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{-# LANGUAGE TypeFamilies #-}
module T8518 where
import Data.Maybe
import Control.Applicative
class Continuation c where
type Z c
type B c
type F c
continue :: c -> (Z c) -> (B c) -> Maybe ((F c), c)
callCont :: Continuation c => c -> (Z c) -> (B c) -> Maybe (F c)
callCont c z b = rpt (4 :: Int) c z b
where
rpt 0 c' z' b' = fromJust (fst <$> (continue c' z' b'))
rpt i c' z' b' = let c'' = fromJust (snd <$> (continue c' z' b')) in rpt (i-1) c''
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