e in the linked list, as well as
which list it is in. This allows constant time <a href="dart-collection/LinkedListEntry/insertAfter.html">LinkedListEntry.insertAfter</a>,
<a href="dart-collection/LinkedListEntry/insertBefore.html">LinkedListEntry.insertBefore</a> and <a href="dart-collection/LinkedListEntry/unlink.html">LinkedListEntry.unlink</a> operations
when all you have is the element.</p>
<p>A <code>LinkedList</code> also allows constant time adding and removing at either end,
and a constant time len