On Fri, May 10, 2013 at 9:00 AM, Andres Löh <and...@well-typed.com> wrote:
> > 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
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