Re: Proposal: improve the Data.Tree API

Hey, So, proposal 2.0, with the received feedback: -- | get the sub-tree rooted at the first (left-most, depth-first) occurrence -- of the specified node value lookupTree :: Eq a => a -> Tree a -> Maybe (Tree a) -- | get the sub-tree rooted at the first (left-most, depth-first) value that -- matches the provided condition findTree :: (a -> Bool) -> Tree a -> Maybe (Tree a) -- | get the sub-tree for the specified node value in the first tree in -- forest in which it occurs. lookupTreeInForest :: Eq a => a -> [Tree a] -> Maybe (Tree a) -- | keep only the elements that match the provided condition filter :: (a -> Bool) -> Tree a -> Tree a -- | Size of the (flattened) tree size :: Tree a -> Int size = getSum . F.foldMap (const $ Sum 1) -- | Maximum depth of tree maxDepth :: Tree a -> Int -- | Remove all nodes past a certain depth prune :: Int -> Tree a -> Tree a -- | Take the mirror-image of a tree mirror :: Tree a -> Tree a mirror (Node a ts) = Node a . reverse $ map mirror ts Any additions / comments? Thanks, João 2014-02-24 12:55 GMT+00:00 João Cristóvão :

Hi Ivan,

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then what about the arguably better name `size`? Huh, I thought we already had that.

We do? If there is consensus I would then add `size` with the arguably more efficient implementation: size :: Tree a -> Int size = getSum . F.foldMap (const $ Sum 1)

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* An Ord instance (achievable via standalone deriving, though this isn't ideal)

Agreed.

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* Functions to take/drop so many levels of the tree (take is relatively easy; drop would result in a Forest).

Similar to treeprune in http://hackage.haskell.org/package/hledger-lib-0.22.1/docs/Hledger-Utils.htm... ?

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mirror :: Tree a -> Tree a mirror (Node a ts) = Node a . reverse $ map mirror ts

I don't have strong feeling about this one, but if more people see as useful, why not...

João

2014-02-24 11:38 GMT+00:00 Ivan Lazar Miljenovic :

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On 24 February 2014 22:17, Tobias Florek wrote:

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hi,

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But to be honest, I don't have strong feelings about this, I'm willing to drop this particular function (length) from the proposal, if there is no consensus.

then what about the arguably better name `size`?

Huh, I thought we already had that.

Some things I missed when I last used Data.Tree:

* An Ord instance (achievable via standalone deriving, though this isn't ideal)

* A function to take the mirror-image of a tree (name not that important):

mirror :: Tree a -> Tree a mirror (Node a ts) = Node a . reverse $ map mirror ts

* Functions to take/drop so many levels of the tree (take is relatively easy; drop would result in a Forest).

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cheers, tobias florek

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-- Ivan Lazar Miljenovic Ivan.Miljenovic@gmail.com http://IvanMiljenovic.wordpress.com _______________________________________________ Libraries mailing list Libraries@haskell.org http://www.haskell.org/mailman/listinfo/libraries