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danidiaz/AKindClass.hs

Created January 18, 2019 18:49
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kind class example
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AKindClass.hs
{-# LANGUAGE RankNTypes, DataKinds, TypeInType, PolyKinds, FlexibleInstances #-}
import Data.Proxy
import GHC.TypeLits
class Foo k
class Foo k => Bar (a :: k) where
baz :: Proxy a -> String
instance Foo k => Bar (a :: k) where
baz _ = "baz"
instance Foo Nat
printMsg :: forall (x :: Nat) . Proxy x -> IO ()
printMsg p = print $ baz p
main :: IO ()
main = return ()
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