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-- Check that we can implement abstract data using a data family.
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE TypeFamilies #-}
unit p where
signature H where
import Data.Kind
type T :: Bool -> Type
data T b
turnOff :: T True -> T False
turnOn :: T False -> T True
module A where
import H
foo :: T True -> T True
foo = turnOn . turnOff
unit q where
module H where
import Data.Kind
type D :: Bool -> Type
data family D a
data instance D True = DT
data instance D False = DF
turnOff DT = DF
turnOn DF = DT
type S = D
type T = S
unit r where
dependency q
dependency p[H=q:H]
module N where
import A
bar = foo . foo
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