</pre>
Notice that we've counted each internal node twice---it's a good
-excerice to adjust the code to count each node once.
+exercise to adjust the code to count each node once.
One more revealing example before getting down to business: replacing
`state` everywhere in `treemonadizer` with `list` gives us
<pre>
-# treemonadizer (fun x -> [[x; square x]]) t1;;
+# treemonadizer (fun x -> [ [x; square x] ]) t1;;
- : int list tree list =
[Node
(Node (Leaf [2; 4], Leaf [3; 9]),