Safe Haskell	Safe
Language	Haskell2010

Control.Eff.Exception

Description

Exception-producing and exception-handling effects

Synopsis

newtype Exc e (v :: k) = Exc e
exc :: Monad m => e -> m (Either e a)
withException :: Monad m => a -> m (Either e a)
type Fail = Exc () :: k -> Type
throwError :: forall e (r :: [Type -> Type]) a. Member (Exc e :: Type -> Type) r => e -> Eff r a
throwError_ :: forall e (r :: [Type -> Type]). Member (Exc e :: Type -> Type) r => e -> Eff r ()
die :: forall (r :: [Type -> Type]) a. Member (Fail :: Type -> Type) r => Eff r a
runError :: forall e (r :: [Type -> Type]) a. Eff ((Exc e :: Type -> Type) ': r) a -> Eff r (Either e a)
runFail :: forall (r :: [Type -> Type]) a. Eff ((Fail :: Type -> Type) ': r) a -> Eff r (Maybe a)
catchError :: forall e (r :: [Type -> Type]) a. Member (Exc e :: Type -> Type) r => Eff r a -> (e -> Eff r a) -> Eff r a
onFail :: forall (r :: [Type -> Type]) a. Eff ((Fail :: Type -> Type) ': r) a -> Eff r a -> Eff r a
rethrowError :: forall e' (r :: [Type -> Type]) e a. Member (Exc e' :: Type -> Type) r => (e -> e') -> Eff ((Exc e :: Type -> Type) ': r) a -> Eff r a
liftEither :: forall e (r :: [Type -> Type]) a. Member (Exc e :: Type -> Type) r => Either e a -> Eff r a
liftEitherM :: forall e (r :: [Type -> Type]) m a. (Member (Exc e :: Type -> Type) r, Lifted m r) => m (Either e a) -> Eff r a
liftMaybe :: forall (r :: [Type -> Type]) a. Member (Fail :: Type -> Type) r => Maybe a -> Eff r a
liftMaybeM :: forall (r :: [Type -> Type]) m a. (Member (Fail :: Type -> Type) r, Lifted m r) => m (Maybe a) -> Eff r a
ignoreFail :: forall (r :: [Type -> Type]) a. Eff ((Fail :: Type -> Type) ': r) a -> Eff r ()

Documentation

newtype Exc e (v :: k) Source #

Exceptions

exceptions of the type e; no resumption

Constructors

Exc e

Instances

Instances details

(MonadBase m m, LiftedBase m r) => MonadBaseControl m (Eff ((Exc e :: Type -> Type) ': r)) Source #
Instance details Defined in Control.Eff.Exception Methods liftBaseWith :: (RunInBase (Eff ((Exc e :: Type -> Type) ': r)) m -> m a) -> Eff ((Exc e :: Type -> Type) ': r) a # restoreM :: StM (Eff ((Exc e :: Type -> Type) ': r)) a -> Eff ((Exc e :: Type -> Type) ': r) a #
Monad m => Handle (Exc e :: Type -> Type) r a (m (Either e a)) Source #	Given a callback, and an `Exc` request, respond to it.
Instance details Defined in Control.Eff.Exception Methods handle :: (Eff r a -> m (Either e a)) -> Arrs r v a -> Exc e v -> m (Either e a) Source # handle_relay :: forall (r' :: [Type -> Type]). (r ~ ((Exc e :: Type -> Type) ': r'), Relay (m (Either e a)) r') => (a -> m (Either e a)) -> (Eff r a -> m (Either e a)) -> Eff r a -> m (Either e a) Source # respond_relay :: (a -> m (Either e a)) -> (Eff r a -> m (Either e a)) -> Eff r a -> m (Either e a) Source #
type StM (Eff ((Exc e :: Type -> Type) ': r)) a Source #
Instance details Defined in Control.Eff.Exception type StM (Eff ((Exc e :: Type -> Type) ': r)) a = StM (Eff r) (Either e a)

exc :: Monad m => e -> m (Either e a) Source #

Throw an error

withException :: Monad m => a -> m (Either e a) Source #

Embed a pure value

type Fail = Exc () :: k -> Type Source #

throwError :: forall e (r :: [Type -> Type]) a. Member (Exc e :: Type -> Type) r => e -> Eff r a Source #

Throw an exception in an effectful computation. The type is inferred.

throwError_ :: forall e (r :: [Type -> Type]). Member (Exc e :: Type -> Type) r => e -> Eff r () Source #

Throw an exception in an effectful computation. The type is unit, which suppresses the ghc-mod warning "A do-notation statement discarded a result of type"

die :: forall (r :: [Type -> Type]) a. Member (Fail :: Type -> Type) r => Eff r a Source #

Makes an effect fail, preventing future effects from happening.

runError :: forall e (r :: [Type -> Type]) a. Eff ((Exc e :: Type -> Type) ': r) a -> Eff r (Either e a) Source #

Run a computation that might produce an exception.

runFail :: forall (r :: [Type -> Type]) a. Eff ((Fail :: Type -> Type) ': r) a -> Eff r (Maybe a) Source #

Runs a failable effect, such that failed computation return Nothing, and Just the return value on success.

catchError :: forall e (r :: [Type -> Type]) a. Member (Exc e :: Type -> Type) r => Eff r a -> (e -> Eff r a) -> Eff r a Source #

Run a computation that might produce exceptions, and give it a way to deal with the exceptions that come up. The handler is allowed to rethrow the exception

onFail Source #

Arguments

:: forall (r :: [Type -> Type]) a. Eff ((Fail :: Type -> Type) ': r) a	The fallible computation.
-> Eff r a	The computation to run on failure.
-> Eff r a

Add a default value (i.e. failure handler) to a fallible computation. This hides the fact that a failure happened.

rethrowError :: forall e' (r :: [Type -> Type]) e a. Member (Exc e' :: Type -> Type) r => (e -> e') -> Eff ((Exc e :: Type -> Type) ': r) a -> Eff r a Source #

Run a computation until it produces an exception, and convert and throw that exception in a new context.

liftEither :: forall e (r :: [Type -> Type]) a. Member (Exc e :: Type -> Type) r => Either e a -> Eff r a Source #

Treat Lefts as exceptions and Rights as return values.

liftEitherM :: forall e (r :: [Type -> Type]) m a. (Member (Exc e :: Type -> Type) r, Lifted m r) => m (Either e a) -> Eff r a Source #

liftEither in a lifted Monad

liftMaybe :: forall (r :: [Type -> Type]) a. Member (Fail :: Type -> Type) r => Maybe a -> Eff r a Source #

Lift a maybe into the Fail effect, causing failure if it's Nothing.

liftMaybeM :: forall (r :: [Type -> Type]) m a. (Member (Fail :: Type -> Type) r, Lifted m r) => m (Maybe a) -> Eff r a Source #

liftMaybe in a lifted Monad

ignoreFail :: forall (r :: [Type -> Type]) a. Eff ((Fail :: Type -> Type) ': r) a -> Eff r () Source #

Ignores a failure event. Since the event can fail, you cannot inspect its return type, because it has none on failure. To inspect it, use runFail.