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From: Erkki Seppala <flux-caml@inside.org>
To: caml-list@yquem.inria.fr
References: <20130513094015.GB8366@frosties>
Date: Mon, 13 May 2013 15:11:05 +0300
In-Reply-To: <20130513094015.GB8366@frosties> (Goswin von Brederlow's message
	of "Mon, 13 May 2013 11:40:15 +0200")
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Subject: Re: [Caml-list] RFH: type / consistency problem

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.

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