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{-# LANGUAGE GADTs, TypeOperators, DataKinds, TypeFamilies, PolyKinds, TypeFamilyDependencies #-}
module T14749 where
import Data.Kind
data KIND = STAR | KIND :> KIND
data Ty :: KIND -> Type where
TMaybe :: Ty (STAR :> STAR)
TApp :: Ty (a :> b) -> (Ty a -> Ty b)
type family IK (k :: KIND) = (res :: Type) where
IK STAR = Type
IK (a:>b) = IK a -> IK b
type family I (t :: Ty k) = (res :: IK k) where
I TMaybe = Maybe
I (TApp f a) = (I f) (I a)
data TyRep (k :: KIND) (t :: Ty k) where
TyMaybe :: TyRep (STAR:>STAR) TMaybe
TyApp :: TyRep (a:>b) f -> TyRep a x -> TyRep b (TApp f x)
zero :: TyRep STAR a -> I a
zero x = case x of
TyApp TyMaybe _ -> Nothing
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