220 27949 article Path: news.gmane.org!.POSTED!not-for-mail From: "'Jeffrey Yasskin' via ISO C++ Standard - Future Proposals" Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Make (strongly typed) enums castable to char const * const Date: Thu, 25 Aug 2016 11:39:36 -0700 Lines: 126 Approved: news@gmane.org Message-ID: References: <1472132849.17129.9.camel@bsdforen.de> <1472148645.17129.15.camel@bsdforen.de> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=001a113fe54075d944053ae9b97a X-Trace: blaine.gmane.org 1472150404 30804 195.159.176.226 (25 Aug 2016 18:40:04 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 25 Aug 2016 18:40:04 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDDM34EO6QDRB7PW7S6QKGQEZ4EUVLQ@isocpp.org Thu Aug 25 20:40:00 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ua0-f198.google.com ([209.85.217.198]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1bczZH-0007Rt-7m for gclcip-std-proposals@m.gmane.org; Thu, 25 Aug 2016 20:39:59 +0200 Original-Received: by mail-ua0-f198.google.com with SMTP id r91sf105766611uar.0 for ; Thu, 25 Aug 2016 11:40:00 -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=TRGalCCkw16DLKtTjl9PuFOh3NNIkIHU5uTl52DwR3A=; b=R484PQkVXx4TKquKckPZvWbsXqx1Iac5lPcdfLItwiHaBqyvmDWNuoadQOi4YcTBl9 MXuyAIP252tO9GFNy0SvOKUnDh715SYt0HW+Tok3Z/lhPOPIihKUSgWqqkHQ/zUgf2hl h/3nssnxkFAYLauMi8F/3+uO9zM9h6uncX6+j9kY8kYsHymbIbwtWej+mIFPLBGJxYem LdwuXlM5zOW7MWU0RvekLx19DNLWwT7jpa7Gc8HtO5v7OPb0s/EkVlXrBFqSIggprsH7 g/u6O+dTM26Pggr/Wxo4+3qJMnllQ8QJ5hSDKJhGXIRGMMjuJ0uw2bNDWRAbXjZVStXn 1A9g== 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=TRGalCCkw16DLKtTjl9PuFOh3NNIkIHU5uTl52DwR3A=; b=Pcwpp0+5Hm6CqFStHx7LnOJCAMppLMfM/R4o9RTwyo0Y+i8c2y850xkm6PbnJU9SOH 2i+vCkKOGcFcGVaNDPxUDhNaRbz7x2ZAesd63IGgShHeIWCHUifh/YcBbF4pl27NJBnj RblFbnlDSeiD08nfFkFsLWnfJOp9YvUjq9K6aJlQtHy+knA1bCDOGqgs1MNeTCqaNFxh eBW2GlNpjJRvOIX3UiA2q4rhs25ZOKjyc6iTtHxmEuJBYKSEf6dK4lqAXxg5pz3AqaFm f0mdrj8lwYauUGWRWqyS1i14C6HxdGXLnflYSfX2bde9jxdBarwN9ktgMFuq016aGkip PVtg== X-Gm-Message-State: AE9vXwN8RU2oCENVbgTUMLRoLREMuxX6bACWcjGCE5GEBtRKqSUSn9ONfoQA4YD3h3oIWA== X-Received: by 10.129.155.142 with SMTP id s136mr6771611ywg.22.1472150398863; Thu, 25 Aug 2016 11:39:58 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.169.101 with SMTP id s98ls668535ioe.53.gmail; Thu, 25 Aug 2016 11:39:57 -0700 (PDT) X-Received: by 10.107.160.202 with SMTP id j193mr12039217ioe.23.1472150397601; Thu, 25 Aug 2016 11:39:57 -0700 (PDT) Original-Received: from mail-it0-x22a.google.com (mail-it0-x22a.google.com. [2607:f8b0:4001:c0b::22a]) by mx.google.com with ESMTPS id k21si19663185iok.96.2016.08.25.11.39.57 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 25 Aug 2016 11:39:57 -0700 (PDT) Received-SPF: pass (google.com: domain of jyasskin@google.com designates 2607:f8b0:4001:c0b::22a as permitted sender) client-ip=2607:f8b0:4001:c0b::22a; Original-Received: by mail-it0-x22a.google.com with SMTP id e63so34813125ith.1 for ; Thu, 25 Aug 2016 11:39:57 -0700 (PDT) X-Received: by 10.107.13.204 with SMTP id 195mr8829271ion.89.1472150396826; Thu, 25 Aug 2016 11:39:56 -0700 (PDT) Original-Received: by 10.64.19.205 with HTTP; Thu, 25 Aug 2016 11:39:36 -0700 (PDT) In-Reply-To: <1472148645.17129.15.camel@bsdforen.de> X-Original-Sender: jyasskin@google.