fused-effects-0.2.0.0: A fast, flexible, fused effect system.

Safe HaskellNone
LanguageHaskell2010

Control.Effect.Error

Synopsis

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, Monad m) => Carrier (Error e :+: sig) (ErrorC e m) Source # 
Instance details

Defined in Control.Effect.Error

Methods

ret :: a -> ErrorC e m a Source #

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 :: forall exc sig m a. (Carrier sig m, Effect sig, Monad m) => Eff (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

Instances
(Carrier sig m, Effect sig, Monad m) => Carrier (Error e :+: sig) (ErrorC e m) Source # 
Instance details

Defined in Control.Effect.Error

Methods

ret :: a -> ErrorC e m a Source #

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