mplace</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">string_type</span> <span class="special">&amp;</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">string_type</span> <span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
  <span class="keyword">bool</span> <a class="link" href="basic_environment.html#idp51502400-bb"><span class="identifier">empty</span></a><span cla