"Class template unordered_set_base_hook">unordered_set_base_hook</a> in order to store objects in in an unordered_set/unordered_multi_set. <a class="link" href="unordered_set_base_hook.html" title="Class template unordered_set_base_hook">unordered_set_base_hook</a> holds the data necessary to maintain the unordered_set/unordered_multi_set and provides an appropriate <a class="link" href="value_traits.html" title="Struct template value_traits">value_traits</a> class for unordered_set/unordered_multi_set.</p>