Haskell Hierarchical Libraries (mtl package)ContentsIndex
Control.Monad.Error
Portability non-portable (multi-parameter 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/)

Synopsis
class Error a where
noMsg :: a
strMsg :: String -> a
class Monad m => MonadError e m | m -> e where
throwError :: e -> m a
catchError :: m a -> (e -> m a) -> m a
newtype ErrorT e m a = ErrorT {
runErrorT :: (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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