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fronx/NestedLists.hs

Created June 23, 2014 21:49
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NestedLists.hs
module NestedLists where
data NestedList a = Nest [NestedList a] | Item a
deriving Show
nestedList = Nest [ Item 1
, Item 2
, Nest [ Item 3
, Nest [ Item 4
, Item 5
]
, Item 6
]
]
instance Functor NestedList where
fmap f (Item x) = Item (f x)
fmap f (Nest nest) = Nest ((fmap . fmap) f nest)
main = do
print $ fmap (*2) nestedList
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