I'm the author that article and it's coincidental that I was actually thinking about gauging interest here about the library implementation of it that I'm working on. The library is coming along great and has support for C++03, full continuations, and Boost.MPL wrapper words. If there's sufficient interest I'll consider submitting it for formal review when I'm done.
It looks like TMP made easy (finally !)
"Easy" is not the correct word, but "easier" is absolutely true.
While I'm a fan of point-free programming, I think it the that comparison is not completely fair; if you allow c++11 template using syntax, then the classic MPL metafunction notation becomes:
template<typename Predicate, typename List> struct foo: add<square<length<filter<Predicate, List>>>>, int_<5>>{};
Which is almost as good as the concatenative version. The extra <> noise is annoying in this case, but in the general case where the syntax tree is more complex, the classic MPL version would actually be more readable.
You're correct, it's not a fair comparison; however, there are two additional points to consider: - 'using' syntax is a huge syntactical improvement, although from what I understand it cannot be used in higher-order metafunctions without some additional boilerplate. Not really a problem for a library though - I'd love to see Boost.MPL updated to support C++11. - Functional TMP unfortunately lacks the infix operators found in many other functional languages and thus -loses a lot of their readability. (Hopefully I sent this email correctly, I'm unfamiliar with mailing lists) -- Patrick