Hi Hans, Do you have a denotation for your representation (a specification for your implementation)? If so, it will likely guide you to exactly the right type class instances, via the principle of type class morphisms<http://conal.net/papers/type-class-morphisms/>(TCMs). If you don't have a denotation, I wonder how you could decide what correctness means for any aspect of your implementation.
Good luck, and let me know if you want some help exploring the TCM process, -- Conal On Tue, Apr 23, 2013 at 6:22 AM, Hans Höglund <[email protected]> wrote: > Hi everyone, > > I am experimenting with various implementation styles for classical FRP. > My current thoughts are on a continuation-style push implementation, which > can be summarized as follows. > > > newtype EventT m r a = E { runE :: (a -> m r) -> m r -> m r } > > newtype ReactiveT m r a = R { runR :: (m a -> m r) -> m r } > > type Event = EventT IO () > > type Reactive = ReactiveT IO () > > The idea is that events allow subscription of handlers, which are > automatically unsubscribed after the continuation has finished, while > reactives allow observation of a shared state until the continuation has > finished. > > I managed to write the following Applicative instance > > > instance Applicative (ReactiveT m r) where > > pure a = R $ \k -> k (pure a) > > R f <*> R a = R $ \k -> f (\f' -> a (\a' -> k $ f' <*> a')) > > But I am stuck on finding a suitable Monad instance. I notice the > similarity between my types and the ContT monad and have a feeling this > similarity could be used to clean up my instance code, but am not sure how > to proceed. Does anyone have an idea, or a pointer to suitable literature. > > Best regards, > Hans > > _______________________________________________ > Haskell-Cafe mailing list > [email protected] > http://www.haskell.org/mailman/listinfo/haskell-cafe > >
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