Safe Haskell | Trustworthy |
---|---|

Language | Haskell98 |

Exception-producing and exception-handling effects

- newtype Exc e v = Exc e
- type Fail = Exc ()
- throwExc :: (Typeable e, Member (Exc e) r) => e -> Eff r a
- die :: Member Fail r => Eff r a
- runExc :: Typeable e => Eff (Exc e :> r) a -> Eff r (Either e a)
- runFail :: Eff (Fail :> r) a -> Eff r (Maybe a)
- catchExc :: (Typeable e, Member (Exc e) r) => Eff r a -> (e -> Eff r a) -> Eff r a
- onFail :: Eff (Fail :> r) a -> Eff r a -> Eff r a
- rethrowExc :: (Typeable e, Typeable e', Member (Exc e') r) => (e -> e') -> Eff (Exc e :> r) a -> Eff r a
- liftEither :: (Typeable e, Member (Exc e) r) => Either e a -> Eff r a
- liftEitherM :: (Typeable m, Typeable e, Member (Exc e) r, SetMember Lift (Lift m) r) => m (Either e a) -> Eff r a
- liftMaybe :: Member Fail r => Maybe a -> Eff r a
- ignoreFail :: Eff (Fail :> r) a -> Eff r ()

# Documentation

These are exceptions of the type e. This is akin to the error monad.

Exc e |

throwExc :: (Typeable e, Member (Exc e) r) => e -> Eff r a Source

Throw an exception in an effectful computation.

die :: Member Fail r => Eff r a Source

Makes an effect fail, preventing future effects from happening.

runExc :: Typeable e => Eff (Exc e :> r) a -> Eff r (Either e a) Source

Run a computation that might produce an exception.

catchExc :: (Typeable e, Member (Exc e) r) => Eff r a -> (e -> Eff r a) -> Eff r a Source

Run a computation that might produce exceptions, and give it a way to deal with the exceptions that come up.

Add a default value (i.e. failure handler) to a fallible computation. This hides the fact that a failure happened.

rethrowExc :: (Typeable e, Typeable e', Member (Exc e') r) => (e -> e') -> Eff (Exc e :> r) a -> Eff r a Source

Run a computation until it produces an exception, and convert and throw that exception in a new context.

liftEither :: (Typeable e, Member (Exc e) r) => Either e a -> Eff r a Source

Treat Lefts as exceptions and Rights as return values.

liftEitherM :: (Typeable m, Typeable e, Member (Exc e) r, SetMember Lift (Lift m) r) => m (Either e a) -> Eff r a Source

`liftEither`

in a lifted Monad