Re: [boost] "Simple C++11 metaprogramming"

If one day we have static constexpr lambdas, wouldn't we be able to use some kind of lambda meta-functions

We don't need constexpr lambdas to achieve this. We can do higher-order type computations using dependent typing. I show here how to implement boost fusion filter so it will take a lambda rather than a MPL placeholder expression: http://pfultz2.com/blog/2015/01/24/dependent-typing/ Which is based on the ideas presented by Zach Laine and Matt Calabrese several years ago at boostcon. So in essence you can write this in C++14: auto numbers = simple_filter(some_fusion_sequence, [](auto x) { return is_integral() or is_floating_point(); }); There is no `constexpr` required by the user. It all happens through dependent typing. This is how Boost.Hana works as well. Furthermore, Boost.Hana is not `constexpr`-metaprogramming(athough it makes use of `constexpr`), it is actually dependently-typed metaprogramming, which is much more powerful in current C++.

Is not that what the proposed Boost.Hana and Boost.Fit do already using a specific trick?

That trick, in general, is only used to achieve `constexpr` initialization of lambdas, which is necessary when declaring global lambdas. In can be used in other ways to allow type deduction of lambdas in a `constexpr` context. However, in general, with dependently-typed metaprogramming this isn't necessary. Paul -- View this message in context: http://boost.2283326.n4.nabble.com/Simple-C-11-metaprogramming-tp4676344p467... Sent from the Boost - Dev mailing list archive at Nabble.com.