220 27959 <1472202710.17129.25.camel@bsdforen.de> article Path: news.gmane.org!.POSTED!not-for-mail From: Dominic Fandrey Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Make (strongly typed) enums castable to char const * const Date: Fri, 26 Aug 2016 11:11:50 +0200 Lines: 83 Approved: news@gmane.org Message-ID: <1472202710.17129.25.camel@bsdforen.de> 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: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1472202720 26512 195.159.176.226 (26 Aug 2016 09:12:00 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 26 Aug 2016 09:12:00 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCPM3OG72QHBBWMPQC7AKGQE4JECEQY@isocpp.org Fri Aug 26 11:11:55 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-lf0-f69.google.com ([209.85.215.69]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1bdDB3-0006R7-Gx for gclcip-std-proposals@m.gmane.org; Fri, 26 Aug 2016 11:11:53 +0200 Original-Received: by mail-lf0-f69.google.com with SMTP id k135sf48659576lfb.2 for ; Fri, 26 Aug 2016 02:11:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=message-id:subject:from:to:date:in-reply-to:references:mime-version :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=XkUJSZxINNrqD3JDQrBF4at8/hqHINF8l37Yzd9PC6Q=; b=h9zeZP6e2BSuFZw0tHGhi+QAltspcUoRXFyBnK737zWhIjPXIIXGsYcV11HP937goS wvRrKgns8O4SQ+MkfcAja94XjSLL62ranOrqzEj4PFNwytPqZr4awqdb53l0oUEE4non fJ/8iwROwGDylKe7Rr1LAl8Il94VtLLxMeGJtGnkNIqxLnAvl5ogi1r6rZJ/7viQN3DQ 0Kzq/+JQzCqt9dOjCd6ex3PZUeXu+d5U2Qgd4jvTz+iP+lTGlbbQGPOq3zroI/XmKteH cWBWvx8XP7oPqB3lDnPHCYnyNYxRq2Js7hSQBu2EhM6+3J4xdSvr5yczFQT2mUGa+231 es8g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:message-id:subject:from:to:date:in-reply-to :references:mime-version: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=XkUJSZxINNrqD3JDQrBF4at8/hqHINF8l37Yzd9PC6Q=; b=VElnn0L/54tu+RTkY1nSfae+dYJCGpccmrsPl2O9oYV6oZtKR1qKHfWoJoGMsjugQ8 z7PBhW8LAP/GB7zipvjN+coChzo6XXD7WmEmwMiehG0/aqGqfLdZIVjkcyhf5Cuaja7l FosSWl1E+l5khtCEXK7zPU+7PfL7A6nfnixJ8NCPly1eXkrvexT26+xtZQtdFgylSQBY EtyAy9d8i4shkw8PrgmncF6pZgjNXOP6QZKkDSk94RD4LThz+vhquCdZIYzJ5hYX4DFa 3A/sl4xCLRf/Kg33lPLg0XiY3xc+lxorpdHuzNaadoLQqoSbBQOFrOGKzVq71ndDoM0b Wrt X-Gm-Message-State: AE9vXwN4s1SWH0dA9EryTKAXBDheIIyTWDx/vryL6ywkmNI7qlzmiGSiAhzeMrpKHOiUUA== X-Received: by 10.28.199.6 with SMTP id x6mr389933wmf.2.1472202714557; Fri, 26 Aug 2016 02:11:54 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.46.5.22 with SMTP id 22ls162017ljf.36.gmail; Fri, 26 Aug 2016 02:11:52 -0700 (PDT) X-Received: by 10.25.205.200 with SMTP id d191mr679213lfg.212.1472202712818; Fri, 26 Aug 2016 02:11:52 -0700 (PDT) Original-Received: from bsdforen.de (bsdforen.de. [82.193.243.81]) by mx.google.com with ESMTP id r192si8034018lfr.2.2016.08.26.02.11.52 for ; Fri, 26 Aug 2016 02:11:52 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of kamikaze@bsdforen.de designates 82.193.243.81 as permitted sender) client-ip=82.193.243.81; Original-Received: from localhost (iz-aix-213a.HS-Karlsruhe.DE [193.196.64.213]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by bsdforen.de (Postfix) with ESMTPSA id 0F93E3989FA for ; Fri, 26 Aug 2016 11:11:50 +0200 (CEST) In-Reply-To: X-Mailer: Evolution 3.18.5.1 FreeBSD GNOME Team Port X-Original-Sender: kamikaze@bsdforen.de X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of kamikaze@bsdforen.de designates 82.193.243.81 as permitted sender) smtp.mailfrom=kamikaze@bsdforen.de 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:27959 Archived-At: On Thu, 2016-08-25 at 11:39 -0700, 'Jeffrey Yasskin' via ISO C++ Standard -= Future Proposals wrote: > On Thu, Aug 25, 2016 at 11:10 AM, Dominic Fandrey > wrote: >=20 > >=20 > > On Thu, 2016-08-25 at 16:55 +0100, D. B. wrote: > > >=20 > > > On Thu, Aug 25, 2016 at 4:17 PM, Derek Ross > > wrote: > > >=20 > > >=20 > > > >=20 > > > >=20 > > > > Note that enums can have duplicate values, which throws a wrench in= to > > the > > >=20 > > > >=20 > > > > reflection works.=C2=A0=C2=A0E.g.: > > > >=20 > > > > enum class FooBar { KEKS =3D 2, DOSE =3D 2 }; > > > >=20 > > > > What will the result be for: > > > >=20 > > > > FooBar fb =3D FooBar::KEKS; > > > > cout << static_cast(fb) ; > > > >=20 > > > 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 suppo= rt > > > this because it is static and (B) has presumably already accounted fo= r > > such > > >=20 > > > possibilities and effortlessly gets around them with compile-time > > > wizardry... again, *presumably.* > > >=20 > > It's not really useful for what I'm doing if it's not runtime capable. > >=20 > > For multiple mentions I'd just leave it implementation defined or > > establish a simple first definition rule. > >=20 > > I am assuming that in most cases overlapping definitions are aliases: > >=20 > > =C2=A0=C2=A0=C2=A0=C2=A0enum class Flags { NONE =3D 0, COMPATIBLE =3D 1= , COMPAT =3D 1, EXPERIMENTAL > > =3D 2 }; > >=20 > 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. That sounds fine to me, I prefer a generic approach over my limited proposal. I guess it wouldn't be too difficult to build a nested type containing the string and the enum value and a constexpr function template that iterates through the type and returns the string for the first enum match. You could also build one that would return "COMPATIBLE|EXPERIMENTAL" for Flags{3}, for enums that only have powers of two values. But that would probably result in the creation in n! strings, so it might not be a great idea (even if n is usually limited to 64). --=20 A: Because it fouls the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing on usenet and in e-mail? --=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/1472202710.17129.25.camel%40bsdforen.de. .