n> <span class="identifier">T</span> <span class="identifier">exchange</span><span class="special">(</span><span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">t</span><span class="special">,</span> <span class="identifier">U</span><span class="special">&amp;&amp;</span> <span class="identifier">u</span><span class="special">);</span>
<span class="special">}</span>
</pre>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="core.exchange.