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 LAA28152; Mon, 14 Jun 2004 11:29:03 +0200 (MET DST)
X-Authentication-Warning: pauillac.inria.fr: majordomo set sender to owner-caml-list@pauillac.inria.fr using -f
Received: from nez-perce.inria.fr (nez-perce.inria.fr [192.93.2.78]) by pauillac.inria.fr (8.7.6/8.7.3) with ESMTP id LAA25154 for <caml-list@pauillac.inria.fr>; Mon, 14 Jun 2004 11:29:02 +0200 (MET DST)
Received: from postfix4-1.free.fr (postfix4-1.free.fr [213.228.0.62])
	by nez-perce.inria.fr (8.12.10/8.12.10) with ESMTP id i5E9T1EV016986
	for <caml-list@inria.fr>; Mon, 14 Jun 2004 11:29:02 +0200
Received: from [192.168.2.8] (auteuil-1-81-57-2-20.fbx.proxad.net [81.57.2.20])
	by postfix4-1.free.fr (Postfix) with ESMTP id 51AE310DF71
	for <caml-list@inria.fr>; Mon, 14 Jun 2004 11:29:01 +0200 (CEST)
Subject: Re: [Caml-list] troubles with polymorphic variant in class
From: =?ISO-8859-1?Q?Fran=E7ois-Xavier?= HOUARD <IdeFX@Iname.com>
Reply-To: IdeFX@Iname.com
To: caml-list@inria.fr
In-Reply-To: <1087149590.16811.1342.camel@pelican.wigram>
References: <1087142756.10383.50.camel@Bess>
	 <1087149590.16811.1342.camel@pelican.wigram>
Content-Type: text/plain; charset=ISO-8859-15
Message-Id: <1087205340.8886.4.camel@Bess>
Mime-Version: 1.0
X-Mailer: Ximian Evolution 1.4.6 
Date: Mon, 14 Jun 2004 11:29:01 +0200
Content-Transfer-Encoding: 8bit
X-Miltered: at nez-perce with ID 40CD6FDD.001 by Joe's j-chkmail (http://j-chkmail.ensmp.fr)!
X-Loop: caml-list@inria.fr
X-Spam: no; 0.00; caml-list:01 iname:99 2004:99 fixpoint:01 widget:01 widget:01 unwieldy:01 uglier:01 struct:01 gui:01 extensible:01 coca-ml:01 ecrit:01 polymorphic:01 equation:01 
Sender: owner-caml-list@pauillac.inria.fr
Precedence: bulk

Le dim 13/06/2004 à 19:59, skaller a écrit :

> (* fixpoint *)
> type widget = 'w widget' as 'w 
> 
> which effectively solves the type equation
> 'w = 'w widget (and names the result widget).
> Now define non-polymorphic classes:
> 
> class button = [widget] button'
> class window = [widget] window'
> 
> This is not so bad for a single parameter 'w.
> For multiple parameters the notation soon becomes
> too unwieldy to be practical. 

But the answer you gave me, which I find quite nice, don't allow my user
to add his own class....
I could do the stuff with a parametrized module (the parameter given by
the user would contain the variant used in the program... Including the
ones of my library!!), or, even uglier, use a close variant in my
module, which would be like:
[ Window of window | Frame of frame | User_variant of 'a ]

And 'a, the parameter of the module, given by the user, would also be a
variant...

module SillyModule =
struct
	type t = [ MyWindow of myWindow | MyText of myText ];;
end
;;
module myGui = Gui (SillyModule);;
let a = new Window;;
let x = new myText a;;
let l = a#get_child in
match l with
h::t -> (match h with 
	 	myGui.User_variant v ->
			( match v with
			    MyText t -> .......
			    | _ ->
			)
		| _ -> raise Not_found
	)
....


Who the hell would use this ??? 

So, if I can't find a better solution, i could still try to find a
sado-m(l)asochist mailing list, to find potential users !

;))


Let's be more serious. What you said is fine, but, please, tell me there
is an easier solution to make it work with user defined class...
Please....

Thanks for all

FX Houard, desperate to find an elegant and extensible solution to his
problem... And attracted by the dark-dynamic-typed side of coca-ml.

-------------------
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