><span class="identifier">clear</span></a><span class="special">(</span><span class="special">)</span><span class="special">;</span>
  <a class="link" href="basic_environment/entry_type.html" title="Struct template entry_type">entry_type</a> <a class="link" href="basic_environment.html#idp51506432-bb"><span class="identifier">at</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">)</spa