On Fri, May 10, 2013 at 9:00 AM, Andres Löh
This twist is very simple to deal with if you have real existential types, with the relevant part of the interface looking approximately like
init :: exists a. IO (Inotify a) addWatch :: Inotify a -> FilePath -> IO (Watch a) rmWatch :: Inotify a -> Watch a -> IO ()
You can still do the ST-like encoding (after all, the ST typing trick is just an encoding of an existential), with init becoming "like runST":
init :: (forall a. Inotify a -> IO b) -> IO b addWatch :: Inotify a -> FilePath -> IO (Watch a) rmWatch :: Inotify a -> Watch a -> IO ()
Right, but my interface the Inotify descriptor has an indefinite extent, whereas your interface enforces a dynamic extent. I'm not sure to what degree this would impact use cases of this particular library, but in general moving a client program from the the first interface to the second can require significant changes to the structure of the program, whereas moving a client program from the second interface to the first is trivial. So I'd say my interface is more expressive. Best, Leon