Control.Effect.Error

Documentation

data Error exc m k

Constructors

Throw exc

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

Instances

Effect (Error exc)

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)

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)

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)

Defined in Control.Effect.Error

Methods

eff :: (Error e :+: sig) (ErrorC e m) (ErrorC e m a) -> ErrorC e m a

ret :: 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). 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)

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

MonadTrans (ErrorC e)

Defined in Control.Effect.Error

Methods

lift :: Monad m => m a -> ErrorC e m a

Monad m => Monad (ErrorC e m)

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)

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)

Defined in Control.Effect.Error

Methods

fail :: String -> ErrorC e m a

Applicative m => Applicative (ErrorC e m)

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)

Defined in Control.Effect.Error

Methods

liftIO :: IO a -> ErrorC e m a

Alternative m => Alternative (ErrorC e m)

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)

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)

Defined in Control.Effect.Error

Methods

eff :: (Error e :+: sig) (ErrorC e m) (ErrorC e m a) -> ErrorC e m a

ret :: a -> ErrorC e m a