Beginning Haskell - getting “not in scope: data constructor” error

Question

I\'m going through the problems in the Haskell O\'Reilly book. The problem I am working on is

Using the binary tree type that we defined earlier in this chapter         


        

Answer 1

You pattern-match against constructors, i.e. the cases, of your Tree ADT. Tree is just what sums them all up.

It's much more straightforward like this, and, most of all, correct:

height Empty = 0
height (Node _ l r) = 1 + max (height l) (height r)