and the new node which reflect
  the changes, is required.
  All nodes are assumed to NOT be node pairs, (before and after).</p>

<h3 class="function"><a name="index_by-2">index_by/2</a></h3>
<div class="spec">
<p><tt>index_by(Fun::fun((Node) -&gt; Idx), Tree::<a href="#type-tree">tree()</a>) -&gt; <a href="http://www.erlang.org/doc/man/dict.html#type-dict" target="_top">dict:dict</a>(Idx, Node)</tt>
<ul class="definitions"><li><tt>Node = <a href="tree.html#type-tree_node">tree:tree_node()</a></tt></li><li>