Help with Event Effect

[dark-ether]

i am trying to create a event effect, basically it would have 2 operations registerHandler which would add the given action to a list and raiseEvent which would call all actions with the given argument so if using a dynamic effect we could have the following

data Event e m a where
  RegisterHandler :: (e -> m ()) -> Event e m ()
  RaiseEvent :: e -> Event e m ()
registerHandler ::Event e :> es => (e -> Eff es ()) -> Eff es ()
registerHandler = send . RegisterHandler
raiseEvent :: Event e :> es => e -> Eff es ()
raiseEvent = send . RaiseEvent
type instance DispatchOf (Event e) = 'Dynamic

the problem comes when we try to implement it
i tried

runEvent ::forall e es a. Eff (Event e ': es) a -> Eff es a
runEvent = reinterpret (evalState ([]::[e -> Eff es ()])) $ \env -> \case
  (RegisterHandler act) -> localUnlift env (ConcUnlift Persistent Unlimited) $ \unlift  -> modify @([e -> Eff es ()]) ((unlift . act) :)

however this fails as (unlift . act) outputs a e -> Eff (State [e -> Eff es ()] ': es) () and not the wanted e -> Eff es ()
so the simple fix of changing the type of our state won't work as then we would have a infinite type.
thanks in advance for any insight

[arybczak]

You need raiseWith:

runEvent ::forall e es a. Eff (Event e ': es) a -> Eff es a
runEvent = reinterpret (evalState ([]::[e -> Eff es ()])) $ \env -> \case
  (RegisterHandler act) -> raiseWith SeqUnlift $ \lower -> do
    localUnlift env (ConcUnlift Persistent Unlimited) $ \unlift -> lower $ do
      modify ((unlift . act) :)

[dark-ether]

thanks i swear i tried using raiseWith, must have swapped something