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Error

Synopsis

class MonadPlus m => MonadError' e m where throwError' :: e -> m a catchError' :: m a -> (e -> m a) -> m a maybe2Error :: MonadError' e m => e -> Maybe a -> m a

Documentation

class MonadPlus m => MonadError' e m where

Same as MonadError, but without the functional dependency m -> e. This allows to have monads handling multiple error types, for instance using dynamic exceptions in MonadException. Methods throwError' :: e -> m a catchError' :: m a -> (e -> m a) -> m a Instances (MonadPlus m, MonadException m, Typeable e) => MonadError' e m Error e => MonadError' e (Either e) (Error e, Monad m) => MonadError' e (ErrorT e m) MonadError' e m => MonadError' e (StateT s m)

maybe2Error :: MonadError' e m => e -> Maybe a -> m a

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