Re: [Caml-list] Who was working on ocaml bindings for zeromq?

[Anders Peter Fugmann <anders@fugmann.net>]

Hi Goswin,

I cannot reproduce the type problems when mixing different socket types, 
including dealer socket type, in the polling interface.

Can you reproduce the same problems against the Issuu fork of ocaml-zmq, 
and post an example that exposes the problem?

Regards
Anders Fugmann


On 20/01/14 10:12, Goswin von Brederlow wrote:
> Yesterday I actually run into a problem with this. Creating a socket
> gave me a odd type (from memory):
>
> val stream: _[> `Push | `Pull | `Pub | `Sub | `Stream] ZMQ.Socket.t
> val dealer: _[> `Push | `Pull | `Pub | `Sub | `Dealer] ZMQ.Socket.t
>
> A few problems with that:
>
> 1) A stream socket should be just `Stream.
>
> 2) Note the _ there. The type is not polymorphic and gives an error
> that it can't be unified or something. Don't have the exact error in
> memory.
>
> I think there is something wrong with the way the socket types are
> specified that cause this. First time I ever got that kind of error.
>
> 3) Polling takes an ('a ZMQ.Socket.t, ZMQ.Socket.event) array. Trying
> to poll a stream and dealer socket causes type errors.
>
> I think phantom typed sockets are incompatible with putting them into
> an array outside the module. This needs an interface where you have a
> poller instance and can add sockets to it one at a time. Internally
> the phantom type is known to be "phantom" and the sockets can be put
> into an array, hashtbl or list.
>
> I didn't have time yet to look into those problems. Currently I used
> Obj.magic to make it work because I wanted to work on the application
> instead of on zmq. But that certainly isn't a solution.
>
>
> So in summary: We need a new polling interface (or phantom typing).
> Not just because I don't like it but because it doesn't work for
> combining different socket types.
>
> MfG
> 	Goswin
>