220 30215 <87adf165-dd56-e16f-e4ab-c14931921540@wanadoo.fr> article Path: news.gmane.org!.POSTED!not-for-mail From: "Vicente J. Botet Escriba" Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: enum_cast proposal Date: Wed, 4 Jan 2017 08:13:30 +0100 Lines: 48 Approved: news@gmane.org Message-ID: <87adf165-dd56-e16f-e4ab-c14931921540@wanadoo.fr> References: <1d5db671-8ee9-49dc-937d-10a20f48fe73@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1483514021 22520 195.159.176.226 (4 Jan 2017 07:13:41 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 4 Jan 2017 07:13:41 +0000 (UTC) User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:45.0) Gecko/20100101 Thunderbird/45.6.0 Cc: m.cencora@gmail.com To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDH67CONY4PBBGWBWLBQKGQEN67YYTQ@isocpp.org Wed Jan 04 08:13:34 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-wj0-f199.google.com ([209.85.210.199]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cOflH-00049H-8n for gclcip-std-proposals@m.gmane.org; Wed, 04 Jan 2017 08:13:27 +0100 Original-Received: by mail-wj0-f199.google.com with SMTP id hb5sf114285730wjc.2 for ; Tue, 03 Jan 2017 23:13:31 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=subject:to:references:cc:from:message-id:date:user-agent :mime-version:in-reply-to:content-transfer-encoding :x-original-sender:x-original-authentication-results:reply-to :precedence:mailing-list:list-id:x-spam-checked-in-group:list-post :list-help:list-archive:list-subscribe:list-unsubscribe; bh=3hgLliZVuWrfxI1f07v80C45Ii6pT0RdtKE9ONfWLEw=; b=I6EVEZPVXXv2JO9mZpV1cJNJfLFlDDIQ3nXewZyEILizit0ti8qNqgGy4hQdz1vpre D/HxuyYA/wQUg47XGyFKSblxU7gM2HqKDWxmGl+KSPAcP81CMcwnfviyvNO9nxb+JCqQ EogD5VRNMW7jeCYXwgneOqGrnI6Fz2LNP7fx2abJfsQhUtoeSDqOT88gNnHyfbN0NhVK ilFh4HaHzLRdtfQD8H6DmuY2+OEihuW2VArg9ju9kEtfxLTj33J8b9kY3pZoV8ph6Ozu 9j8jTizS+ErPkFi+8CkVMOFf2SdLg921srPuDSq9Geavn77flMZmV47zC7vnv4VNweLs X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:cc:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :x-original-sender:x-original-authentication-results:reply-to :precedence:mailing-list:list-id:x-spam-checked-in-group:list-post :list-help:list-archive:list-subscribe:list-unsubscribe; bh=3hgLliZVuWrfxI1f07v80C45Ii6pT0RdtKE9ONfWLEw=; b=eiUO3NeCgSOhad380jl7XDxkniZPPN7d10Td2nQFCexVICIVSLYXINE25OR9cvNqmE ZxTo+px0NmRqxIwgHGhEgEk7tnUOkKH4FdnyjABQgTGwtoeQMYMWoxJ8C7bOAyxYGbV5 fvd23DFBnl1WyAQd36yBj0ynSBjVmxJCvFhijDNbZRky+AaCpFGki0r9RxSGeSVyV7Ul 9HRvvIDXfp3KSPgks/NZ+Q/Mp/RhvtZ2/Hjy4O5ss1/dBFcymojQsOEubkWvlUlCfLPH wgSvA/aXPnSzzXXvHXcUetBz+5vBO1dzlAA24oZadqESBXQXRk6D9qa0RsCHIxwewAV X-Gm-Message-State: AIkVDXKo9nJkAYgZwegJtBq12aDfEpaBsvhBFVtPqOhB3x5klyv5P5zHX21yux8RZU8LJw== X-Received: by 10.28.26.72 with SMTP id a69mr1581585wma.4.1483514011626; Tue, 03 Jan 2017 23:13:31 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.28.45.80 with SMTP id t77ls80106wmt.25.canary-gmail; Tue, 03 Jan 2017 23:13:30 -0800 (PST) X-Received: by 10.194.71.17 with SMTP id q17mr66297298wju.180.1483514010412; Tue, 03 Jan 2017 23:13:30 -0800 (PST) Original-Received: from smtp.smtpout.orange.fr (smtp09.smtpout.orange.fr. [80.12.242.131]) by mx.google.com with ESMTPS id 12si76641269wms.74.2017.01.03.23.13.30 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 03 Jan 2017 23:13:30 -0800 (PST) Received-SPF: neutral (google.com: 80.12.242.131 is neither permitted nor denied by best guess record for domain of vicente.botet@wanadoo.fr) client-ip=80.12.242.131; Original-Received: from imac-de-vicente-botet-escriba.home ([92.139.156.24]) by mwinf5d69 with ME id U7DV1u00K0Xrduc037DVEg; Wed, 04 Jan 2017 08:13:30 +0100 X-ME-Helo: imac-de-vicente-botet-escriba.home X-ME-Auth: dmljZW50ZS5ib3RldEB3YW5hZG9vLmZy X-ME-Date: Wed, 04 Jan 2017 08:13:30 +0100 X-ME-IP: 92.139.156.24 In-Reply-To: <1d5db671-8ee9-49dc-937d-10a20f48fe73@isocpp.org> X-Original-Sender: vicente.botet@wanadoo.fr X-Original-Authentication-Results: mx.google.com; spf=neutral (google.com: 80.12.242.131 is neither permitted nor denied by best guess record for domain of vicente.botet@wanadoo.fr) smtp.mailfrom=vicente.botet@wanadoo.fr Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:30215 Archived-At: Le 04/01/2017 =C3=A0 00:48, gmisocpp@gmail.com a =C3=A9crit : > > Just considering my earlier make_enum comment further, The ultimate=20 > minimum for C++ is surely this?: > > traffic_light light{}; // whatever default. > bool guaranteed_success =3D std::can_cast_enum(x); > if (guaranteed_success) > light =3D reinterpret_cast(x); > // else error condition. > > It separates the validity check from the conversion and then you can=20 > build whatever on that, i.e. assign, atomic assign, etc. > This seems more C++ like, but forgets C, which probably people feel is=20 > not a concern anyway. > But other wise some special C and C++ syntax like=20 > can_cast_enum(traffic_light, x) would seem to cover both languages if=20 > that's desirable. Yes, this is the good interface :) I'm all for a proposal of this minimal interface, even if I would add a=20 enum_cast synonym of static_cast. It is clear from the previous code that there is no problem with the=20 cast and using the same name would surely help const traffic_light light =3D (std::can_enum_cast(x))= =20 ? std::enum_cast(x) :=20 throw_bad_enum_cast(x); Note that throw_bad_enum_cast is not proposed. It is only and example to=20 show the interface allows the use of safe conversions expressions. We could see later what can be built on top of it and what could be on=20 the standard. Vicente --=20 You received this message because you are subscribed to the Google Groups "= ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. To view this discussion on the web visit https://groups.google.com/a/isocpp= ..org/d/msgid/std-proposals/87adf165-dd56-e16f-e4ab-c14931921540%40wanadoo.f= r. .