From mboxrd@z Thu Jan  1 00:00:00 1970
Received: (from majordomo@localhost) by pauillac.inria.fr (8.7.6/8.7.3) id PAA22763; Tue, 3 Aug 2004 15:17:19 +0200 (MET DST)
X-Authentication-Warning: pauillac.inria.fr: majordomo set sender to owner-caml-list@pauillac.inria.fr using -f
Received: from concorde.inria.fr (concorde.inria.fr [192.93.2.39]) by pauillac.inria.fr (8.7.6/8.7.3) with ESMTP id PAA22744 for <caml-list@pauillac.inria.fr>; Tue, 3 Aug 2004 15:17:18 +0200 (MET DST)
Received: from annexia.force9.co.uk (annexia.force9.co.uk [212.56.101.183])
	by concorde.inria.fr (8.12.10/8.12.10) with ESMTP id i73DHHSH029023
	for <caml-list@inria.fr>; Tue, 3 Aug 2004 15:17:17 +0200
Received: from rich by annexia.force9.co.uk with local (Exim 3.36 #1 (Debian))
	id 1BrzAK-00067e-00
	for <caml-list@inria.fr>; Tue, 03 Aug 2004 14:17:16 +0100
Date: Tue, 3 Aug 2004 14:17:16 +0100
To: caml-list@inria.fr
Subject: Re: [Caml-list] Functors and classes
Message-ID: <20040803131716.GA22773@annexia.org>
References: <20040803120244.GA22304@annexia.org> <20040803121049.GA22418@annexia.org>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20040803121049.GA22418@annexia.org>
User-Agent: Mutt/1.5.5.1+cvs20040105i
From: Richard Jones <rich@annexia.org>
X-Miltered: at concorde with ID 410F905D.000 by Joe's j-chkmail (http://j-chkmail.ensmp.fr)!
X-Loop: caml-list@inria.fr
X-Spam: no; 0.00; caml-list:01 functors:01 mli:01 val:01 dbi:99 dbi:99 compiles:01 instantiate:01 postgres:01 mismatch:01 postgres:01 ltd:98 bool:01 bool:01 caml:01 
Sender: owner-caml-list@pauillac.inria.fr
Precedence: bulk

OK, I have another problem.

My apache.mli now looks like this:

----------------------------------------------------------------------
module type DbiConnection = sig

  class connection : ?host:string -> ?port:string ->
			      ?user:string -> ?password:string -> string ->
  object
    method close : unit -> unit
    method closed : bool
    method ping : unit -> bool
    method rollback : unit -> unit
  end

end

module type DbiPoolT = sig

  type connection

  val get : Request.t -> ?host:string -> ?port:string ->
    ?user:string -> ?password:string -> string -> connection
end

module DbiPool (Dbi : DbiConnection) : DbiPoolT
  with type connection = Dbi.connection
----------------------------------------------------------------------

This compiles fine, with the corresponding .ml file.  However when
I try to instantiate a pool using:

module Pool = DbiPool (Dbi_postgres)

I get errors:

File "examples/useful-scripts/maillist.ml", line 49, characters 23-35:
Signature mismatch:
Modules do not match:
[...]
The public method commit cannot be hidden
The public method database cannot be hidden
The public method database_type cannot be hidden
[etc.]

I understand why this happens, because the actual Dbi_postgres.-
connection class is much more complicated than the mere four methods
which I need to use to make the pool work.

However, importing the entire class type is complex in three respects:
it depends on a bunch of other classes which need to be imported; and
it means that a particular version of mod_caml becomes very dependent
on a particular version of ocamldbi; and (crucially, fatally) the
different database subclasses may all contain extra and different
public methods, so there is no way to list all the public methods
anyway.

I tried to define an "open class" (<method; method; ..>) using:

module type DbiConnection = sig

  class connection : ?host:string -> ?port:string ->
			      ?user:string -> ?password:string -> string ->
    < close : unit -> unit;
      closed : bool;
      ping : unit -> bool;
      rollback : unit -> unit; .. >

end

but this gives a syntax error.

Ideas on how to solve this one?

Rich.

-- 
Richard Jones. http://www.annexia.org/ http://www.j-london.com/
Merjis Ltd. http://www.merjis.com/ - improving website return on investment
NET::FTPSERVER is a full-featured, secure, configurable, database-backed
FTP server written in Perl: http://www.annexia.org/freeware/netftpserver/

-------------------
To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr
Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/
Beginner's list: http://groups.yahoo.com/group/ocaml_beginners