Work in m (Either e a), where Left is for domain errors and exceptions are for programmer errors. Thoughts?
You must log in to comment.
in reply to @Quelklef's post:
Yes, but why not ExceptT e m a? That's what I would use (but with a concrete m and hidden behind a newtype with deriving newtype (MonadError e))
actually, wouldn't having the MonadError instance be inherited from Either mean that you cannot throw or catch exceptions in m?
i feel like i'd be down to work in ExceptT e m a directly, though, that sounds fun
i guess if the m-exceptions are supposed to be the irrecoverable ones then it makes sense to not be able to throw/catch them
hmm so by "exceptions in m", do you mean imprecise exceptions (as in error) or IO exceptions? imprecise exceptions should pretty much "just work", but if you need IO exceptions, you can always manually lift the functions out of your newtype (as in throwProgrammerError = MkYourMonad . throw).
but I guess recovering from programmer errors doesn't make much sense from inside the monad anyway.
what I like about the newtype approach is that you're in control about how much of the underlying error handling mechanisms you expose. if you decide you want to allow catching exceptions, you can just expose that but if you don't, you don't have to.
Pinned Tags