ier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special">&lt;</span> <span class="identifier">iterator</span><span class="special">,</span> <span class="keyword">bool</span> <span class="special">&gt;</span> 
  <a class="link" href="iunordered_set_index.html#idp55202832-bb"><span class="identifier">insert_check</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">intrusive_compare_key_type</span> <span class="speci