Safe Haskell	None
Language	Haskell2010

Control.Effect.Error

Synopsis

data Error exc m k
- = Throw exc
- | Catch (m b) (exc -> m b) (b -> k)
throwError :: (Member (Error exc) sig, Carrier sig m) => exc -> m a
catchError :: (Member (Error exc) sig, Carrier sig m) => m a -> (exc -> m a) -> m a
runError :: (Carrier sig m, Effect sig, Monad m) => Eff (ErrorC exc m) a -> m (Either exc a)
newtype ErrorC e m a = ErrorC {
- runErrorC :: m (Either e a)
}

Documentation

data Error exc m k #

Constructors

Throw exc
Catch (m b) (exc -> m b) (b -> k)

Instances

Effect (Error exc) #
Instance details Defined in Control.Effect.Error Methods handle :: Functor f => f () -> (forall x. f (m x) -> n (f x)) -> Error exc m (m a) -> Error exc n (n (f a)) #
HFunctor (Error exc) #
Instance details Defined in Control.Effect.Error Methods fmap' :: (a -> b) -> Error exc m a -> Error exc m b # hmap :: (forall x. m x -> n x) -> Error exc m a -> Error exc n a #
Functor (Error exc m) #
Instance details Defined in Control.Effect.Error Methods fmap :: (a -> b) -> Error exc m a -> Error exc m b # (<$) :: a -> Error exc m b -> Error exc m a #
(Carrier sig m, Effect sig, Monad m) => Carrier (Error e :+: sig) (ErrorC e m) #
Instance details Defined in Control.Effect.Error Methods ret :: a -> ErrorC e m a # eff :: (Error e :+: sig) (ErrorC e m) (ErrorC e m a) -> ErrorC e m a #

throwError :: (Member (Error exc) sig, Carrier sig m) => exc -> m a #

Throw an error, escaping the current computation up to the nearest catchError (if any).

run (runError (throwError a)) == Left @Int @Int a

catchError :: (Member (Error exc) sig, Carrier sig m) => m a -> (exc -> m a) -> m a #

Run a computation which can throw errors with a handler to run on error.

Errors thrown by the handler will escape up to the nearest enclosing catchError (if any).

run (runError (pure a `catchError` pure)) == Right a

run (runError (throwError a `catchError` pure)) == Right @Int @Int a

run (runError (throwError a `catchError` (throwError @Int))) == Left @Int @Int a

runError :: (Carrier sig m, Effect sig, Monad m) => Eff (ErrorC exc m) a -> m (Either exc a) #

Run an Error effect, returning uncaught errors in Left and successful computations’ values in Right.

run (runError (pure a)) == Right @Int @Int a

newtype ErrorC e m a #

Constructors

ErrorC
Fields runErrorC :: m (Either e a)

Instances

(Carrier sig m, Effect sig, Monad m) => Carrier (Error e :+: sig) (ErrorC e m) #
Instance details Defined in Control.Effect.Error Methods ret :: a -> ErrorC e m a # eff :: (Error e :+: sig) (ErrorC e m) (ErrorC e m a) -> ErrorC e m a #