on Thu Sep 27 2012, Matt Calabrese <rivorus-AT-gmail.com> wrote:
Hey everyone,
It's been a while since I've made an appearance on this list,
Hey, good to hear from you; welcome back!
but I was contacted regarding the recent discussion of concepts here and Lorenzo's taking the reins of a concept library, and decided to poke my head in. First, I apologize to the community for not getting Boost.Generic on the sandbox earlier (if you are unfamiliar with Boost.Generic, see my 2011 BoostCon talk http://blip.tv/boostcon/boost-generic-concepts-without-concepts-5262126 and/or the corresponding slides https://github.com/boostcon/2011_presentations/raw/master/thu/Boost.Generic.... ). I've gotten numerous emails about it since 2011 and I decided to commit the current state of Boost.Generic to the sandbox today.
Thanks!
It is still based on the "old" concepts of C++0x with pseudo-signatures. You can find it in the "generic" subdirectory of the sandbox. That said, I'm not sure anyone even cares about Boost.Generic anymore given that the standard seems to be diverging from how it originally was approaching concepts,
I would not draw too many conclusions from the recent EWG proposals. It remains unclear to many of us that the "valid expressions" approach is technically or ergonomically feasible.
but here it is anyway. Similarly, I'm not sure there is any interest from people for me to continue developing Boost.Generic, so I guess this is a check for interest again.
+1
And, very briefly, without getting too political here (not that my opinion has any bearing) but I personally do not agree with some of the recent design changes for what may turn out to be C++1y concepts -- specifically I think pseudo-signatures were better overall and the C++0x form of associated types was much more useful than what is currently described, especially concerning associated type deduction, which no longer appears to be possible. But I don't think this discussion is suitable for the Boost mailing list and I don't want to ruffle too many feathers beyond that, so I'll take that elsewhere.
You should bring it to https://groups.google.com/a/isocpp.org/forum/?fromgroups#!forum/std-discussi... or https://groups.google.com/a/isocpp.org/forum/?fromgroups#!forum/std-proposal....
For this reason, though, I [currently] do not have a desire to support that form of concepts in my library, though I do plan to resume work on Boost.Generic.
+1
A recap of what's gone on since my Boostcon talk, for anyone who even remembers it -- I haven't been actively developing Boost.Generic for over a year as I have been busy with other things, but coincidentally in the past couple of weeks I've gone back to it and decided to update some things due to a trick I realized I could use to get full compatibility with the C++0x working paper for explicit concept map templates (N2914's 14.10.3.2 paragraph 3 highlights why it's non-trivial, see http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2009/n2914.pdf).
? That seems to cover implicit (not explicit) concept maps: 14.10.3.2 Implicit concept maps for refined concepts [concept.refine.maps]
Since then, I've had renewed interest in the project and have updated various facilities. Stuff that changed since my presentation back in 2011 -- it now supports variadic concepts using the syntax ,,, (see
So clever. -- Dave Abrahams BoostPro Computing Software Development Training http://www.boostpro.com Clang/LLVM/EDG Compilers C++ Boost