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{-# LANGUAGE KindSignatures #-}
module T12425 where
import Control.Applicative
import Control.Monad
import Control.Monad.Trans.State.Lazy (StateT(..))
data Result a m b = RecurseOnly (Maybe (CondT a m b))
| KeepAndRecurse b (Maybe (CondT a m b))
instance Monad m => Functor (Result a m) where
fmap f (RecurseOnly l) = RecurseOnly (liftM (fmap f) l)
fmap f (KeepAndRecurse a l) = KeepAndRecurse (f a) (liftM (fmap f) l)
{-# INLINE fmap #-}
newtype CondT a m b = CondT (StateT a m (Result a m b))
instance Monad m => Functor (CondT a m) where
fmap f (CondT g) = CondT (liftM (fmap f) g)
{-# INLINE fmap #-}
instance Monad m => Applicative (CondT a m) where
pure = undefined
(<*>) = undefined
instance Monad m => Monad (CondT a m) where
return = undefined
(>>=) = undefined
-- liftM :: (Monad m) => (a1 -> r) -> m a1 -> m r
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