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{-# LANGUAGE LinearTypes #-}
{-# LANGUAGE UndecidableInstances, Rank2Types,
KindSignatures, EmptyDataDecls, MultiParamTypeClasses, CPP #-}
module T1735_Help.Basics where
data Proxy a = Proxy
class Data ctx a where
gunfold :: Proxy ctx
-> (forall b r. Data ctx b => c (b -> r) -> c r)
-> (forall r. r -> c r)
-> Constr
-> c a
newtype ID x = ID { unID :: x }
fromConstrB :: Data ctx a
=> Proxy ctx
-> (forall b. Data ctx b => b)
-> Constr
-> a
fromConstrB ctx f = unID . gunfold ctx k z
where
k c = ID (unID c f)
z = ID
data Constr = Constr
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