Control.Monad.Trans.State.Plus

MonadPlus with left catch (MonadOr) for StateT.

The StatePlusT monad transformer

data StatePlusT s m a

StatePlusT behaves similar to StateT monad transformer

Instances

Monad m => MonadState s (StatePlusT s m)

MonadTrans (StatePlusT s)

Monad m => Monad (StatePlusT s m)

Functor m => Functor (StatePlusT s m)

(Monad m, Functor m) => Applicative (StatePlusT s m)

(Monad m, Functor m) => Alternative (StatePlusT s m)

Monad m => MonadPlus (StatePlusT s m)

MonadIO m => MonadIO (StatePlusT s m)

runStatePlusT :: Monad m => StatePlusT s m a -> s -> m (Maybe a, s)

Evaluate StatePlusT monad. In difference from runStateT it returns Nothing if mzero has been encountered. Just a otherwise.

execStatePlusT :: Monad m => StatePlusT s m a -> s -> m s

Execute StatePlusT monad returning resulting state

evalStatePlusT :: Monad m => StatePlusT s m a -> s -> m (Maybe a)

Evaluate StatePlusT monad returning resulting value. See above for the semantics.