Please state clearly whether you think this library should be accepted as a Boost library.
Yes. I vote to accept.
Other questions you may want to consider: 1. What is your evaluation of the design?
Outstanding.
2. What is your evaluation of the implementation?
Haven't looked.
3. What is your evaluation of the documentation?
I just skimmed through the docs to get what I need (see below). It would be good to have examples at the bottom of each of the reference sections like that of MPL, Fusion and the PPlib. Example: http://www.boost.org/doc/libs/1_50_0/libs/mpl/doc/refmanual/fold.html At the bottom, we have an example.
4. What is your evaluation of the potential usefulness of the library?
Extremely useful!
5. Did you try to use the library? With what compiler? Did you have any problems?
Yes. I tried to use it as a replacement for Boost.Function in Boost.Spirit. It worked like a charm. My only difficulty was in trying to figure out how to detect a default-initialized 'any'. With Boost.Function, you can use an instance in a condition, e.g. if (f) ... This seems to be not the case with 'any'. I'm pretty sure this is something simple to do, but I can't dig it out in the docs. I ended up casting to void*. It turns out that it returns 0 (null) if any hasn't been initialized yet. I'm not sure about the cost of that though (would that have to use RTTI? It seems that way as it says in the any_cast docs: http://tinyurl.com/d8sx46m where it says that typeid_ is required. I did a CT test on one of the largest examples in spirit. I compared it against 1) the original implementation using Boost.Function and 2) A hand-coded implementation using virtual functions. Here are the results: TypeErasure: 01:14 secs Boost.Function: 00:55 secs Virtual Function: 00:52 secs For that matter, I'm not ready to use TypeErasure yet for my purpose, but I'm hoping that Steven can improve CT. It might also be possible that I am using TypeErasure incorrectly when I resort to any_cast to test for null any. Would this explain the CT slowdown? I am not sure. I'd also suggest the addition of an easy to use Boost.Function replacement in there that can be used out of the box with full compliance. I know this is merely scratching the surface, but I am sure I'll be using TypeErasure's more powerful features.
6. How much effort did you put into your evaluation? A glance? A quick reading? In-depth study?
A few hours of study.
7. Are you knowledgeable about the problem domain?
I believe so. Regards, -- Joel de Guzman http://www.boostpro.com http://boost-spirit.com