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Haskell Core Libraries (base package)ParentContentsIndex
Control.Monad.Error
Portability non-portable (reqruires multi-param type classes)
Stability experimental
Maintainer libraries@haskell.org
Description

The Error monad.

Rendered by Michael Weber mailto:michael.weber@post.rwth-aachen.de, inspired by the Haskell Monad Template Library from Andy Gill (http://www.cse.ogi.edu/~andy)

class Error a where
Methods
noMsg :: a
strMsg :: String -> a
Instances
Error [Char]
Error IOError
class (Monad m) => MonadError e m | m -> e where
Methods
throwError :: e -> m a
catchError :: m a -> (e -> m a) -> m a
Instances
MonadError IOError IO
(Error e) => MonadError e (Either e)
(Monad m, Error e) => MonadError e (ErrorT e m)
(MonadError e m) => MonadError e (ReaderT r m)
(Monoid w, MonadError e m) => MonadError e (WriterT w m)
(MonadError e m) => MonadError e (StateT s m)
(Monoid w, MonadError e m) => MonadError e (RWST r w s m)
(MonadError e m) => MonadError e (ListT m)
data ErrorT e m a
Constructors
ErrorT
runErrorT :: (m (Either e a))
Instances
(Monad m) => Functor (ErrorT e m)
(Monad m, Error e) => Monad (ErrorT e m)
(Monad m, Error e) => MonadPlus (ErrorT e m)
(MonadFix m, Error e) => MonadFix (ErrorT e m)
(Monad m, Error e) => MonadError e (ErrorT e m)
(Error e) => MonadTrans (ErrorT e)
(Error e, MonadIO m) => MonadIO (ErrorT e m)
(Error e, MonadReader r m) => MonadReader r (ErrorT e m)
(Error e, MonadWriter w m) => MonadWriter w (ErrorT e m)
(Error e, MonadState s m) => MonadState s (ErrorT e m)
(Error e, MonadCont m) => MonadCont (ErrorT e m)
runErrorT :: ErrorT e m a -> m (Either e a)
mapErrorT :: (m (Either e a) -> n (Either e' b)) -> ErrorT e m a -> ErrorT e' n b
module Control.Monad
module Control.Monad.Fix
module Control.Monad.Trans
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