X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=Data%2FTree.hs;h=e0a7cb6de2f6d9eba90052c06378bddc8f979c99;hb=641f8d5964b2b02f4cd7b9081adf6596c6f4d4d7;hp=5a304705e62fd1a4c203867f9491125facb3ac59;hpb=13e58f0482069d84b89d90eeeeca2c172c3e6682;p=ghc-base.git

diff --git a/Data/Tree.hs b/Data/Tree.hs
index 5a30470..e0a7cb6 100644
--- a/Data/Tree.hs
+++ b/Data/Tree.hs
@@ -28,9 +28,13 @@ module Data.Tree(
 import Prelude
 #endif
 
+import Control.Applicative (Applicative(..))
 import Control.Monad
-import Data.Sequence (Seq, empty, singleton, (<|), (|>), fromList, toList,
+import Data.Monoid (Monoid(..))
+import Data.Sequence (Seq, empty, singleton, (<|), (|>), fromList,
 			ViewL(..), ViewR(..), viewl, viewr)
+import Data.Foldable (Foldable(foldMap), toList)
+import Data.Traversable (Traversable(traverse))
 import Data.Typeable
 
 #include "Typeable.h"
@@ -57,6 +61,12 @@ instance Functor Tree where
 mapTree              :: (a -> b) -> (Tree a -> Tree b)
 mapTree f (Node x ts) = Node (f x) (map (mapTree f) ts)
 
+instance Traversable Tree where
+  traverse f (Node x ts) = Node <$> f x <*> traverse (traverse f) ts
+
+instance Foldable Tree where
+  foldMap f (Node x ts) = f x `mappend` foldMap (foldMap f) ts
+
 -- | Neat 2-dimensional drawing of a tree.
 drawTree :: Tree String -> String
 drawTree  = unlines . draw