Dear Experts, I currently have: template <typename KEY, typename VALUE, size_t SZ> using small_flat_map = boost::container::flat_map< KEY, VALUE, std::less<KEY>, boost::container::small_vector< std::pair<KEY,VALUE>, SZ >

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This works OK, but one thing that I do with it quite often is auto i = m.upper_bound(...); m.erase(m.begin(),i); Erasing items at the start of the vector is of course the worst thing you can do for performance with a flat_map. So I was wondering if I can have a flat_map that stores its elements in the reverse order in the underlying vector. Question: can anyone think of a way to do this that doesn't require changing all of the downstream code? For a few milliseconds I thought I could just change std::less for std::greater but that reverses the externally-visible behaviour. Is there some Boost utility that can wrap the implementation vector to work in reverse? Thanks, Phil.