Thank you Bob,
your example clarified how actually using such data type would appear in
haskell. I naively thought it would be as simple as defining a regular list,
but i see it is slightly more strict than that. I appreciate your help!
Vadali
On Tue, Jul 13, 2010 at 11:18 AM, Thomas Davie
On 13 Jul 2010, at 10:11, Shlomi Vaknin wrote:
Thank you all for replying!
I am really beginning my baby steps in this fascinating language, and was just wondering if it was possible to naturally scan lists with arbitrary lists (aka trees :) ).
Trees aren't lists, Trees are trees... Here's how you create one*
data Tree a = Leaf | Branch a [Tree a]
This roughly says, a tree can be made up of two possible things... First, it could be a leaf, and secondly, it could be a branch with an element at it, and a list of subtrees.
Some example trees using this data type:
1) Leaf 2) Branch 5 [] 3) Branch 5 [Leaf] 4) Branch 5 [Branch 10 [], Branch 20 [], Leaf, Branch 50 [Branch 10 [], Leaf]]
When you have really strong typing, you also have very well specified types. You don't just use a list as if it were a tree, you declare what a tree is.
Bob
* In this case an arbitrarily branching tree, we could ofc declare different forms of tree here.