Thanks, and sorry for delayed reply.
I hadn't thought of doing it like how +++ does it, by just chaining the
pipes.
On Wednesday, July 9, 2014 3:20:12 AM UTC+10, Gabriel Gonzalez wrote:
>
> You can do this using `Pipes.Extras.(+++)`:
>
> p1 :: Pipe a d m r
> p2 :: Pipe b e m r
> p3 :: Pipe c f m r
>
> (p1 +++ p2) +++ p3 :: Pipe (Either (Either a b) c) (Either (Either d
> e) f) m r
>
> Then all you have to do is just stick `Pipes.Prelude.map` upstream of that
> to convert a `Signal` to a nested `Either`, and then also stick a
> `Pipes.Prelude.map` downstream of that to unify your handlers. I think it
> would look like this, but I haven't type-checked this yet:
>
> dispatcher :: Mode p p' e c m -> Pipe (Signal e c p) p' m ()
> dispatcher mode =
> Pipes.Prelude.map toEither
> >-> ((handlePacket mode +++ handleEvent mode) +++ handleCommand
> mode)
> >-> Pipes.Prelude.map fromEither
> where
> toEither s = case s of
> SigPacket p -> Left (Left p)
> SigEvent e -> Left (Right e)
> SigCommand c -> Right c
>
> fromEither e = case e of
> Left (Left p')) -> p'
> Left (Right p')) -> p'
> Right p' -> p'
>
> That will preserve the individual state of each handler.
>
> On 7/8/14, 8:09 AM, Kyle Van Berendonck wrote:
>
> I have a sum type which looks like this:
>
> data Signal e c p = SigEvent e | SigCommand c | SigPacket p
>
>
> I would like the user to be able to provide functions:
>
> type Handler p p' m = Pipe p p' m ()
>> data Mode p p' e c m = Mode
>> { handlePacket :: Handler p p' m
>> , handleEvent :: Handler e p' m
>> , handleCommand :: Handler c p' m }
>
>
> and have my single input pipe (dispatcher :: Pipe (Signal e c p) p' m
> ()) fork between the three handlers, while preserving the state of each.
> ie, one handling commands may use `await` but the next packet could be an
> event, so it would stay in await until a command arrives. One handler pipe
> quitting/finishing should result in all quitting.
>
> I would not like intermediate containers or forking threads to be part
> of the solution, since it will be a tight loop.
>
> Ideally, I need something like `next` which can be called in the other
> direction. Ideas?
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