220 27617 <7f85133e-f985-4f96-b550-42909016ce2b@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: tomalak@gmail.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Sort of "static assert" for coverage of enumerations within a switch Date: Thu, 4 Aug 2016 16:10:39 -0700 (PDT) Lines: 192 Approved: news@gmane.org Message-ID: <7f85133e-f985-4f96-b550-42909016ce2b@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_988_809003679.1470352239480" X-Trace: blaine.gmane.org 1470352247 31539 195.159.176.226 (4 Aug 2016 23:10:47 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 4 Aug 2016 23:10:47 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBD2MBSP3TQARB4EWR66QKGQEEAJ22BY@isocpp.org Fri Aug 05 01:10:42 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pf0-f199.google.com ([209.85.192.199]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1bVRmj-0007Vh-Ju for gclcip-std-proposals@m.gmane.org; Fri, 05 Aug 2016 01:10:41 +0200 Original-Received: by mail-pf0-f199.google.com with SMTP id w128sf484124304pfd.3 for ; Thu, 04 Aug 2016 16:10:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:message-id:subject:mime-version:x-original-sender :reply-to:precedence:mailing-list:list-id:x-spam-checked-in-group :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=0/k6+pAFMgLzQMydZfp4Hwy0PUm38qPjm2ifdAHDPzs=; b=lmlPWo+HbsxDiyfB1vJahP8PyHtDKCL8u3eRM873VomQB0mvqDKgL/Bp41jYlvdD53 RBdXn800hOSOPV/B7KKj2Ftk2/a8NbXbzUs8yWhmLdPQCbPv7mXZgXUncRsqoEX+Z659 3/oD3I8qsBSYTrAGh4I4unDuziOonadANQ+0xuho3SXs5bEw7XLPT1ClISKs2aCf/LpD 3htGdjJME6A6J4QJw6w/ake6yc8Galg/L7YbDs0T+EyyDpeTqa5CgV0hOvcRgc440ZQZ HaVcwJgYyDDOwac7nyDfbfkAxdPG529jUULfLE3GfFt48FB4Z7Pzplwv+RjjzuOOModN +ZAw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=date:from:to:message-id:subject:mime-version:x-original-sender :reply-to:precedence:mailing-list:list-id:x-spam-checked-in-group :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=0/k6+pAFMgLzQMydZfp4Hwy0PUm38qPjm2ifdAHDPzs=; b=ck0o5NCnxmeSpMJf2L3jlnoJRJ2UD2kDazOZLdx9EsGdmvtetF81dJTXYkd8CFqsyJ RpsYY9QvmW0jzgaIuQKmQ8wT+q+erwZRJfJzLW5Ud/kg6xjWrWh7aCzgaxOobRjYUAGm yeOQuWZjfqK6d4+giV0sn85s4Y/ybNNqlrO4TMSRB0H3AvLEhCckZzdYVW9H516cr0q1 anK2t20yGzpcnQV8CdyYXf4ZJShTYY3L3K63f7VSZXg+l/tAFcf+rSSMFd6ty26hLOfr TmeRdpDfe8MbWK6Ir99dAHcpCxU34r6Jn3AMR+5LX1Pc1gCi/8zh/w8T9z6qZ6NWcmmm 2+0A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to:message-id:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=0/k6+pAFMgLzQMydZfp4Hwy0PUm38qPjm2ifdAHDPzs=; b=epMTwiILtQNy9PkBbmY71/FGiYt0zPtHY01nAqJhoFWpWDJbDALqQaZhrYwmECByXK nUMM2hTt9lmh2q98YKYrQhRJ0rFeqc+jyb5+CCBW8vVYEQG0lPwYOOL5GMuqDLLqy7wK vTC3A2stAFhT2i3AcCHEV6QDZp8y0uSEX3n/X2OGOgwmkQWWx5pHCgvY3pqoxVgRlO8d cNa38AgJI6Q1qxj+DD7hhuoG41y3qKGxOS2HSHAiZE0vfjFxtDY6O34/V7zQ7VK8rNNC D85upHqn7s7SnJaGO5ECJnUk31sxyXBvHyPhfLtVCQJ8lph978jF4eLjLZnZcvfkCo8z ypag== X-Gm-Message-State: AEkoouvTHMuXM0AKoHw9uXzsShRioWBw7GbLdWJVKuQXxUjlDIOpImfYCvPPCNBoZfgVAw== X-Received: by 10.66.183.229 with SMTP id ep5mr65923056pac.3.1470352241330; Thu, 04 Aug 2016 16:10:41 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.20.68 with SMTP id 65ls1843411iou.16.gmail; Thu, 04 Aug 2016 16:10:40 -0700 (PDT) X-Received: by 10.36.36.10 with SMTP id f10mr26849ita.7.1470352240360; Thu, 04 Aug 2016 16:10:40 -0700 (PDT) X-Original-Sender: tomalak@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:27617 Archived-At: ------=_Part_988_809003679.1470352239480 Content-Type: multipart/alternative; boundary="----=_Part_989_1004757785.1470352239487" ------=_Part_989_1004757785.1470352239487 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sup, Sorry that this is so embryonic, but I wanted to open a discussion about it= =20 before going too far down the rabbit hole. Besides, it may have been=20 considered already. Good old fashioned enum: enum E { A, B, C }; Make it a scoped enum if you like. Two ways of "ensuring" that all enumerators are considered in a switch=20 (which isn't always what you want; let's assume that, in this scenario, it= =20 *is*): switch (e) { case A: case B: case C: foo(); break; =20 default: assert(false); } Or my favourite =E2=80=94 omit the `default` case and pay attention to warn= ings so=20 that you at least get immediate feedback at build time: switch (e) { case A: case B: case C: foo(); break; } Maybe we should have a sort of static_assert equivalent that can break the= =20 build when not all enumerations are covered by a switch? Just a thought. Discuss..... -Lightness --=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/7f85133e-f985-4f96-b550-42909016ce2b%40isocpp.or= g. ------=_Part_989_1004757785.1470352239487 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Sup,

Sorry that this is so embryonic, b= ut I wanted to open a discussion about it before going too far down the rab= bit hole. Besides, it may have been considered already.

= Good old fashioned enum:

enu= m E
{
=C2=A0 =C2=A0A,
=C2=A0 =C2=A0B,
=C2=A0 =C2=A0C
};


Make it a scoped enum if= you like.

Two ways of "ensuring" that a= ll enumerators are considered in a switch (which isn't always what you = want; let's assume that, in this scenario, it is):
switch (e) {
=C2=A0 =C2=A0= case A:
=C2=A0 =C2=A0case B:
=C2=A0 =C2=A0case C:
=C2=A0 =C2=A0 =C2=A0 foo();
=C2=A0 =C2=A0 =C2=A0 break;
=C2=A0 =C2=A0
=C2=A0 =C2=A0default:
=C2=A0 =C2=A0 =C2=A0 assert(false);
}


Or = my favourite =E2=80=94 omit the `default` case and pay attention to warning= s so that you at least get immediate feedback at build time:

switch (e) <= /span>{
=C2=A0 =C2=A0case A:
=C2=A0 =C2=A0case B:
=C2=A0 =C2=A0case C:
=C2=A0 =C2=A0 =C2=A0foo();
=C2=A0 =C2=A0 =C2=A0break;
}


=
Maybe we should have a sort of static_assert=C2=A0equivalent that can = break the build when not all enumerations are covered by a switch?

Just a thought.

Discuss.....


-Lightness

--
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/7f85133e-f985-4f96-b550-42909016ce2b= %40isocpp.org.
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