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@google.com; spf=pass (google.com: domain of jyasskin@google.com designates 2607:f8b0:4001:c0b::22a as permitted sender) smtp.mailfrom=jyasskin@google.com; dmarc=pass (p=REJECT dis=NONE) header.from=google.com X-Original-From: Jeffrey Yasskin 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:27949 Archived-At: --001a113fe54075d944053ae9b97a Content-Type: text/plain; charset=UTF-8 On Thu, Aug 25, 2016 at 11:10 AM, Dominic Fandrey wrote: > On Thu, 2016-08-25 at 16:55 +0100, D. B. wrote: > > On Thu, Aug 25, 2016 at 4:17 PM, Derek Ross > wrote: > > > > > > > > Note that enums can have duplicate values, which throws a wrench into > the > > > reflection works. E.g.: > > > > > > enum class FooBar { KEKS = 2, DOSE = 2 }; > > > > > > What will the result be for: > > > > > > FooBar fb = FooBar::KEKS; > > > cout << static_cast(fb) ; > > > > > that only "throws a wrench into the reflection works" as proposed by the > > OP, by no means generally. the WG proposal linked (A) would not support > > this because it is static and (B) has presumably already accounted for > such > > possibilities and effortlessly gets around them with compile-time > > wizardry... again, *presumably.* > > > > It's not really useful for what I'm doing if it's not runtime capable. > > For multiple mentions I'd just leave it implementation defined or > establish a simple first definition rule. > > I am assuming that in most cases overlapping definitions are aliases: > > enum class Flags { NONE = 0, COMPATIBLE = 1, COMPAT = 1, EXPERIMENTAL > = 2 }; > The static reflection proposal lets you iterate at compile time over all the enum values inside an enumeration, which lets you write a generic library function to do what you want. That function will have to pick an answer to FlagsString(1), and we're hoping that some libraries appear to show us some options before we put a choice into the standard library. Jeffrey -- 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 email 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/CANh-dXmhWtTBeEwBheNOApVwiCkMB6Hwqg8n%2Bxjt5aMvoW%2Bpbg%40mail.gmail.com. --001a113fe54075d944053ae9b97a Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
On T= hu, Aug 25, 2016 at 11:10 AM, Dominic Fandrey <kamikaz= e@bsdforen.de> wrote:
On Thu, 2016-08-25 at 16:55 +0100, D. B. wrote:
> On Thu, Aug 25, 2016 at 4:17 PM, Derek Ross <antiquarktv@gmail.com> wrote: >
> >
> > Note that enums can have duplicate values, which throws a wrench = into the
> > reflection works.=C2=A0=C2=A0E.g.:
> >
> > enum class FooBar { KEKS =3D 2, DOSE =3D 2 };
> >
> > What will the result be for:
> >
> > FooBar fb =3D FooBar::KEKS;
> > cout << static_cast<char const*>(fb) ;
> >
> that only "throws a wrench into the reflection works" as pro= posed by the
> OP, by no means generally. the WG proposal linked (A) would not suppor= t
> this because it is static and (B) has presumably already accounted for= such
> possibilities and effortlessly gets around them with compile-time
> wizardry... again, *presumably.*
>

It's not really useful for what I'm doing if it's not runtime c= apable.

For multiple mentions I'd just leave it implementation defined or
establish a simple first definition rule.

I am assuming that in most cases overlapping definitions are aliases:

=C2=A0 =C2=A0 enum class Flags { NONE =3D 0, COMPATIBLE =3D 1, COMPAT =3D 1= , EXPERIMENTAL =3D 2 };
=C2=A0=
The static reflection proposal lets you iterate at compile time = over all the enum values inside an enumeration, which lets you write a gene= ric library function to do what you want. That function will have to pick a= n answer to FlagsString(1), and we're hoping that some libraries appear= to show us some options before we put a choice into the standard library.<= /div>

Jeffrey

--
You received this message because you are subscribed to the Google Groups &= quot;ISO C++ Standard - Future Proposals" group.
To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+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/CANh-dXmhWtTB= eEwBheNOApVwiCkMB6Hwqg8n%2Bxjt5aMvoW%2Bpbg%40mail.gmail.com.
--001a113fe54075d944053ae9b97a-- .