Re: [boost] Enabling fast swap optimization for Boost types VC9 SP1.

From: Michael Marcin (mike.marcin_at_[hidden])
Date: 2008-08-27 14:48:04

David Abrahams wrote:
> on Wed Aug 27 2008, "Niels Dekker - mail address until 2008-12-31" <nd_mail_address_valid_until_2008-12-31-AT-xs4all.nl> wrote:
> 
>> David Abrahams wrote:
>>> What was wrong with my proposal?
>>>
>>> You can't guarantee it will be right every time, but it's easy to
>>> correct when wrong, and that would only take a very few
>>> specializations.
>> Please note: The question is /not/ whether T has a custom swap. The
>> question is whether default-construction + swap outperforms
>> copy-construction for type T. Only in that case, it makes sense to
>> activate "Swaptimization".
> 
> Of course.  But can you come up with a type where it makes sense to have
> written a custom swap but default-construction + swap won't outperform
> copy construction?  Maybe my imagination is failing me, but I can't.
> 

Isn't this the case for the current boost::function?

Also a type could be Swappable and Assignable but not Default Constructible.

Thanks,

Michael Marcin