de> must be <code class="computeroutput">safe_link</code> or <code class="computeroutput">auto_unlink</code>.</p>
<p><span class="bold"><strong>Returns</strong></span>: true, if the node belongs to a container, false otherwise. This function can be used to test whether <code class="computeroutput">list::iterator_to</code> will return a valid iterator.</p>
<p><span class="bold"><strong>Complexity</strong></span>: Constant </p>
</li>
<li class="listitem">
<pre class="literallayout"><span class="keyword">void<