[Haskell-beginners] Finding the height of a simple binary tree

Rahul Kapoor rk at trie.org
Thu Dec 24 20:34:35 EST 2009

See if this case analysis helps:

Height of the Empty Node is zero.
Height of a non empty node is = 1 + (the greater height of its 2 sub trees)

The function max gives you the greater of two values.


On Thu, Dec 24, 2009 at 8:18 PM, Matt Young <mabufo at gmail.com> wrote:
> Hi guys! Just so we are all on the same page, this problem is an
> exercise from the end of Chapter 3 in the book Real World Haskell
> (#8).
> The problem calls for me to write a function to figure out the height
> of our user defined binary tree type.
> Here is the type:
>  --chapter3 binary tree recursive type
> data Tree a = Node a (Tree a) (Tree a)
>                          | Empty
>                                deriving (Show)
> With this type, we'd create a tree with no leaves like: Node "tree"
> Empty Empty, and a tree with a single leaf like Node "tree2" = Empty
> (Node "leaf" Empty Empty)
> Being new to Haskell, I'm not sure how to traverse this binary tree
> type that the book has given. No doubt we'll be using some crafty
> recursion to get this done. So to summarize what I'd like to know, 1)
> what is the best way to figure out the height of this binary tree type
> that I have, or rather any binary tree in general? 2) How do I
> translate that into Haskell code.
> Verbose explanations are appreciated.
> Thanks guys!
> --
> -Matthew
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