220 33770 article Path: news.gmane.org!.POSTED!not-for-mail From: Tony V E Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: A more advanced switch Date: Wed, 9 Aug 2017 22:45:24 -0400 Lines: 192 Approved: news@gmane.org Message-ID: References: <574320af-c1ae-4676-883c-ae4e91fcd874@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="001a113d3aac4008d805565d3086" X-Trace: blaine.gmane.org 1502333129 30143 195.159.176.226 (10 Aug 2017 02:45:29 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 10 Aug 2017 02:45:29 +0000 (UTC) To: Standard Proposals Original-X-From: std-proposals+bncBCUZ5QWKNQIMLENPZQCRUBHFEPH7Y@isocpp.org Thu Aug 10 04:45:22 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pg0-f71.google.com ([74.125.83.71]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dfdTM-0007NM-RB for gclcip-std-proposals@m.gmane.org; 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[2607:f8b0:400d:c0d::232]) by mx.google.com with ESMTPS id s3si4482493qtg.497.2017.08.09.19.45.25 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 09 Aug 2017 19:45:25 -0700 (PDT) Received-SPF: pass (google.com: domain of tvaneerd@gmail.com designates 2607:f8b0:400d:c0d::232 as permitted sender) client-ip=2607:f8b0:400d:c0d::232; Original-Received: by mail-qt0-x232.google.com with SMTP id t37so46965855qtg.5 for ; Wed, 09 Aug 2017 19:45:25 -0700 (PDT) X-Received: by 10.237.36.38 with SMTP id r35mr14707898qtc.327.1502333125001; Wed, 09 Aug 2017 19:45:25 -0700 (PDT) Original-Received: by 10.237.42.10 with HTTP; Wed, 9 Aug 2017 19:45:24 -0700 (PDT) In-Reply-To: X-Original-Sender: tvaneerd@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=vgNwZED8; spf=pass (google.com: domain of tvaneerd@gmail.com designates 2607:f8b0:400d:c0d::232 as permitted sender) smtp.mailfrom=tvaneerd@gmail.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=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:33770 Archived-At: --001a113d3aac4008d805565d3086 Content-Type: text/plain; charset="UTF-8" On Wed, Aug 9, 2017 at 10:23 PM, Bo Persson wrote: > On 2017-08-10 03:13, gmisocpp@gmail.com wrote: > >> >> >> On Thursday, August 10, 2017 at 5:08:18 AM UTC+12, Tony V E wrote: >> >> break by default is fine, how do I opt-out within switch break, or >> is it all or nothing? >> >> switch break(x) >> { >> case 1: >> case 2: >> foo(); >> case 3: >> bar(); >> case 4: >> etc(); >> } >> >> >> How do I get fallthru on case 1 to 2? >> >> >> I would not object to fallthrough being a keyword like so (but see later): >> >> switch break(x) >> { >> case 1: fallthrough; >> case 2: >> foo(); >> case 3: >> bar(); >> case 4: >> etc(); >> } >> >> > That would make it really experts-only, as we already have the current > version > > switch (x) > { > case 1: [[fallthrough]]; > case 2: > foo(); > case 3: > bar(); > case 4: > etc(); > } > > > How many variations do we need? > > > Bo Persson > > Well, the [[fallthrough]] one, in some sense, doesn't really exist, because attributes are ignorable and don't change anything. I don't expect to ever get "switch break (x)", but I do expect we eventually get pattern matching that subsumes switch. Maybe "switch [x]", since square brackets are in style? Or throw in an auto or something. Or it is called "inspect" (that's the name Bjarne used). When we do get "inspect", it we almost certainly break by default. I think we will still _probably_ need something to do fallthrough - and it can't be an attribute. Or maybe we say fallthrough really isn't worth it. -- Be seeing you, Tony -- 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/CAOHCbisUO1-rHoSrFK-qc76OFxPsVx3NJOnyV6vb1WFDcwQ-NA%40mail.gmail.com. --001a113d3aac4008d805565d3086 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


On Wed, Aug 9, 2017 at 10:23 PM, Bo Persson <bop@gmb.dk> wrote:=
On 2017-08-10 03:13, gmisocpp@gmail.com wrote:


On Thursday, August 10, 2017 at 5:08:18 AM UTC+12, Tony V E wrote:

=C2=A0 =C2=A0 break by default is fine, how do I opt-out within switch brea= k, or
=C2=A0 =C2=A0 is it all or nothing?

=C2=A0 =C2=A0 switch break(x)
=C2=A0 =C2=A0 {
=C2=A0 =C2=A0 case 1:
=C2=A0 =C2=A0 case 2:
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0foo();
=C2=A0 =C2=A0 case 3:
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0bar();
=C2=A0 =C2=A0 case 4:
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0etc();
=C2=A0 =C2=A0 =C2=A0 }


=C2=A0 =C2=A0 How do I get fallthru on case 1 to 2?


I would not object to fallthrough being a keyword like so (but see later):<= br>
switch break(x)
{
case 1: fallthrough;
case 2:
=C2=A0 =C2=A0 =C2=A0foo();
case 3:
=C2=A0 =C2=A0 =C2=A0bar();
case 4:
=C2=A0 =C2=A0 =C2=A0etc();
=C2=A0 }


 That would make it really experts-only, as we already have the current vers= ion

switch (x)
{
case 1: [[fallthrough]];
case 2:
=C2=A0 =C2=A0 =C2=A0foo();
case 3:
=C2=A0 =C2=A0 =C2=A0bar();
case 4:
=C2=A0 =C2=A0 =C2=A0etc();
=C2=A0 }


 How many variations do we need?


=C2=A0 =C2=A0 Bo Persson


Well, the [[fallthrough]] one, = in some sense, doesn't really exist, because attributes are ignorable a= nd don't change anything.

I don't expect to ever = get "switch break (x)", but I do expect we eventually get pattern= matching that subsumes switch.=C2=A0 Maybe "switch [x]", since s= quare brackets are in style? Or throw in an auto or something.=C2=A0 Or it = is called "inspect" (that's the name Bjarne used).

When we do get "inspect", it we almost certainly break by= default.=C2=A0 I think we will still _probably_ need something to do fallt= hrough - and it can't be an attribute.
Or maybe we say fa= llthrough really isn't worth it.


--
Be seeing you,
Tony

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