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LSLeary/IFix.hs

Last active May 23, 2022 23:18
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IFix.hs
{-# LANGUAGE PolyKinds, RankNTypes, TypeOperators #-}
module IFix where
newtype IFix f t = IFix (f (IFix f) t)
type f ~> g = forall x. f x -> g x
class NFunctor f where
nmap :: g ~> h -> f g ~> f h
cata :: NFunctor f => f g ~> g -> IFix f ~> g
cata alg (IFix f) = alg (nmap (cata alg) f)
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