>contained but not equal).</p>
<dl class="section note"><dt>Note</dt><dd><ol type="1">
<li>An empty box contains nothing.</li>
<li>A non-empty box contains any empty box. </li>
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<h2 class="memtitle"><span class="permalink"><a href="#abfec0a14dd083e2c9fb721adb68122f1">&#9670;&#160;</a></span>operator&lt;()</h2>

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template&