title: C++ <map> vs <unordered_map> vs <tr1/unordered_map> vs <ext/unordered_map>
body: <p>I'm currently looking for a better alternative to std::map and have come across classes mentioned in the post title. Could someone clarify the differences between them, not in terms of performance/API, but in terms of where they beleong in relation to the current and forthcomnig standard.</p>