Then we lift the entire computation into the monad by applying ⇧ to
the integers, and by applying `map1` to the operators:
+<pre>
\tree ((((map2 +) (⇧1)) (((map2 *) (((map2 /) (⇧6)) (⇧0))) (⇧4))))
___________________
___|____ ⇧0
| |
map2 / ⇧6
+</pre>
With these adjustments, the faulty computation now completes smoothly: