monads-tf-0.3.0.1: Monad classes, using type families
Copyright(c) Andy Gill 2001
(c) Oregon Graduate Institute of Science and Technology 2001
LicenseBSD-style (see the file LICENSE)
Maintainerross@soi.city.ac.uk
Stabilityexperimental
Portabilityportable
Safe HaskellNone
LanguageGHC2021

Control.Monad.Trans

Description

Classes for monad transformers.

A monad transformer makes new monad out of an existing monad, such that computations of the old monad may be embedded in the new one. To construct a monad with a desired set of features, one typically starts with a base monad, such as Identity, [] or IO, and applies a sequence of monad transformers.

Most monad transformer modules include the special case of applying the transformer to Identity. For example, State s is an abbreviation for StateT s Identity.

Each monad transformer also comes with an operation runXXX to unwrap the transformer, exposing a computation of the inner monad.

Documentation

class (forall (m :: Type -> Type). Monad m => Monad (t m)) => MonadTrans (t :: (Type -> Type) -> Type -> Type) where #

Methods

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

Instances

Instances details
MonadTrans MaybeT 
Instance details

Defined in Control.Monad.Trans.Maybe

Methods

lift :: Monad m => m a -> MaybeT m a #

Monoid w => MonadTrans (AccumT w) 
Instance details

Defined in Control.Monad.Trans.Accum

Methods

lift :: Monad m => m a -> AccumT w m a #

MonadTrans (ExceptT e) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

lift :: Monad m => m a -> ExceptT e m a #

MonadTrans (IdentityT :: (Type -> Type) -> Type -> Type) 
Instance details

Defined in Control.Monad.Trans.Identity

Methods

lift :: Monad m => m a -> IdentityT m a #

MonadTrans (ReaderT r) 
Instance details

Defined in Control.Monad.Trans.Reader

Methods

lift :: Monad m => m a -> ReaderT r m a #

MonadTrans (SelectT r) 
Instance details

Defined in Control.Monad.Trans.Select

Methods

lift :: Monad m => m a -> SelectT r m a #

MonadTrans (StateT s) 
Instance details

Defined in Control.Monad.Trans.State.Lazy

Methods

lift :: Monad m => m a -> StateT s m a #

MonadTrans (StateT s) 
Instance details

Defined in Control.Monad.Trans.State.Strict

Methods

lift :: Monad m => m a -> StateT s m a #

MonadTrans (WriterT w) 
Instance details

Defined in Control.Monad.Trans.Writer.CPS

Methods

lift :: Monad m => m a -> WriterT w m a #

Monoid w => MonadTrans (WriterT w) 
Instance details

Defined in Control.Monad.Trans.Writer.Lazy

Methods

lift :: Monad m => m a -> WriterT w m a #

Monoid w => MonadTrans (WriterT w) 
Instance details

Defined in Control.Monad.Trans.Writer.Strict

Methods

lift :: Monad m => m a -> WriterT w m a #

MonadTrans (ContT r) 
Instance details

Defined in Control.Monad.Trans.Cont

Methods

lift :: Monad m => m a -> ContT r m a #

MonadTrans (RWST r w s) 
Instance details

Defined in Control.Monad.Trans.RWS.CPS

Methods

lift :: Monad m => m a -> RWST r w s m a #

Monoid w => MonadTrans (RWST r w s) 
Instance details

Defined in Control.Monad.Trans.RWS.Lazy

Methods

lift :: Monad m => m a -> RWST r w s m a #

Monoid w => MonadTrans (RWST r w s) 
Instance details

Defined in Control.Monad.Trans.RWS.Strict

Methods

lift :: Monad m => m a -> RWST r w s m a #

class Monad m => MonadIO (m :: Type -> Type) where #

Methods

liftIO :: IO a -> m a #

Instances

Instances details
MonadIO IO 
Instance details

Defined in Control.Monad.IO.Class

Methods

liftIO :: IO a -> IO a #

MonadIO m => MonadIO (MaybeT m) 
Instance details

Defined in Control.Monad.Trans.Maybe

Methods

liftIO :: IO a -> MaybeT m a #

(Monoid w, Functor m, MonadIO m) => MonadIO (AccumT w m) 
Instance details

Defined in Control.Monad.Trans.Accum

Methods

liftIO :: IO a -> AccumT w m a #

MonadIO m => MonadIO (ExceptT e m) 
Instance details

Defined in Control.Monad.Trans.Except

Methods

liftIO :: IO a -> ExceptT e m a #

MonadIO m => MonadIO (IdentityT m) 
Instance details

Defined in Control.Monad.Trans.Identity

Methods

liftIO :: IO a -> IdentityT m a #

MonadIO m => MonadIO (ReaderT r m) 
Instance details

Defined in Control.Monad.Trans.Reader

Methods

liftIO :: IO a -> ReaderT r m a #

MonadIO m => MonadIO (SelectT r m) 
Instance details

Defined in Control.Monad.Trans.Select

Methods

liftIO :: IO a -> SelectT r m a #

MonadIO m => MonadIO (StateT s m) 
Instance details

Defined in Control.Monad.Trans.State.Lazy

Methods

liftIO :: IO a -> StateT s m a #

MonadIO m => MonadIO (StateT s m) 
Instance details

Defined in Control.Monad.Trans.State.Strict

Methods

liftIO :: IO a -> StateT s m a #

MonadIO m => MonadIO (WriterT w m) 
Instance details

Defined in Control.Monad.Trans.Writer.CPS

Methods

liftIO :: IO a -> WriterT w m a #

(Monoid w, MonadIO m) => MonadIO (WriterT w m) 
Instance details

Defined in Control.Monad.Trans.Writer.Lazy

Methods

liftIO :: IO a -> WriterT w m a #

(Monoid w, MonadIO m) => MonadIO (WriterT w m) 
Instance details

Defined in Control.Monad.Trans.Writer.Strict

Methods

liftIO :: IO a -> WriterT w m a #

MonadIO m => MonadIO (ContT r m) 
Instance details

Defined in Control.Monad.Trans.Cont

Methods

liftIO :: IO a -> ContT r m a #

MonadIO m => MonadIO (RWST r w s m) 
Instance details

Defined in Control.Monad.Trans.RWS.CPS

Methods

liftIO :: IO a -> RWST r w s m a #

(Monoid w, MonadIO m) => MonadIO (RWST r w s m) 
Instance details

Defined in Control.Monad.Trans.RWS.Lazy

Methods

liftIO :: IO a -> RWST r w s m a #

(Monoid w, MonadIO m) => MonadIO (RWST r w s m) 
Instance details

Defined in Control.Monad.Trans.RWS.Strict

Methods

liftIO :: IO a -> RWST r w s m a #