Control.Monad.Trans.Unlift

See overview in the README.md

Trans

class (MonadTransControl t, Forall (Identical t)) => MonadTransUnlift t

A monad transformer which can be unlifted, obeying the monad morphism laws.

Since 0.1.0

Instances

(MonadTransControl t, Forall (Identical t)) => MonadTransUnlift t

newtype Unlift t

A function which can move an action down the monad transformer stack, by providing any necessary environment to the action.

Note that, if ImpredicativeTypes worked reliably, this type wouldn't be necessary, and askUnlift would simply include a more generalized type.

Since 0.1.0

Constructors

Unlift

Fields

unlift :: forall a n. Monad n => t n a -> n a

askUnlift :: forall t m. (MonadTransUnlift t, Monad m) => t m (Unlift t)

Get the Unlift action for the current transformer layer.

Since 0.1.0

askRun :: (MonadTransUnlift t, Monad (t m), Monad m) => t m (t m a -> m a)

A simplified version of askUnlift which addresses the common case where polymorphism isn't necessary.

Since 0.1.0

Base

class (MonadBaseControl b m, Forall (IdenticalBase m)) => MonadBaseUnlift b m | m -> b

A monad transformer stack which can be unlifted, obeying the monad morphism laws.

Since 0.1.0

Instances

(MonadBaseControl b m, Forall (IdenticalBase m)) => MonadBaseUnlift b m

newtype UnliftBase b m

Similar to Unlift, but instead of moving one layer down the stack, moves the action to the base monad.

Since 0.1.0

Constructors

UnliftBase

Fields

unliftBase :: forall a. m a -> b a

askUnliftBase :: forall b m. MonadBaseUnlift b m => m (UnliftBase b m)

Get the UnliftBase action for the current transformer stack.

Since 0.1.0

askRunBase :: MonadBaseUnlift b m => m (m a -> b a)

A simplified version of askUnliftBase which addresses the common case where polymorphism isn't necessary.

Since 0.1.0

Reexports

class MonadTrans t where

The class of monad transformers. Instances should satisfy the following laws, which state that lift is a transformer of monads:

• lift . return = return

• lift (m >>= f) = lift m >>= (lift . f)

Methods

lift :: Monad m => m a -> t m a

Lift a computation from the argument monad to the constructed monad.

Instances

MonadTrans MaybeT

MonadTrans ListT

MonadTrans IdentityT

Monoid w => MonadTrans (WriterT w)

Monoid w => MonadTrans (WriterT w)

MonadTrans (StateT s)

MonadTrans (StateT s)

MonadTrans (ReaderT r)

Error e => MonadTrans (ErrorT e)

MonadTrans (ContT r)

MonadTrans (ExceptT e)

MonadTrans (StateRefT ref s)

MonadTrans (WriterRefT ref w)

Monoid w => MonadTrans (RWST r w s)

Monoid w => MonadTrans (RWST r w s)

MonadTrans (RWSRefT refw refs r w s)

class (Applicative b, Applicative m, Monad b, Monad m) => MonadBase b m | m -> b where

Methods

liftBase :: b α -> m α

Instances

MonadBase [] []

MonadBase IO IO

MonadBase STM STM

MonadBase Maybe Maybe

MonadBase Identity Identity

MonadBase b m => MonadBase b (MaybeT m)

MonadBase b m => MonadBase b (ListT m)

MonadBase b m => MonadBase b (IdentityT m)

(Monoid w, MonadBase b m) => MonadBase b (WriterT w m)

(Monoid w, MonadBase b m) => MonadBase b (WriterT w m)

MonadBase b m => MonadBase b (StateT s m)

MonadBase b m => MonadBase b (StateT s m)

MonadBase b m => MonadBase b (ReaderT r m)

MonadBase b m => MonadBase b (ExceptT e m)

(Error e, MonadBase b m) => MonadBase b (ErrorT e m)

MonadBase b m => MonadBase b (ContT r m)

MonadBase b m => MonadBase b (StateRefT ref s m)

MonadBase b m => MonadBase b (WriterRefT ref w m)

(Monoid w, MonadBase b m) => MonadBase b (RWST r w s m)

(Monoid w, MonadBase b m) => MonadBase b (RWST r w s m)

MonadBase b m => MonadBase b (RWSRefT refw refs r w s m)

MonadBase ((->) r) ((->) r)

MonadBase (Either e) (Either e)

MonadBase (ST s) (ST s)

MonadBase (ST s) (ST s)

class MonadTrans t => MonadTransControl t where

Associated Types

type StT t a :: *

Methods

liftWith :: Monad m => (Run t -> m a) -> t m a

restoreT :: Monad m => m (StT t a) -> t m a

Instances

MonadTransControl MaybeT

MonadTransControl ListT

MonadTransControl IdentityT

Monoid w => MonadTransControl (WriterT w)

Monoid w => MonadTransControl (WriterT w)

MonadTransControl (StateT s)

MonadTransControl (StateT s)

MonadTransControl (ReaderT r)

Error e => MonadTransControl (ErrorT e)

MonadTransControl (ExceptT e)

MonadTransControl (StateRefT ref s)

MonadTransControl (WriterRefT ref w)

Monoid w => MonadTransControl (RWST r w s)

Monoid w => MonadTransControl (RWST r w s)

MonadTransControl (RWSRefT refw refs r w s)

class MonadBase b m => MonadBaseControl b m | m -> b where

Associated Types

type StM m a :: *

Methods

liftBaseWith :: (RunInBase m b -> b a) -> m a

restoreM :: StM m a -> m a

Instances

MonadBaseControl [] []

MonadBaseControl IO IO

MonadBaseControl STM STM

MonadBaseControl Maybe Maybe

MonadBaseControl Identity Identity

MonadBaseControl b m => MonadBaseControl b (MaybeT m)

MonadBaseControl b m => MonadBaseControl b (ListT m)

MonadBaseControl b m => MonadBaseControl b (IdentityT m)

(Monoid w, MonadBaseControl b m) => MonadBaseControl b (WriterT w m)

(Monoid w, MonadBaseControl b m) => MonadBaseControl b (WriterT w m)

MonadBaseControl b m => MonadBaseControl b (StateT s m)

MonadBaseControl b m => MonadBaseControl b (StateT s m)

MonadBaseControl b m => MonadBaseControl b (ReaderT r m)

MonadBaseControl b m => MonadBaseControl b (ExceptT e m)

(Error e, MonadBaseControl b m) => MonadBaseControl b (ErrorT e m)

MonadBaseControl b m => MonadBaseControl b (StateRefT ref s m)

MonadBaseControl b m => MonadBaseControl b (WriterRefT ref w m)

(Monoid w, MonadBaseControl b m) => MonadBaseControl b (RWST r w s m)

(Monoid w, MonadBaseControl b m) => MonadBaseControl b (RWST r w s m)

MonadBaseControl b m => MonadBaseControl b (RWSRefT refw refs r w s m)

MonadBaseControl ((->) r) ((->) r)

MonadBaseControl (Either e) (Either e)

MonadBaseControl (ST s) (ST s)

MonadBaseControl (ST s) (ST s)