control-monad-failure-0.5.0: A class for monads which can fail with an error. Source code Contents Index

Control.Monad.Failure.Class

Description

Defines the class MonadFailure for monads which can fail.

Synopsis

class Monad m => MonadFailure e m where failure :: e -> m a class MonadFailure e m => WrapFailure e m where wrapFailure :: (forall eIn. Exception eIn => eIn -> e) -> m a -> m a failureString :: MonadFailure StringException m => String -> m a newtype StringException = StringException String

Documentation

class Monad m => MonadFailure e m where Source

Methods failure :: e -> m a Source Instances Exception e => MonadFailure e IO MonadFailure e [] MonadFailure e Maybe MonadFailure e m => MonadFailure e (ListT m) Error e => MonadFailure e (Either e) MonadFailure e m => MonadFailure e (StateT s m) (Monoid w, MonadFailure e m) => MonadFailure e (WriterT w m) MonadFailure e m => MonadFailure e (StateT s m) (Monoid w, MonadFailure e m) => MonadFailure e (WriterT w m) MonadFailure e m => MonadFailure e (ReaderT r m) (Error e, Monad m) => MonadFailure e (ErrorT e m) (Monoid w, MonadFailure e m) => MonadFailure e (RWST r w s m) (Monoid w, MonadFailure e m) => MonadFailure e (RWST r w s m)

class MonadFailure e m => WrapFailure e m where Source

Methods wrapFailure :: (forall eIn. Exception eIn => eIn -> e) -> m a -> m a Source Wrap the failure value, if any, with the given function. This is useful in particular when you want all the exceptions returned from a certain library to be of a certain type, even if they were generated by a different library. Instances Exception e => WrapFailure e IO WrapFailure e m => WrapFailure e (ListT m) WrapFailure e m => WrapFailure e (StateT s m) WrapFailure e m => WrapFailure e (StateT s m) (WrapFailure e m, Monoid w) => WrapFailure e (WriterT w m) WrapFailure e m => WrapFailure e (ReaderT r m) (WrapFailure e m, Monoid w) => WrapFailure e (RWST r w s m) (WrapFailure e m, Monoid w) => WrapFailure e (RWST r w s m)

failureString :: MonadFailure StringException m => String -> m a Source

Call failure with a String.

newtype StringException Source

Constructors StringException String Instances Show StringException Typeable StringException Exception StringException

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