Control.Monad.Backend

Defines the BackendT transformer, which is a variant of the StateT transformer, such that the state is within an MVar.

Documentation

newtype BackendT s m a

The BackendT transformer is a StateT, where the state is encapsulated into a MVar. The initialized MVar has to be non empty, otherwise every state change is blocking.

Constructors

BackendT (MVar s -> m (MVar s, a))

Instances

(Monad m, MonadIO m) => MonadState s (BackendT s m)

Monad m => Monad (BackendT s m)

Functor m => Functor (BackendT s m)

Monad m => Applicative (BackendT s m)

(Monad m, MonadIO m) => MonadIO (BackendT s m)

runBackendT :: BackendT s m a -> MVar s -> m (MVar s, a)

runBackendT unwraps the BackendT monad.