">old</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
<span class="special">}</span><span class="special">;</span></pre></div>
<div class="refsect1">
<a name="idm42245"></a><h2>Description</h2>
<p>By default, the implementation of this trait uses <code class="computeroutput">T's</code> copy constructor to make one single copy of the specified value. However, programmers can specialize this trait to copy old values using 