import Prelude
#endif
+import Control.Applicative (Applicative(..), (<$>))
import Control.Monad
-import Data.Sequence (Seq, empty, singleton, (<|), (|>), fromList, toList,
+import Data.Monoid (Monoid(..))
+import Data.Sequence (Seq, empty, singleton, (<|), (|>), fromList,
ViewL(..), ViewR(..), viewl, viewr)
+import Data.Foldable (Foldable(foldMap), toList)
+import Data.Traversable (Traversable(traverse))
import Data.Typeable
-#include "Typeable.h"
+#ifdef __GLASGOW_HASKELL__
+import Data.Generics.Basics (Data)
+#endif
-- | Multi-way trees, also known as /rose trees/.
data Tree a = Node {
subForest :: Forest a -- ^ zero or more child trees
}
#ifndef __HADDOCK__
+# ifdef __GLASGOW_HASKELL__
+ deriving (Eq, Read, Show, Data)
+# else
deriving (Eq, Read, Show)
+# endif
#else /* __HADDOCK__ (which can't figure these out by itself) */
instance Eq a => Eq (Tree a)
instance Read a => Read (Tree a)
instance Show a => Show (Tree a)
+instance Data a => Data (Tree a)
#endif
type Forest a = [Tree a]
+#include "Typeable.h"
INSTANCE_TYPEABLE1(Tree,treeTc,"Tree")
instance Functor Tree where
- fmap = mapTree
+ fmap f (Node x ts) = Node (f x) (map (fmap f) ts)
+
+instance Traversable Tree where
+ traverse f (Node x ts) = Node <$> f x <*> traverse (traverse f) ts
-mapTree :: (a -> b) -> (Tree a -> Tree b)
-mapTree f (Node x ts) = Node (f x) (map (mapTree 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
-- | The elements of a tree in pre-order.
flatten :: Tree a -> [a]
flatten t = squish t []
- where squish (Node x ts) xs = x:foldr squish xs ts
+ where squish (Node x ts) xs = x:Prelude.foldr squish xs ts
-- | Lists of nodes at each level of the tree.
levels :: Tree a -> [[a]]
#ifndef __NHC__
unfoldForestM :: Monad m => (b -> m (a, [b])) -> [b] -> m (Forest a)
#endif
-unfoldForestM f = mapM (unfoldTreeM f)
+unfoldForestM f = Prelude.mapM (unfoldTreeM f)
-- | Monadic tree builder, in breadth-first order,
-- using an algorithm adapted from
EmptyL -> return empty
a :< aQ -> do
(b, as) <- f a
- tQ <- unfoldForestQ f (foldl (|>) aQ as)
+ tQ <- unfoldForestQ f (Prelude.foldl (|>) aQ as)
let (tQ', ts) = splitOnto [] as tQ
return (Node b ts <| tQ')
where splitOnto :: [a'] -> [b'] -> Seq a' -> (Seq a', [a'])