)</span><span class="special">;</span></pre></li>
<li class="listitem"><pre class="literallayout"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Visitor<span class="special">&gt;</span> <span class="keyword">void</span> <a name="idp60416544-bb"></a><span class="identifier">apply_to</span><span class="special">(</span><span class="identifier">Visitor</span> <span class="special">&amp;</span><span class="special">)</span> <span class="keyword">const