Hello everybody, I'm discovering boost::multi_index, and something strikes me: I've been dreaming of something like boost::multi_index key extractors (and especially member) for most of my std::set or std::sort uses. I therefore think that this part of boost::multi_index does not belong in this library, but is more general purpose, and deserves a library of its own, along with a way to get a suitable less predicate from the result of those. All the arguments that make such a framework usefull for boost::multi_index can equally be applied to STL containers and algorithms. I wonder if such a proposal has already been made (maybe it even already exists, boost has so many parts that I may be unaware of this), and in the positive case what were the arguments in favor or in opposition of it. Best regards, -- Loïc