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ChrisPenner/DynamicComonad.hs

Created April 5, 2019 20:22
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Dynamic Programming Comonads using Recursion Schemes
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DynamicComonad.hs
import Data.Functor.Foldable
import Control.Comonad.Cofree as C
import Control.Comonad.Trans.Cofree as CF
cofreeDynExtend :: forall f a b.
Functor f
=> (CofreeF f a (C.Cofree f b) -> b)
-> C.Cofree f a
-> C.Cofree f b
cofreeDynExtend f = cata extract'
where
extract' :: CofreeF f a (C.Cofree f b) -> C.Cofree f b
extract' t@(_ CF.:< bs) = f t C.:< bs
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