module Control.Comonad.Indexed where
import Control.Comonad
import Control.Arrow
import Control.Functor.Extras
import Control.Functor.HigherOrder
import Control.Functor.Indexed
import Control.Monad
class IxFunctor w => IxComonad w where
iextract :: w i i a -> a
iextend :: (w j k a -> b) -> w i k a -> w i j b
iduplicate :: IxComonad w => w i k a -> w i j (w j k a)
iduplicate = iextend id
instance Comonad w => IxComonad (LiftIx w) where
iextract = extract . lowerIx
iextend f = LiftIx . extend (f . LiftIx) . lowerIx