From mboxrd@z Thu Jan  1 00:00:00 1970
Received: (from weis@localhost) by pauillac.inria.fr (8.7.6/8.7.3) id LAA30989 for caml-redistribution; Mon, 31 May 1999 11:49:53 +0200 (MET DST)
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 WAA29091 for <caml-list@pauillac.inria.fr>; Sun, 30 May 1999 22:23:18 +0200 (MET DST)
Received: from fermi.cnam.fr (fermi.cnam.fr [163.173.128.60])
	by nez-perce.inria.fr (8.8.7/8.8.7) with ESMTP id WAA10766
	for <caml-list@inria.fr>; Sun, 30 May 1999 22:23:17 +0200 (MET DST)
Received: from 163.173.128.93 (phone-client.cnam.fr [163.173.128.93])
	  by fermi.cnam.fr (8.8.8/jpm-301097)  with SMTP id WAA19888
	  ; Sun, 30 May 1999 22:23:15 +0200 (MET DST)
Message-ID: <37519E82.7D14@cnam.fr>
Date: Sun, 30 May 1999 22:24:35 +0200
From: Olivier Chararas <charar_o@cnam.fr>
Organization: Critical lack of
X-Mailer: Mozilla 3.04 (Macintosh; I; 68K)
MIME-Version: 1.0
To: caml-list@inria.fr
Subject: OCAML parametric class coercion
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Sender: weis

(*
NAIVE REQUEST :
In this design the ellipsis won't be bound so I wanted to use coercion
but I can't figure out how to express the coercion with respect to
the parametric type.

Can you help me on syntax?
Or is the problem more fundamental?
Is this bad design anyway?

Thanks
*)

# class ['a] truc(init,(dev:'a)) =
  object(self)
   method essai = 1
  end
  ;;
class ['a] truc : 'b * 'a -> object method essai : int end
# 
  class ['a] bidu1((dev:'a)) =
  object(self)
   method rate(untruc) = untruc#essai
  end
  ;;
Some type variables are unbound in this type:
  class ['a] bidu1 : 'a -> object method rate : < essai : 'b; .. > -> 'b
end
The method rate has type < essai : 'a; .. > -> 'a where .. is unbound
# 
  class ['a] bidu2((dev:'a)) =
  object(self)
   method rate(untruc:truc) = untruc#essai
  end
  ;;
The type constructor truc expects 1 argument(s),
but is here applied to 0 argument(s)