John_x thinks Mary_y said he_x likes her_y.
- See her 1999 paper for details.
+ See her 1999 paper for details. Essentially, she ends up layering several
+Reader monads over each other.
Here is [[code for the arithmetic tree Chris presented in week 8|code/arith1.ml]]. It computes
`\n. (+ 1 (* (/ 6 n) 4))`. Your task is to modify it to compute