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{-# LANGUAGE DataKinds #-}
{-# LANGUAGE ExistentialQuantification #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE TypeFamilyDependencies #-}
{-# LANGUAGE PolyKinds #-}
module Main where
import Data.Kind
import Data.Proxy
import Language.Haskell.TH hiding (Type)
-- Anonymous tyvar binder example
newtype Foo1 = Foo1 (Proxy '[False, True, False])
-- Required (dependent) tyvar binder example
type family Wurble k (a :: k) :: k
newtype Foo2 a = Foo2 (Proxy (Wurble (Maybe a) Nothing))
-- Non-injective type family example
type family Foo3Fam1 (a :: Type) :: Type where
Foo3Fam1 a = a
type family Foo3Fam2 (a :: Foo3Fam1 b) :: b
newtype Foo3 = Foo3 (Proxy (Foo3Fam2 Int))
-- Injective type family example
type family Foo4Fam1 (a :: Type) = (r :: Type) | r -> a where
Foo4Fam1 a = a
type family Foo4Fam2 (a :: Foo4Fam1 b) :: b
newtype Foo4 = Foo4 (Proxy (Foo4Fam2 Int))
$(return [])
main :: IO ()
main = do
putStrLn $(reify ''Foo1 >>= stringE . pprint)
putStrLn $(reify ''Foo2 >>= stringE . pprint)
putStrLn $(reify ''Foo3 >>= stringE . pprint)
putStrLn $(reify ''Foo4 >>= stringE . pprint)
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