Appender and CTFE

[spir]

On 03/03/2011 05:03 PM, Andrei Alexandrescu wrote:
> On 3/3/11 8:34 AM, Steven Schveighoffer wrote:
>> On Thu, 03 Mar 2011 07:41:49 -0500, Trass3r <un at known.com> wrote:
>>
>>> replace() doesn't work in CTFE anymore cause it was modified to be
>>> based on Appender.
>>> According to klickverbot, other phobos functions share that fate.
>>>
>>> I think something should be done about this. Couldn't Appender be
>>> implemented without using a pointer to a struct?
>>
>> Yes, it is something I intend to do. I want to make an (un at safe) scoped
>> appender which does not use a pImpl, along with a safe appender which
>> does use pImpl.
>>
>> It should be as easy as making the impl struct a public struct.
>>
>> -Steve
>
> One broader question would be if Appender's optimization is still needed after
> Steve's improvements to ~=. What is the current performance gap between using
> ~= and Appender?

When I tried to use Appender, it was actually slightly slower than plain ~=. 
The reason was, IIRC, Appender is only efficient when bits added are simple 
elements, not mini-arrays to be concatenated (there was a thread about that). 
There was also an issue with reserve.

Denis
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