Copyright	(c) Andy Gill 2001 (c) Oregon Graduate Institute of Science and Technology 2001
License	BSD-style (see the file libraries/base/LICENSE)
Maintainer	libraries@haskell.org
Stability	experimental
Portability	portable
Safe Haskell	Safe
Language	Haskell2010

Control.Monad.Trans

Description

The MonadTrans class.

Inspired by the paper /Functional Programming with Overloading and Higher-Order Polymorphism/, Mark P Jones (http://www.cse.ogi.edu/~mpj/) Advanced School of Functional Programming, 1995.

Synopsis

Documentation

class MonadTrans (t :: (* -> *) -> * -> *) where #

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

```
lift . return = return
```
```
lift (m >>= f) = lift m >>= (lift . f)
```

Minimal complete definition

lift

Methods

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

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

Instances

Monoid w => MonadTrans (WriterT w)
Methods lift :: Monad m => m a -> WriterT w m a #
Monoid w => MonadTrans (WriterT w)
Methods lift :: Monad m => m a -> WriterT w m a #
MonadTrans (StateT s)
Methods lift :: Monad m => m a -> StateT s m a #
MonadTrans (StateT s)
Methods lift :: Monad m => m a -> StateT s m a #
MonadTrans (IdentityT *)
Methods lift :: Monad m => m a -> IdentityT * m a #
MonadTrans (ExceptT e)
Methods lift :: Monad m => m a -> ExceptT e m a #
MonadTrans (ReaderT * r)
Methods lift :: Monad m => m a -> ReaderT * r m a #
MonadTrans (ContT * r)
Methods lift :: Monad m => m a -> ContT * r m a #
Monoid w => MonadTrans (RWST r w s)
Methods lift :: Monad m => m a -> RWST r w s m a #
Monoid w => MonadTrans (RWST r w s)
Methods lift :: Monad m => m a -> RWST r w s m a #

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

Monads in which IO computations may be embedded. Any monad built by applying a sequence of monad transformers to the IO monad will be an instance of this class.

Instances should satisfy the following laws, which state that liftIO is a transformer of monads:

```
liftIO . return = return
```

liftIO (m >>= f) = liftIO m >>= (liftIO . f)

Minimal complete definition

liftIO

Methods

liftIO :: IO a -> m a #

Lift a computation from the IO monad.

Instances

MonadIO IO	Since: 4.9.0.0
Methods liftIO :: IO a -> IO a #
(Monoid w, MonadIO m) => MonadIO (WriterT w m)
Methods liftIO :: IO a -> WriterT w m a #
(Monoid w, MonadIO m) => MonadIO (WriterT w m)
Methods liftIO :: IO a -> WriterT w m a #
MonadIO m => MonadIO (StateT s m)
Methods liftIO :: IO a -> StateT s m a #
MonadIO m => MonadIO (StateT s m)
Methods liftIO :: IO a -> StateT s m a #
MonadIO m => MonadIO (IdentityT * m)
Methods liftIO :: IO a -> IdentityT * m a #
MonadIO m => MonadIO (ExceptT e m)
Methods liftIO :: IO a -> ExceptT e m a #
MonadIO m => MonadIO (ReaderT * r m)
Methods liftIO :: IO a -> ReaderT * r m a #
MonadIO m => MonadIO (ContT * r m)
Methods liftIO :: IO a -> ContT * r m a #
(Monoid w, MonadIO m) => MonadIO (RWST r w s m)
Methods liftIO :: IO a -> RWST r w s m a #
(Monoid w, MonadIO m) => MonadIO (RWST r w s m)
Methods liftIO :: IO a -> RWST r w s m a #