</pre>
<p>Returns a token which uniquely identifies this regular expression. </p>
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<pre class="literallayout"><span class="keyword">void</span> <a name="idp114734496-bb"></a><span class="identifier">swap</span><span class="special">(</span><a class="link" href="basic_regex.html" title="Struct template basic_regex">basic_regex</a><span class="special">&lt;</span> <span class="identifier">BidiIter</span> <span class="special">&gt;</span> <span class="special">&amp;</span> that<span 