
>> On 07-Oct-12 00:54, Dmitry Olshansky wrote:
>>> On 07-Oct-12 00:48, ref2401 wrote:
>>>> is there any Phobos function to calculate the next power of 2 of the
>>>> specified number?
>>>
>>> No though it's reinvented in a couple of places I think.
>>>
>>> Anyway this should work for unsigned numbers:
>>>
>>> import core.bitop;
>>> T nextPow2(T)(T x){
>>> return x == 0 ? 1 : 1^^(bsr(x)+1);
>>> }
>>
>> Yikes, 1<<(bsr(x)+1) or 2 ^^ (bsr(x)+1) ...
>> still haven't got used to 2^^x notation compared to shifts.
>
> That's right, apologies for my buggy suggestion and my suggestion of a
> buggy suggestion :o).
>

Post of the day :)

-- 
Dmitry Olshansky

On Saturday, 6 October 2012 at 21:00:57 UTC, ref2401 wrote:
> is there any Phobos function to calculate the next power of 2 of the specified number?

See:
http://d.puremagic.com/issues/show_bug.cgi?id=6343

Bye,
bearophile