Corrado Zoccolo skrev:
On Fri, Apr 11, 2008 at 9:38 AM, Sebastian Redl < sebastian.redl@getdesigned.at> wrote:
If this variant of swap() is really more efficient, perhaps metaprogramming could be used to support it *if* the type has a default constructor. But I don't know how to detect this. TypeTraits doesn't contain a has_default_constructor trait. It may be that this will only work with 09 concepts - DefaultConstructible.
We can use has_nothrow_default_constructor . This will also exclude the specialization when the default constructor performs some allocation, and could result in lower performance.
I can't imagine that it would result in lower performance in general ... have you seen many types for which default construction was more expensive than copy-construction? has_nothrow_default_constructor is certainly useable, albeit it requires compiler inrinsics. Do we know how many compilers that do support them? -Thorsten