220 40116 article Path: news.gmane.org!.POSTED!not-for-mail From: Daniel Gutson Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: enumerator duplicated value attribute Date: Fri, 7 Sep 2018 15:55:42 -0300 Lines: 114 Approved: news@gmane.org Message-ID: Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="000000000000a28a7b05754c8e58" X-Trace: blaine.gmane.org 1536346431 6000 195.159.176.226 (7 Sep 2018 18:53:51 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 7 Sep 2018 18:53:51 +0000 (UTC) To: std-proposals Original-X-From: std-proposals+bncBDE3NBMV6UFBBO4TZPOAKGQELGWUFFY@isocpp.org Fri Sep 07 20:53:46 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-lf1-f72.google.com ([209.85.167.72]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fyLt4-0001TD-OQ for gclcip-std-proposals@m.gmane.org; Fri, 07 Sep 2018 20:53:46 +0200 Original-Received: by mail-lf1-f72.google.com with SMTP id o4-v6sf2850675lfg.11 for ; 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[209.85.220.41]) by mx.google.com with SMTPS id p64-v6sor4785575ljp.39.2018.09.07.11.55.55 for (Google Transport Security); Fri, 07 Sep 2018 11:55:55 -0700 (PDT) Received-SPF: pass (google.com: domain of danielgutson@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; X-Received: by 2002:a2e:870b:: with SMTP id m11-v6mr6205861lji.2.1536346554526; Fri, 07 Sep 2018 11:55:54 -0700 (PDT) X-Original-Sender: danielgutson@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=lLffIGD2; spf=pass (google.com: domain of danielgutson@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=danielgutson@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Spam-Checked-In-Group: std-proposals@isocpp.org 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:40116 Archived-At: --000000000000a28a7b05754c8e58 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hi, sometimes is important to prevent duplication of enumerators in the enumerations. That's why some compilers such as clang has the -Wduplicate-enum. However there are cases such as ranges within enums, where enumerators define a category and then are followed by the first element of the category, with the same value. enum Ranges { CategoryX =3D 100, X1 =3D CategoryX, X2, X3 CategoryY =3D 200 // ... }; In order to allow such cases coexist with the useful diagnostic, I propose adding an enumerator attribute, such as [[allow_duplicate]] enum Ranges { CategoryX =3D 100 [[allow_duplicate]], X1 =3D CategoryX, X2, X3 CategoryY =3D 200 [[allow_duplicate]] // ... }; This way, we can have the diagnostic and also explicit the intention that in those cases it is OK to have a repeated value. Comments? Daniel. --=20 Who=E2=80=99s got the sweetest disposition? One guess, that=E2=80=99s who? Who=E2=80=99d never, ever start an argument? Who never shows a bit of temperament? Who's never wrong but always right? Who'd never dream of starting a fight? Who get stuck with all the bad luck? --=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/CAFdMc-39pqfHATmWOA%3DiVNPmGDW0yqGh-jtqrxQPb9ALA= %3DNK2A%40mail.gmail.com. --000000000000a28a7b05754c8e58 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Hi,

=C2=A0 =C2=A0sometimes is important= to prevent duplication of enumerators in the enumerations. That's why = some compilers such as clang has the -Wduplicate-enum.
However th= ere are cases such as ranges within enums, where enumerators define a categ= ory and then are followed by the first element of the category, with the sa= me value.

enum Ranges
{
=C2=A0= =C2=A0 CategoryX =3D 100,
=C2=A0 =C2=A0 =C2=A0 =C2=A0X1 =3D Cate= goryX,
=C2=A0 =C2=A0 =C2=A0 =C2=A0X2,
=C2=A0 =C2=A0 =C2= =A0 =C2=A0X3
=C2=A0 =C2=A0 =C2=A0CategoryY =3D 200
=C2= =A0 =C2=A0 =C2=A0 =C2=A0// ...
};

In ord= er to allow such cases coexist with the useful diagnostic, I propose adding= an enumerator attribute, such as [[allow_duplicate]]

<= div>
enum Ranges
{
=C2=A0 =C2=A0 CategoryX =3D 100 = [[allow_duplicate]],
=C2=A0 =C2=A0 =C2=A0 =C2=A0X1 =3D CategoryX,=
=C2=A0 =C2=A0 =C2=A0 =C2=A0X2,
=C2=A0 =C2=A0 =C2=A0 = =C2=A0X3
=C2=A0 =C2=A0 =C2=A0CategoryY =3D 200 [[allow_duplicate]= ]
=C2=A0 =C2=A0 =C2=A0 =C2=A0// ...
};

This way, we can have the diagnostic and also explicit the intenti= on that in those cases it is OK to have a repeated value.

Comments?

=C2=A0 =C2=A0 Daniel.


=
--
Who=E2=80=99s got the sweetest disposition?
One gue= ss, that=E2=80=99s who?
Who=E2=80=99d never, ever start an argument?
= Who never shows a bit of temperament?
Who's never wrong but always r= ight?
Who'd never dream of starting a fight?
Who get stuck with a= ll the bad luck?

--
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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/CAFdMc-39pqfH= ATmWOA%3DiVNPmGDW0yqGh-jtqrxQPb9ALA%3DNK2A%40mail.gmail.com.
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