module Control.Comonad.Trans.Store.Lazy
(
Store, store, runStore
, StoreT(..), runStoreT
, pos
, seek, seeks
, peek, peeks
) where
import Control.Comonad
import Control.Comonad.Hoist.Class
import Control.Comonad.Trans.Class
import Data.Functor.Identity
#ifdef __GLASGOW_HASKELL__
import Data.Typeable
instance (Typeable s, Typeable1 w) => Typeable1 (StoreT s w) where
typeOf1 dswa = mkTyConApp storeTTyCon [typeOf (s dswa), typeOf1 (w dswa)]
where
s :: StoreT s w a -> s
s = undefined
w :: StoreT s w a -> w a
w = undefined
instance (Typeable s, Typeable1 w, Typeable a) => Typeable (StoreT s w a) where
typeOf = typeOfDefault
storeTTyCon :: TyCon
storeTTyCon = mkTyCon "Control.Comonad.Trans.Store.Lazy.StoreT"
#endif
type Store s = StoreT s Identity
store :: (s -> a) -> s -> Store s a
store f s = StoreT (Identity f) s
runStore :: Store s a -> (s -> a, s)
runStore ~(StoreT (Identity f) s) = (f, s)
data StoreT s w a = StoreT (w (s -> a)) s
runStoreT :: StoreT s w a -> (w (s -> a), s)
runStoreT ~(StoreT wf s) = (wf, s)
instance Functor w => Functor (StoreT s w) where
fmap f ~(StoreT wf s) = StoreT (fmap (f .) wf) s
instance Extend w => Extend (StoreT s w) where
duplicate ~(StoreT wf s) = StoreT (extend StoreT wf) s
extend f ~(StoreT wf s) = StoreT (extend (\wf' s' -> f (StoreT wf' s')) wf) s
instance Comonad w => Comonad (StoreT s w) where
extract ~(StoreT wf s) = extract wf s
instance ComonadTrans (StoreT s) where
lower ~(StoreT f s) = fmap ($s) f
instance ComonadHoist (StoreT s) where
cohoist ~(StoreT f s) = StoreT (Identity (extract f)) s
pos :: StoreT s w a -> s
pos (StoreT _ s) = s
seek :: Comonad w => s -> StoreT s w a -> StoreT s w a
seek s ~(StoreT f _) = StoreT f s
seeks :: Comonad w => (s -> s) -> StoreT s w a -> StoreT s w a
seeks f ~(StoreT g s) = StoreT g (f s)
peek :: Comonad w => s -> StoreT s w a -> a
peek s (StoreT g _) = extract g s
peeks :: Comonad w => (s -> s) -> StoreT s w a -> a
peeks f ~(StoreT g s) = extract g (f s)