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 :: 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 Source #

Constructors

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

Instances

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

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

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 Source #

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). Note that this effect does not handle errors thrown from impure contexts such as IO, nor will it handle exceptions thrown from pure code. If you need to handle IO-based errors, consider if Resource fits your use case; if not, use liftIO with try or use Catch from outside the effect invocation.

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 :: ErrorC exc m a -> m (Either exc a) Source #

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 Source #

Constructors

ErrorC
Fields runErrorC :: m (Either e a)

Instances

MonadTrans (ErrorC e) Source #
Instance details Defined in Control.Effect.Error Methods lift :: Monad m => m a -> ErrorC e m a #
Monad m => Monad (ErrorC e m) Source #
Instance details Defined in Control.Effect.Error Methods (>>=) :: ErrorC e m a -> (a -> ErrorC e m b) -> ErrorC e m b # (>>) :: ErrorC e m a -> ErrorC e m b -> ErrorC e m b # return :: a -> ErrorC e m a # fail :: String -> ErrorC e m a #
Functor m => Functor (ErrorC e m) Source #
Instance details Defined in Control.Effect.Error Methods fmap :: (a -> b) -> ErrorC e m a -> ErrorC e m b # (<$) :: a -> ErrorC e m b -> ErrorC e m a #
MonadFail m => MonadFail (ErrorC e m) Source #
Instance details Defined in Control.Effect.Error Methods fail :: String -> ErrorC e m a #
Applicative m => Applicative (ErrorC e m) Source #
Instance details Defined in Control.Effect.Error Methods pure :: a -> ErrorC e m a # (<>) :: ErrorC e m (a -> b) -> ErrorC e m a -> ErrorC e m b # liftA2 :: (a -> b -> c) -> ErrorC e m a -> ErrorC e m b -> ErrorC e m c # (>) :: ErrorC e m a -> ErrorC e m b -> ErrorC e m b # (<*) :: ErrorC e m a -> ErrorC e m b -> ErrorC e m a #
MonadIO m => MonadIO (ErrorC e m) Source #
Instance details Defined in Control.Effect.Error Methods liftIO :: IO a -> ErrorC e m a #
Alternative m => Alternative (ErrorC e m) Source #
Instance details Defined in Control.Effect.Error Methods empty :: ErrorC e m a # (<\|>) :: ErrorC e m a -> ErrorC e m a -> ErrorC e m a # some :: ErrorC e m a -> ErrorC e m [a] # many :: ErrorC e m a -> ErrorC e m [a] #
(Alternative m, Monad m) => MonadPlus (ErrorC e m) Source #
Instance details Defined in Control.Effect.Error Methods mzero :: ErrorC e m a # mplus :: ErrorC e m a -> ErrorC e m a -> ErrorC e m a #
(Carrier sig m, Effect sig) => Carrier (Error e :+: sig) (ErrorC e m) Source #
Instance details Defined in Control.Effect.Error Methods eff :: (Error e :+: sig) (ErrorC e m) (ErrorC e m a) -> ErrorC e m a Source #