From: Alessandro Baretta <alex@baretta.com>
To: Michael Vanier <mvanier@cs.caltech.edu>
Cc: Ocaml <caml-list@inria.fr>
Subject: Re: [Caml-list] coercions from superclass to subclass?
Date: Fri, 07 Jun 2002 12:17:59 +0200 [thread overview]
Message-ID: <3D008857.2000501@baretta.com> (raw)
In-Reply-To: <200206062215.g56MF5w19818@orchestra.cs.caltech.edu>
Michael Vanier wrote:
> I understand that there is no mechanism to coerce from a superclass to a
> subclass in ocaml (i.e. the equivalent of C++'s run-time type
> identification or java's instanceof operator). Are there any plans to add
> such a capability in the future?
>
> Mike
Jacques Garrigue gave the following explanation a week ago.
> By the way, here is a simple way to do downcasts, when
> really needed.
>
> # let tbl : (< >, impl) Hashtbl.t = Hashtbl.create 17
> let register obj = Hashtbl.add tbl (obj :> < >) obj
> let recover obj = Hashtbl.find tbl (obj :> < >) ;;
> val tbl : (< >, impl) Hashtbl.t = <abstr>
> val register : impl -> unit = <fun>
> val recover : < .. > -> impl = <fun>
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next prev parent reply other threads:[~2002-06-07 10:12 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-06-06 22:15 Michael Vanier
2002-06-07 10:17 ` Alessandro Baretta [this message]
2002-06-07 10:47 ` Jacques Garrigue
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