[Haskell-beginners] Map on Nested Lists

[Tim Sears]

If you don't mind choosing a different data type (always a good  
question to ask yourself in haskell) you could simply use your own  
nested lists....

data Nested a  = One a | Nest [Nested a]
                  deriving Show

instance Functor Nested where
     fmap f (One x) = One (f x)
     fmap f (Nest xs) = Nest (map (fmap f) xs)

mapN :: (a -> b) -> Nested a -> Nested b
mapN = fmap

test =  fmap (+1) $ Nest [One 1, Nest [ One 2, One 3], One 4 , Nest  
[ Nest [One 6]] ]
--yields test = Nest [One 2,Nest [One 3,One 4],One 5,Nest [Nest [One  
7]]]



On Apr 8, 2010, at 9:05 AM, beginners-request at haskell.org wrote:

> Re: [Haskell-beginners] Map on Nested Lists

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