op"><p>Use with care, passed environment cannot be empty. </p></td></tr>
</table></div>
<p>
</p>
</li>
<li class="listitem">
<pre class="literallayout"><a class="link" href="basic_environment/entry_type.html" title="Struct template entry_type">entry_type</a> <a name="idp51506432-bb"></a><span class="identifier">at</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">string_type</span> <span class="special">&amp;</span> key<span class="special">)</span><span class="