220 31933 <5d35116c-5974-417a-840f-3dc714eae601@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Nicol Bolas Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: This variable should not be named: an identifier (not) to remember Date: Sun, 2 Apr 2017 15:45:49 -0700 (PDT) Lines: 165 Approved: news@gmane.org Message-ID: <5d35116c-5974-417a-840f-3dc714eae601@isocpp.org> References: <985b9b2a-c734-45eb-95f4-db4dc0d309a1@isocpp.org> <1491170458.9U0G8TLsOk@tjmaciei-mobl1> <10c2c556-b6bb-4714-83bc-7b0ac8fd4143@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_3712_144089446.1491173149922" X-Trace: blaine.gmane.org 1491173155 15206 195.159.176.226 (2 Apr 2017 22:45:55 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 2 Apr 2017 22:45:55 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCEKFTV6ZUMBBHX6QXDQKGQEU2WDDOA@isocpp.org Mon Apr 03 00:45:51 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-oi0-f72.google.com ([209.85.218.72]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cuoFl-0002tU-TM for gclcip-std-proposals@m.gmane.org; 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Sun, 02 Apr 2017 15:45:51 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.47.171 with SMTP id r40ls6498951otb.0.gmail; Sun, 02 Apr 2017 15:45:50 -0700 (PDT) X-Received: by 10.157.84.22 with SMTP id j22mr643593oth.13.1491173150560; Sun, 02 Apr 2017 15:45:50 -0700 (PDT) In-Reply-To: X-Original-Sender: jmckesson@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:31933 Archived-At: ------=_Part_3712_144089446.1491173149922 Content-Type: multipart/alternative; boundary="----=_Part_3713_2138178914.1491173149922" ------=_Part_3713_2138178914.1491173149922 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Sunday, April 2, 2017 at 4:13:36 PM UTC-4, Richard Smith wrote: > > On 2 April 2017 at 12:45, Nicol Bolas >= =20 > wrote: > >> On Sunday, April 2, 2017 at 3:28:54 PM UTC-4, Richard Smith wrote: >>> >>> On 2 April 2017 at 11:03, Thiago Macieira wrote: >>> >>>> On s=C3=A1bado, 1 de abril de 2017 21:19:37 PDT Richard Smith wrote: >>>> > Have you considered that possibility? It would give a better name (_= =20 >>>> rather >>>> > than __) and avoid "breaking" existing code that uses __. >>>> >>>> _ is not reserved to the compiler and is VERY often #defined to gettex= t. >>>> >>> >>> Only as a function-like macro. >>> >>> Let's use __. >>> >>> >>> Let's use the thing that works best for C++, sure. I am not (yet)=20 >>> convinced that's __. >>> >> >> Well, let's look at the options. >> >> You can't use nothing; that would create parsing ambiguities. So you hav= e=20 >> to put something there: either an identifier or something that is not an= =20 >> identifier. >> >> If it is not an identifier, then it must be a keyword (new or old) or=20 >> some form of punctuation. Adding a new keyword for something like this i= s=20 >> rather silly. And I don't know of an old keyword that would make for a g= ood=20 >> placeholder. >> >> You could use `[]` as I once suggested, piggybacking off of structured= =20 >> binding rules. But most other punctuation would be confusing or otherwis= e=20 >> unexpected in a variable declaration. >> >> If it is an identifier, then it must be a *reserved* identifier, to=20 >> minimize code breakage when we change its meaning. >> > > As I pointed out, this is an incorrect conclusion. There is no necessity= =20 > for any code breakage here, and there is no need to pick a reserved=20 > identifier: the core functionality of this proposal does not require that= =20 > the identifier be unusable within its scope, and if we don't add that=20 > restriction, this is strictly an extension. > But that makes it a *different proposal*. This proposal is about having a= =20 scope-bound object which *cannot be later referenced*, which has a name=20 that is generated by the compiler. That's what the proposal is for: "for=20 all variables whose name is not important and that is no longer needed=20 after declaration". You are talking about something else. --=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/5d35116c-5974-417a-840f-3dc714eae601%40isocpp.or= g. ------=_Part_3713_2138178914.1491173149922 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
On Sunday, April 2, 2017 at 4:13:36 PM UTC-4, Richard Smit= h wrote:
=
On 2 April 2017 at 12:45, Nicol Bolas <jmck...@gmail.com> wrote:
On Sunday, April 2, 2017 at 3:28:54 PM UTC-4, Richa= rd Smith wrote:
On 2 April 2017 at 11:03, Thiago Macieir= a <thi...@macieira.org> wrote:
On s=C3=A1bado, 1 de abr= il de 2017 21:19:37 PDT Richard Smith wrote:
> Have you considered that possibility? It would give a better name (_ r= ather
> than __) and avoid "breaking" existing code that uses __.
_ is not reserved to the compiler and is VERY often #defined to gett= ext.

Only as a function-like macro.

Let's use __.

Let's use the thing t= hat works best for C++, sure. I am not (yet) convinced that's __.
=

Well, let's look at the = options.

You can't use nothing; that would create parsing ambigu= ities. So you have to put something there: either an identifier or somethin= g that is not an identifier.

If it is not an identifier, then it mus= t be a keyword (new or old) or some form of punctuation. Adding a new keywo= rd for something like this is rather silly. And I don't know of an old = keyword that would make for a good placeholder.

You could use `[]` a= s I once suggested, piggybacking off of structured binding rules. But most = other punctuation would be confusing or otherwise unexpected in a variable = declaration.

If it is an identifier, then it must be a reserved identifier, to minimize code breakage when we change its meaning.
<= /div>

As I pointed out, this is an incorrec= t conclusion. There is no necessity for any code breakage here, and there i= s no need to pick a reserved identifier: the core functionality of this pro= posal does not require that the identifier be unusable within its scope, an= d if we don't add that restriction, this is strictly an extension.

But that makes it a different p= roposal. This proposal is about having a scope-bound object which ca= nnot be later referenced, which has a name that is generated by the com= piler. That's what the proposal is for: "for all variables whose n= ame is not important and that is no longer needed after declaration".<= br>
You are talking about something else.

--
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/5d35116c-5974-417a-840f-3dc714eae601= %40isocpp.org.
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