While catching up on recent postings to Lambda the Ultimate, I was rather surprised to discover that last week concepts were, by a vote of the committee members, completely removed from the C++0x draft specification.
On Monday, July 13th 2009 Concepts were dramatically voted out of C++0x during the C++ standards committee meeting in Frankfurt. [...] When I first heard the news, I couldn’t believe it. Concepts were supposed to be the most important addition to core C++ since 1998. Tremendous efforts and discussions were dedicated to Concepts in every committee meeting during the past five years. After dozens of official papers, tutorials and articles — all of which were dedicated to presenting and evangelizing Concepts — it seemed very unlikely that just before the finishing line, Concepts would be dropped in a dramatic voting.
C++0x is the next version of the C++ language standard. It should more properly be called C++1x, since the chances of it being released within the year are like the chances that Microsoft would contribute code to the Linux kernel — er, bad example. Anyway, the point is that it’s not going to be done this year.
While I’ve been following the development of C++0x with interest, I haven’t been immersing myself in the implementation details. In essence, I want to know what’s coming up, but I’m not too interested in committing to memory the nuts and bolts of a specification that is likely to be revised several more times before it is finalized. I’m not totally abstaining from C++0x until it’s done. I do use some features where they are useful and already implemented, for example I am using unordered_map, the standard library’s version of a hash table, in the latest iteration of my work on the lottery problem. However, my understanding of the majority of C++0x features has been relatively, for lack of a better word, “conceptual”.
The layman’s understanding that I had of the C++0x concepts feature led me to react with shock to learning of it’s removal. It sounded incredibly useful, and I didn’t see what could be such a big problem that it would have to be ripped out entirely. That changed when I read more about concepts as they (were going to) exist in C++0x.