Re: [Haskell-cafe] Growing Trees

[Previously sent only to the OP -- oops] Tom Hawkins wrote:

data Tree a = TreeRoot { stuff :: a , children :: [Tree] } | TreeNode { stuff :: a , parent :: Tree , children :: [Tree] }

But because of these bidirectional links, every time I add a node I must reconstructing the entire tree.

If you don't want to use IORefs or STRefs, you could try The Zipper: http://www.haskell.org/hawiki/TheZipper or you could represent the tree as type Tree a = Data.Map.Map Int (Node a) data Node a = TreeRoot { stuff :: a, children :: [Int] } | TreeNode { stuff :: a, parent :: Int, children :: [Int] } -- Ben