module Control.Proxy.Trans.State (
StateP(..),
runStateP,
runStateK,
evalStateP,
evalStateK,
execStateP,
execStateK,
get,
put,
modify,
gets
) where
import Control.Applicative (Applicative(pure, (<*>)), Alternative(empty, (<|>)))
import Control.Monad (liftM, ap, MonadPlus(mzero, mplus))
import Control.Monad.IO.Class (MonadIO(liftIO))
import Control.Monad.Trans.Class (MonadTrans(lift))
import Control.MFunctor (MFunctor(mapT))
import Control.Proxy.Class (Channel(idT, (>->)))
import Control.Proxy.Trans (ProxyTrans(liftP))
newtype StateP s p a' a b' b (m :: * -> *) r
= StateP { unStateP :: s -> p a' a b' b m (r, s) }
instance (Monad (p a' a b' b m)) => Functor (StateP s p a' a b' b m) where
fmap = liftM
instance (Monad (p a' a b' b m)) => Applicative (StateP s p a' a b' b m) where
pure = return
(<*>) = ap
instance (Monad (p a' a b' b m)) => Monad (StateP s p a' a b' b m) where
return a = StateP $ \s -> return (a, s)
m >>= f = StateP $ \s -> do
(a, s') <- unStateP m s
unStateP (f a) s'
instance (MonadPlus (p a' a b' b m))
=> Alternative (StateP s p a' a b' b m) where
empty = mzero
(<|>) = mplus
instance (MonadPlus (p a' a b' b m)) => MonadPlus (StateP s p a' a b' b m) where
mzero = StateP $ \_ -> mzero
mplus m1 m2 = StateP $ \s -> mplus (unStateP m1 s) (unStateP m2 s)
instance (MonadTrans (p a' a b' b)) => MonadTrans (StateP s p a' a b' b) where
lift m = StateP $ \s -> lift $ liftM (\r -> (r, s)) m
instance (MonadIO (p a' a b' b m)) => MonadIO (StateP s p a' a b' b m) where
liftIO m = StateP $ \s -> liftIO $ liftM (\r -> (r, s)) m
instance (MFunctor (p a' a b' b)) => MFunctor (StateP s p a' a b' b) where
mapT nat = StateP . fmap (mapT nat) . unStateP
instance (Channel p) => Channel (StateP s p) where
idT a = StateP $ \_ -> idT a
(p1 >-> p2) a = StateP $ \s ->
((`unStateP` s) . p1 >-> (`unStateP` s) . p2) a
instance ProxyTrans (StateP s) where
liftP m = StateP $ \s -> liftM (\r -> (r, s)) m
runStateP :: s -> StateP s p a' a b' b m r -> p a' a b' b m (r, s)
runStateP s m = unStateP m s
runStateK :: s -> (q -> StateP s p a' a b' b m r) -> (q -> p a' a b' b m (r, s))
runStateK s = (runStateP s .)
evalStateP
:: (Monad (p a' a b' b m)) => s -> StateP s p a' a b' b m r -> p a' a b' b m r
evalStateP s = liftM fst . runStateP s
evalStateK
:: (Monad (p a' a b' b m))
=> s -> (q -> StateP s p a' a b' b m r) -> (q -> p a' a b' b m r)
evalStateK s = (evalStateP s .)
execStateP
:: (Monad (p a' a b' b m)) => s -> StateP s p a' a b' b m r -> p a' a b' b m s
execStateP s = liftM snd . runStateP s
execStateK
:: (Monad (p a' a b' b m))
=> s -> (q -> StateP s p a' a b' b m r) -> (q -> p a' a b' b m s)
execStateK s = (execStateP s .)
get :: (Monad (p a' a b' b m)) => StateP s p a' a b' b m s
get = StateP $ \s -> return (s, s)
put :: (Monad (p a' a b' b m)) => s -> StateP s p a' a b' b m ()
put s = StateP $ \_ -> return ((), s)
modify :: (Monad (p a' a b' b m)) => (s -> s) -> StateP s p a' a b' b m ()
modify f = StateP $ \s -> return ((), f s)
gets :: (Monad (p a' a b' b m)) => (s -> r) -> StateP s p a' a b' b m r
gets f = StateP $ \s -> return (f s, s)