The C++ standards committee met in Frankfurt, Germany, last week. Key actions: * Concepts have been removed from C++0x. The committee is very much in favor of Concepts. But Concepts are seen as so important that they have to be right. And the strong consensus was that getting Concepts right, for any reasonable definition of "right", would add several years to the schedule. There was also a consensus that an implementation of a compiler that could compile the entire standard library is part of the definition of "right". While ConceptGCC has been a great help, it isn't there as far as validating "right". Personally, I think Clang may end up being the compiler that eventually validates Concepts. * The range-based for loop and some other library features that were dependent on Concepts will be retained by recasting them to no longer depend on Concepts. See a paper in the upcoming post-meeting mailing to see how range-based for loops will work. * A second Committee Draft (CD2) will need go out for public comment in the Spring or Summer 2010, given the amount of change required to remove Concepts. The C++0x final schedule will thus slip about one year. * No committee action was taken as to how Concepts will eventually make it into C++. While there was a bit of discussion about doing a Concepts Technical Report (TR), there was no such proposal made. Committee members seem to lean toward letting the two rival Concept teams go back to work outside of the committee process. The expectation being they will come back to the committee when they are ready to restart the standardization process. Hopefully the lessons learned about Concepts during the committee process will be taken advantage of, so future standardization of Concepts will be smoother. My personal opinion is that removing Concepts will speed the arrival of conforming C++0x compilers. GCC, for example, has already implemented much of C++0x, so their key developers are no longer faced with the difficult task of turning ConceptGCC into a production compiler, and can concentrate on remaining major features like lambdas. Although Concepts would have added a lot to C++ and Boost, Concepts would also have presented major migration challenges. I'm thinking that for most Boost libraries, migration to C++0x will now be easier and less disruptive. We need to focus on the bright side. --Beman