an> <span class="identifier">node_ptr</span> <span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
  <span class="keyword">static</span> <span class="identifier">node_ptr</span> <a class="link" href="avltree_algorithms.html#idp56924464-bb"><span class="identifier">prev_node</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">node_ptr</span> <span class="special">&amp;</span><span class="special">)</span><span class="spe