dentifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special">&lt;</span> <span class="identifier">index_type</span><span class="special">,</span> <span class="identifier">index_type</span> <span class="special">&gt;</span> <a class="link" href="category.html#idm14164-bb"><span class="identifier">update</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">value_type</span> <span class="special">&amp;</span><span c