Control.Monad.Trans.Ether.Except

See Control.Monad.Trans.Except.

The Except monad

type Except tag e = ExceptT tag e Identity

The parameterizable exception monad.

Computations are either exceptions or normal values.

The return function returns a normal value, while >>= exits on the first exception.

except :: Monad m => proxy tag -> Either e a -> ExceptT tag e m a

Constructor for computations in the exception monad (the inverse of runExcept).

runExcept :: proxy tag -> Except tag e a -> Either e a

Runs an Except and returns either an exception or a normal value.

The ExceptT monad transformer

data ExceptT tag e m a

The exception monad transformer.

The return function returns a normal value, while >>= exits on the first exception.

Instances

MonadReader tag r m => MonadReader tag r (ExceptT tag' e m)

MonadState tag s m => MonadState tag s (ExceptT tag' e m)

MonadExcept tag e m => MonadExcept tag e (ExceptT tag' e' m)

Monad m => MonadExcept tag e (ExceptT tag e m)

MonadWriter tag w m => MonadWriter tag w (ExceptT tag' e m)

MonadError e' m => MonadError e' (ExceptT tag e m)

MonadReader r m => MonadReader r (ExceptT tag e m)

MonadState s m => MonadState s (ExceptT tag e m)

MonadWriter w m => MonadWriter w (ExceptT tag e m)

MonadTrans (ExceptT tag e)

(Monad m, Functor m, Monoid e) => Alternative (ExceptT tag e m)

Monad m => Monad (ExceptT tag e m)

Functor m => Functor (ExceptT tag e m)

MonadFix m => MonadFix (ExceptT tag e m)

(Monad m, Monoid e) => MonadPlus (ExceptT tag e m)

(Monad m, Functor m) => Applicative (ExceptT tag e m)

MonadIO m => MonadIO (ExceptT tag e m)

MonadCont m => MonadCont (ExceptT tag e m)

Taggable (ExceptT tag e m)

Tagged (ExceptT tag e m) tag

Generic (ExceptT tag e m a)

Newtype (ExceptT tag e m a)

type Untagged (ExceptT tag e m) = ExceptT e m

type Tag (ExceptT tag e m) = Just * tag

type Inner (ExceptT tag e m) = Just (* -> *) m

type Rep (ExceptT tag e m a)

type O (ExceptT tag e m a) = GO (Rep (ExceptT tag e m a))

exceptT :: proxy tag -> m (Either e a) -> ExceptT tag e m a

Constructor for computations in the exception monad transformer.

runExceptT :: proxy tag -> ExceptT tag e m a -> m (Either e a)

Runs an ExceptT and returns either an exception or a normal value.

mapExceptT :: proxy tag -> (m (Either e a) -> n (Either e' b)) -> ExceptT tag e m a -> ExceptT tag e' n b

Transforms the computation inside an ExceptT.

• runExceptT tag (mapExceptT tag f m) = f (runExceptT tag m)

Exception operations

throw :: Monad m => proxy tag -> e -> ExceptT tag e m a

Is used within a monadic computation to begin exception processing.

catch :: Monad m => proxy tag -> ExceptT tag e m a -> (e -> ExceptT tag e m a) -> ExceptT tag e m a

A handler function to handle previous exceptions and return to normal execution.

Lifting other operations

liftCallCC :: proxy tag -> CallCC m (Either e a) (Either e b) -> CallCC (ExceptT tag e m) a b

Lift a callCC operation to the new monad.

liftListen :: Monad m => proxy tag -> Listen w m (Either e a) -> Listen w (ExceptT tag e m) a

Lift a listen operation to the new monad.

liftPass :: Monad m => proxy tag -> Pass w m (Either e a) -> Pass w (ExceptT tag e m) a

Lift a pass operation to the new monad.

liftCatch :: proxy tag -> Catch e m (Either e' a) -> Catch e (ExceptT tag e' m) a

Lift a catchE operation to the new monad.