Re: [Caml-list] RFH: type / consistency problem

[Goswin von Brederlow <goswin-v-b@web.de>]

On Mon, May 13, 2013 at 03:11:05PM +0300, Erkki Seppala wrote:
> Something like this?
> 
> module Protocol : sig
>   type 'a request
>   type 'a reply
>   type session
> 
>   val issue : session -> 'a request -> 'a
> 
>   type foo_response = { fr_s : string }
>   val foo : string -> foo_response request
> 
>   type bar_response = int
>   val bar : int -> bar request
> 
>   type baz_response = unit
>   val baz : unit -> baz request
> end = struct
>   type 'a reply = string -> 'a
>   type 'a request = {
>     req_type : int;
>     req_data : string;
>     req_handle : 'a reply
>   }
> 
>   type foo_response = { fr_s : string }
>   
>   let issue session request =
>     send (request.req_type, request.req_data);
>     request.req_handle (receive ())
> 
>   let foo int = 
>     let handle_foo_response str =
>       { fr_s = str }
>     in
>       { req_type = 42; req_data = Printf.sprintf "hello %d" int;
>         req_handle = handle_foo_response }
> 
>   (* etc *)
> end
> 
> The nice thing about this is that you can support synchronous and
> asynchronous communication with essentially the same interface of
> constructing messages, you just have a different kind of issue function.

There is no connection between the 'a of a request, req_type and the
req_data. req_data isn't even the raw data anymore but, I assume,
already the serialized data ready for sending. So you have gone from 2
independet types to 3. I could create a foo_responce request with
req_type = Bar containing the data for type Buzz.

And what about the server? It reads requests from the network and has
to send out matching replies. I'm actually more interested in that
side, but both should work and have the same common type.

MfG
	Goswin