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Prototype Haskell Fix Traversal combinator
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{-# LANGUAGE PartialTypeSignatures #-} | ||
module Plutarch.CPS.Optics.Fix(fixt) where | ||
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import Data.Fix | ||
import Control.Lens | ||
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import Data.Functor.Base | ||
import Data.Function | ||
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fixt :: | ||
(Applicative f) => | ||
(forall ra rb. (ra -> f rb) -> a ra -> f (b rb)) -> | ||
Fix a -> | ||
f (Fix b) | ||
fixt f = fmap Fix . (fix (f . dimap unFix (fmap Fix))) . unFix | ||
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list' :: Traversal (Fix (ListF a)) (Fix (ListF b)) a b | ||
list' f = fixt (listf f) | ||
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listf :: | ||
(Applicative f) => | ||
(a -> f b) -> | ||
(ra -> f rb) -> | ||
ListF a ra -> | ||
f (ListF b rb) | ||
listf _ _ Nil = pure Nil | ||
listf f r (Cons a b) = Cons <$> f a <*> r b |
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