220 29268 article Path: news.gmane.org!.POSTED!not-for-mail From: Andrzej Krzemienski Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: explicit conversion from enum class to its underlying type Date: Mon, 31 Oct 2016 09:14:59 +0100 Lines: 94 Approved: news@gmane.org Message-ID: References: <4afed494-4fc5-4b06-b3e7-255aa293068e@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=e89a8fb1eae8d94dac054024cdb5 X-Trace: blaine.gmane.org 1477901721 26151 195.159.176.226 (31 Oct 2016 08:15:21 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 31 Oct 2016 08:15:21 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDT2DGOJ34DBBB733PAAKGQEGX3KI4A@isocpp.org Mon Oct 31 09:15:17 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-wm0-f70.google.com ([74.125.82.70]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1c17kC-0004O6-W7 for gclcip-std-proposals@m.gmane.org; Mon, 31 Oct 2016 09:15:01 +0100 Original-Received: by mail-wm0-f70.google.com with SMTP id 79sf64818319wmy.6 for ; Mon, 31 Oct 2016 01:15:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :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=GYZ6Sm0QqcdRkAAGA6NSJ/ox78n6FLI9ciG71GxyhlI=; b=W0a6YOqgmowQ8lAVxuWa5sqmBp1DNHxQQZLzY8sSMXR+6rdbx5TLo75ojoefP2xihy 6mSDjjZziuDWNkzipJhv6+ujRi9gmt8O3I0yQ07AFHFgswJH+SVeSSmJtMAeGFQeKm6n ddGggBtOzN0kL4T8hVZ6NDuJYmYJPnBEVnk7J13PgIaGUEwXpPE/F/u6YktmVlEjENmZ b13/jskbO2ze9dsUID3iOWYB/R3zyW3yVWQhMxdBQS0r2E6/UMFX5Hac2DChhU4sE+bl RWk9U2qqx31g7GltJSQKUVMuoHpR5eP0r+E8QLoZs4vfjxqq+1Ts9iinhXFN6XnZg8GX GEXQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to: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=GYZ6Sm0QqcdRkAAGA6NSJ/ox78n6FLI9ciG71GxyhlI=; b=G5XkflxTSBD4oDenG60EOdwKuccwfiazmUU6GlEhsz0Wm7oR88CnL2kQqmFcveV8hT 5Bv+X7BUsw4stta3de3j/LntKyVgVJVnoNPjeywtidmrgBcBHOjH0eorTuuRZIWr0MmO gFqTKDVzdrx6gkpS09Zi95lEbD0Xpr3lvkiZ701mbqVwO0mF2e7doMS3PmtxmuVs4/yp 4AuSHbPfqM3aWZ13ZCJL+BC/ZmB05JrHxR0B/Qhkb7HMEGL/kw2fGL0bIkgyKMOupIh8 vw6rnsAlrmpCfE0q0TCsGBSAaXKTl8VI7w6WxzZPu8Gmc3PT5DS9zUsl5P/dnjrWC787 iD7g== X-Gm-Message-State: ABUngvfD9MUeAcFgRhxU1/qcWBF/9xhHpPaUbTsIIzONIPlr6CfSNiZdFv9oF9QxHTpRDA== X-Received: by 10.28.26.10 with SMTP id a10mr721690wma.20.1477901703869; Mon, 31 Oct 2016 01:15:03 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.28.165.9 with SMTP id o9ls1326226wme.5.gmail; Mon, 31 Oct 2016 01:15:00 -0700 (PDT) X-Received: by 10.194.68.106 with SMTP id v10mr21483568wjt.149.1477901700640; Mon, 31 Oct 2016 01:15:00 -0700 (PDT) Original-Received: from mail-wm0-x234.google.com (mail-wm0-x234.google.com. [2a00:1450:400c:c09::234]) by mx.google.com with ESMTPS id me20si28159442wjb.81.2016.10.31.01.15.00 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 31 Oct 2016 01:15:00 -0700 (PDT) Received-SPF: pass (google.com: domain of akrzemi1@gmail.com designates 2a00:1450:400c:c09::234 as permitted sender) client-ip=2a00:1450:400c:c09::234; Original-Received: by mail-wm0-x234.google.com with SMTP id n67so213516163wme.1 for ; Mon, 31 Oct 2016 01:15:00 -0700 (PDT) X-Received: by 10.194.106.169 with SMTP id gv9mr21017977wjb.129.1477901700122; Mon, 31 Oct 2016 01:15:00 -0700 (PDT) Original-Received: by 10.80.186.55 with HTTP; Mon, 31 Oct 2016 01:14:59 -0700 (PDT) In-Reply-To: X-Original-Sender: akrzemi1@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com; spf=pass (google.com: domain of akrzemi1@gmail.com designates 2a00:1450:400c:c09::234 as permitted sender) smtp.mailfrom=akrzemi1@gmail.com; dmarc=pass (p=NONE dis=NONE) header.from=gmail.com 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:29268 Archived-At: --e89a8fb1eae8d94dac054024cdb5 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable 2016-10-30 2:31 GMT+02:00 Nicol Bolas : > On Saturday, October 29, 2016 at 5:51:12 PM UTC-4, Andrzej Krzemie=C5=84s= ki > wrote: >> >> Hi All, >> >> One of the nice safety features of enum classes is that they cannot be >> implicitly converted to their underlying type. However, do you think we >> would lose this safety feature if we allowed an explicit conversion to t= he >> underlying type? >> >> I do not know of any practical use of explicit conversion operators >> except for the contextual conversion to bool. And it is only this >> conversion that I am interested in. >> > > So, what you're asking for is if the underlying type of a strong enum is > `bool`, then that type can be contextually converted to `bool`. I don't > think it's worth adding a language feature for such an incredibly narrow > corner case. > > But are you saying that the process of pushing this change into the language is too expensive to warrant the satisfaction of a marginal use case? Or are you saying that satisfying one small use case is over-weighed by potential type safety hole that would come with the change? Regards, &rzej; --=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/CAOenAXg3vcFOkVFd8MWXuBeDE4rJhSK15SrK2KeAGZLBY4k= POg%40mail.gmail.com. --e89a8fb1eae8d94dac054024cdb5 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable


2016-10-30 2:31 GMT+02:00 Nicol Bolas <jmckesson@gmail.com>:
= On Saturday, October 29, 2016 at 5:51:12 PM UTC-4, Andrzej Krzemie=C5=84ski= wrote:
Hi All,
=
One of the nice safety features of enum classes is that they cannot be = implicitly converted to their underlying type. However, do you think we wou= ld lose this safety feature if we allowed an explicit conversion to the und= erlying type?

I do not know of any practical use of explicit convers= ion operators except for the contextual conversion to bool. And it is only = this conversion that I am interested in.
=
So, what you're asking for is if the underlying type of a strong en= um is `bool`, then that type can be contextually converted to `bool`. I don= 't think it's worth adding a language feature for such an incredibl= y narrow corner case.

But are you saying that the process of push= ing this change into the language is too expensive to warrant the satisfact= ion of a marginal use case? Or are you saying that satisfying one small use= case is over-weighed by potential type safety hole that would come with th= e change?

Regards,
&rzej;

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