Re: [Boost-users] [multi_index] Indices interface type for overload resolution

On Wed, Nov 20, 2019 at 2:51 PM Christophe B via Boost-users < boost-users@lists.boost.org> wrote:

template std::vector<Key> keys(const std::map &m) { ... }

I'd like to write an overload that works also with the indices interface of multi_index_container.

template

std::vector<Key> keys(const std::map &m) { ... }

I suspect that you only need to make your template a little more generic, something like (untested): template <typename C> std::vector<typename C::key_type> keys(const C& c) { std::vector<typename C::key_type> result; result.reserve(c.size()); for (const auto& entry : c) { result.emplace_back(entry.first); } return result; }