module Hope.Util.Tree where

import Control.Monad (liftM2)
import Data.Tree

prune :: Int -- ^ Maximum depth of nodes to keep. 0 means to keep only
             --   the root node.
      -> Tree a -> Tree a
prune 0 (Node x _)  = Node x []
prune n (Node x cs) = Node x (map (prune (n-1)) cs)

fmapMTree :: Monad m => (a -> m b) -> Tree a -> m (Tree b)
fmapMTree f (Node x xs) = liftM2 Node (f x) (mapM (fmapMTree f) xs)

-- | Reverses the order of the children of each node in the tree.
reverseTree :: Tree a -> Tree a
reverseTree t = t { subForest = reverse (map reverseTree (subForest t)) }