Re: Data.Tree traversals

Er... I may have mixed up preorder and depth-first -- I tend to do that. The point is, whatever it doesn't do, it should do. On Tue, Apr 21, 2015 at 12:08 AM, Dan Burton wrote:

+1 I don't see why not. Pre-order and post-order are also pretty textbook traversals. I don't imagine they'll be used very heavily, but they're certainly good for learning purposes.

Perhaps instead of newtypes for each of these, we can just provide the corresponding "traverse" function. These types unsurprisingly correspond to lens's Traversal (Tree a) (Tree b) a b.

depthFirst :: Applicative f => (a -> f b) -> Tree a -> f (Tree b) depthFirst = ...

preOrder :: Applicative f => (a -> f b) -> Tree a -> f (Tree b) preOrder = ...

postOrder :: Applicative f => (a -> f b) -> Tree a -> f (Tree b) postOrder = ...

inOrder :: Applicative f => (a -> f b) -> Tree a -> f (Tree b) inOrder = traverse

-- Dan Burton

On Mon, Apr 20, 2015 at 8:20 PM, David Feuer wrote:

...

Data.Tree makes Tree into a Traversable in only one way: depth-first. It seems to me that we should have a newtype to traverse in breadth-first order.

David Feuer

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