<span class="special">,</span> <span class="identifier">node_ptr</span> header1<span class="special">,</span> <span class="identifier">node_ptr</span> node2<span class="special">,</span> 
                       <span class="identifier">node_ptr</span> header2<span class="special">)</span><span class="special">;</span></pre>
<p><span class="bold"><strong>Requires</strong></span>: node1 and node2 can't be header nodes of two trees with header header1 and header2.</p>
<p><span class="bold"><strong>Effects</str