import GHC.Arr
#elif defined(__HUGS__)
import Hugs.Array
+#elif defined(__NHC__)
+import Array
#endif
-- | Functors representing data structures that can be traversed from
--
-- a suitable instance would be
--
--- > instance Traversable Tree
+-- > instance Traversable Tree where
-- > traverse f Empty = pure Empty
-- > traverse f (Leaf x) = Leaf <$> f x
-- > traverse f (Node l k r) = Node <$> traverse f l <*> f k <*> traverse f r
-- instances for Prelude types
instance Traversable Maybe where
- traverse f Nothing = pure Nothing
+ traverse _ Nothing = pure Nothing
traverse f (Just x) = Just <$> f x
instance Traversable [] where
mapM = Prelude.mapM
-#ifndef __NHC__
instance Ix i => Traversable (Array i) where
- traverse f arr = listArray (bounds arr) `fmap` traverse f (elems arr)
-#endif
+ traverse f arr = listArray (bounds arr) `fmap` traverse f (elems arr)
-- general functions