span> x );</tt></p>
<blockquote>
<ul class="simple">
<li>Effects: <tt class="docutils literal">return replace( idx, x.release() );</tt></li>
</ul>
</blockquote>
</li>
<li><p class="first"><tt class="docutils literal">bool is_null( size_type idx ) const;</tt></p>
<blockquote>
<ul class="simple">
<li>Requirements: <tt class="docutils literal">idx &lt; size()</tt></li>
<li>Effects: returns whether the pointer at index <tt class="docutils literal">idx</tt> is null</li>
<li>Exception safety: Nothrow guarantee</l