220 986 article Path: news.gmane.org!not-for-mail From: Arthur Tchaikovsky Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Allow multiple same case values if they are next to each other Date: Wed, 12 Dec 2012 03:27:41 -0800 (PST) Lines: 137 Approved: news@gmane.org Message-ID: References: <8d87c9d3-a192-45aa-98a6-d8c727f18a46@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_123_24783969.1355311661657" X-Trace: ger.gmane.org 1355311665 22794 80.91.229.3 (12 Dec 2012 11:27:45 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 12 Dec 2012 11:27:45 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDL6FI4NYYERBL6UUGDAKGQEX5DUQCA@isocpp.org Wed Dec 12 12:27:59 2012 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-vc0-f200.google.com ([209.85.220.200]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1TikTl-0007sE-EJ for gclcip-std-proposals@m.gmane.org; Wed, 12 Dec 2012 12:27:57 +0100 Original-Received: by mail-vc0-f200.google.com with SMTP id f13sf834393vcb.7 for ; Wed, 12 Dec 2012 03:27:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=x-beenthere:date:from:to:message-id:in-reply-to:references:subject :mime-version:x-original-sender:reply-to:precedence:mailing-list :list-id:x-google-group-id:list-post:list-help:list-archive :list-subscribe:list-unsubscribe:content-type; bh=eKZa3utHcwlWKwCfuK32RaF1vXdF7lSYIqIQtmERaHs=; b=DHdAGX/6D7oMv7aPnGr/09JHx5umY5Dipyx2XLMDgUgtW+PGFHUvRD4fBNeGPdylYg Zn1GwXWFaGZqKC5aY/7Ncx+QIYKOHvvXBret1QF/tZUZ4PLiCclt0nceTrHlrANZ044M m2mCNXvwbhQqmkv1YsRXzwPq2nlvSMPllfc9qg+uVLdhLaHcjfFhfeq+iP52S4Ig9ujN UivSwWKo7hYaSAf0ojoU8kdY6clQBTiVipNXBn1Ib3AU8iFE0G/2nHY0PgZVUBixyKwX nw5HXYTJ3XxcRnkMDD2FlqLuviRJuIMuq2/PPBe/CcahDx0OXXbWIHngsPLUHGxLUhVk 9Hww== Original-Received: by 10.236.117.66 with SMTP id i42mr928269yhh.8.1355311663242; Wed, 12 Dec 2012 03:27:43 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.117.167 with SMTP id kf7ls1056437qeb.40.gmail; Wed, 12 Dec 2012 03:27:42 -0800 (PST) Original-Received: by 10.49.87.1 with SMTP id t1mr234764qez.41.1355311662302; Wed, 12 Dec 2012 03:27:42 -0800 (PST) In-Reply-To: <8d87c9d3-a192-45aa-98a6-d8c727f18a46@isocpp.org> X-Original-Sender: atch.cpp@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:986 Archived-At: ------=_Part_123_24783969.1355311661657 Content-Type: text/plain; charset=ISO-8859-1 I agree with you, and think that this should be amended. After all we have 'case' not 'value' in switch statement. So different cases should be allowed independently of their values. On Tuesday, 11 December 2012 23:24:38 UTC, Johannes Schaub wrote: > Here is a simple proposal for allowing multiple consecutive identical case > values. My use-case were buttons that have a left and a right label, with > each label having their own led (but the button was a single button sending > a single key id). > > I had this code > > enum Key { > Key_7 = 1 > Key_Current = 1, > > Key_8 = 2, > Key_Voltage = 2, > > // ... > }; > > Pair getLeds(Key key) { > switch(key) { > case Key_7: > case Key_Current: > // ... > break; > > case Key_8: > case Key_Voltage: > // ... > break; > } > } > > C++ does't like this. It would be nice if this was allowed. I wrote an > ugly workaround like > > Pair getLeds(Key key) { > switch(key) { > case SameValues::value: > // ... > break; > > case SameValues::value: > // ... > break; > } > } > > Which static_asserts that all constants have the same value. But I would > like to have native readable language support. Does anyone feel the same? > -- ------=_Part_123_24783969.1355311661657 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
I agree with you, and think that this should be amended. After all we = have 'case' not 'value' in switch statement. So different cases should be a= llowed independently of their values.

On Tuesday, 11 December 2012 23:24:38 UTC, Johannes Schaub wrote:<= /DIV>
Here is a simple proposal for allo= wing multiple consecutive identical case values. My use-case were buttons t= hat have a left and a right label, with each label having their own led (bu= t the button was a single button sending a single key id). =20

I had this code

    enum Key {
      Key_7 =3D 1
      Key_Current =3D 1,

      Key_8 =3D 2,
      Key_Voltage =3D 2, 

      // ...
    };

    Pair<LedNumer, LedNumber> getLeds(Key key) {
      switch(key) {
        case Key_7:
        case Key_Current:
          // ...
          break;

        case Key_8: 
        case Key_Voltage:
          // ...
          break;
      }
    }

C++ does't like this. It would be nice if this was allowed. I wrote an= ugly workaround like

    Pair<LedNumer, LedNumber> getLeds(Key key) {
      switch(key) {
        case SameValues<Key_7, Key_Current>:= :value:
          // ...
          break;

        case SameValues<Key_8, Key_Voltage>:= :value:
          // ...
          break;
      }
    }

Which static_asserts that all constants have the same value. But I wou= ld like to have native readable language support. Does anyone feel the same= ?

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