C++1x loses Concepts

Bjarne Stroustrup and Herb Sutter have both reported on the ISO C++ meeting in Frankfurt a week ago, in which the much-heralded feature "concepts" were removed from C++1x.

Concepts are a powerful feature aimed at improving overloading (basically, removing the extra work in using things like iterator categories) and moving type checking up the ladder so that more reasonable error messages can be produced when a developer passes in the wrong type (think a single error line instead of multiple pages of template crap). Apparently the feature was a lot less solid than most of us thought, with a huge amount of internal arguing within the committee on a lot of the fundamental features of it. It seems that while most agreed concepts were a good idea, nobody could agree on how to implement them.

I'm definitely disappointed by this, but I'm also glad they chose to remove concepts instead of further delaying the standard, or worse putting out a poorly designed one. Instead, it seems like there is hope for a smaller C++ update to come out in 4-5 years that adds a more well thought out concepts feature. There are plenty of other C++1x language features to be happy about for though, like variadic templates, rvalue references, and lambda functions!

You may notice I've been saying C++1x here instead of C++0x—that's because it's pretty obvious to everyone now that we won't be getting the next C++ standard in 2009, but more likely 2011 or 2012. Just in time for the end of the world!

Posted on July 22, 2009 in C++, C++0x, C++11, Coding

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