Control.Monad.Freer.Exception

Composable handler for Exception effects. Communicates success/failure via an Either type.

Using http://okmij.org/ftp/Haskell/extensible/Eff1.hs as a starting point.

Documentation

newtype Exc e v

Exceptions of the type e; no resumption

Constructors

Exc e

throwError :: Member (Exc e) r => e -> Eff r a

Throws an error carrying information of type e

runError :: Eff (Exc e ': r) a -> Eff r (Either e a)

Handler for exception effects If there are no exceptions thrown, returns Right If exceptions are thrown and not handled, returns Left, interrupting the execution of any other effect handlers.

catchError :: Member (Exc e) r => Eff r a -> (e -> Eff r a) -> Eff r a

A catcher for Exceptions. Handlers are allowed to rethrow exceptions.