Hello David, gruenedd@idmt.fraunhofer.de ha escrito:
Hello,
What is the status of key swapping, issued here[1]? Do you see a chance to have this included sometime? :]
Nothing like that has been included in Boost 1.34, and I decided to finally not implement the idea because: * It can be simulated externally (admittedly, not in an optimal fashion). * I don't see as a commonly wanted feature. * It implies weird semantics: swapping keys can result in collisions arising in other indices. Consider for instance: multi_index_container< std::pair<int,int>, indexed_by< ordered_unique<member<std::pair<int,int>,int,&std::pair<int,int>::first> >, ordered_unique<identity<std::pair<int,int> > >
c;
c.insert(std::make_pair(0,1)); c.insert(std::make_pair(1,0)); c.insert(std::make_pair(1,1)); c.swap_keys(c.begin(),++c.begin()); // would yield a duplicate element (1,1) Not that this cannot be handled, but it implies that a possible outcome of swap_keys() is that both elements get deleted or the operation rolled back, which is IMHO a little surprising to the unadvertent user. I'm sorry the answer to your proposal is negative.
Best Regards, David
On another issue, you might be interested to know that the problem you brought forward in http://lists.boost.org/Archives/boost/2005/02/80589.php has been solved in 1.34, and the very sample snippet you provided then now compiles and works cleanly. The solution does not follow your proposed approach, but uses boost::disable_if<> instead. More info at http://boost-consulting.com/boost/libs/multi_index/doc/release_notes.html#bo... (third bullet). Best regards, Joaquín M López Muñoz Telefónica, Investigación y Desarrollo