Control.Monad.Trans.BackwardState

Backward state monad and transformer, in which m >> n passes the incoming state to n, then passes n's resulting state to m. This can only work lazily.

Documentation

type BackwardState s = BackwardStateT s Identity

runBackwardState :: BackwardState s a -> s -> (a, s)

evalBackwardState :: BackwardState s a -> s -> a

execBackwardState :: BackwardState s a -> s -> s

newtype BackwardStateT s m a

Constructors

BackwardStateT

Fields

runBackwardStateT :: s -> m (a, s)

Instances

MonadTrans (BackwardStateT s)

MonadFix m => Monad (BackwardStateT s m)

Functor m => Functor (BackwardStateT s m)

(Monad (BackwardStateT s m), MonadFix m) => MonadFix (BackwardStateT s m)

(Monad (BackwardStateT s m), MonadFix m, MonadPlus m) => MonadPlus (BackwardStateT s m)

(Functor (BackwardStateT s m), Functor m, MonadFix m) => Applicative (BackwardStateT s m)

(Applicative (BackwardStateT s m), Functor m, MonadFix m, MonadPlus m) => Alternative (BackwardStateT s m)

(Monad (BackwardStateT s m), MonadFix m, MonadIO m) => MonadIO (BackwardStateT s m)

evalBackwardStateT :: Functor m => BackwardStateT s m a -> s -> m a

execBackwardStateT :: Functor m => BackwardStateT s m a -> s -> m s

get :: Monad m => BackwardStateT s m s

put :: Monad m => s -> BackwardStateT s m ()

modify :: Monad m => (s -> s) -> BackwardStateT s m ()