220 31893 <7a03017c-ad72-466f-b2a3-c07f9186f387@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: raffaele.rossi@mavensecurities.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: This variable should not be named: an identifier (not) to remember Date: Thu, 30 Mar 2017 01:08:48 -0700 (PDT) Lines: 189 Approved: news@gmane.org Message-ID: <7a03017c-ad72-466f-b2a3-c07f9186f387@isocpp.org> References: <985b9b2a-c734-45eb-95f4-db4dc0d309a1@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_2303_1455096496.1490861328795" X-Trace: blaine.gmane.org 1490861341 28665 195.159.176.226 (30 Mar 2017 08:09:01 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 30 Mar 2017 08:09:01 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBC4237OVUEPRBEP26LDAKGQEZAJPMPI@isocpp.org Thu Mar 30 10:08:51 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-it0-f69.google.com ([209.85.214.69]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1ctV8O-0005SP-MI for gclcip-std-proposals@m.gmane.org; Thu, 30 Mar 2017 10:08:44 +0200 Original-Received: by mail-it0-f69.google.com with SMTP id 19sf2456075itj.1 for ; Thu, 30 Mar 2017 01:08:50 -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:in-reply-to:references: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=nhqGFCfmValLbGC80dGJmk5ZVLhDwR+S/bOHr7scXwM=; b=aw3PTPziutoRm3TRVw0r7k0ucM0z5reETVCPc+w+8ddfys4PtCCbvygb3Hjv1efeOt EgIc6UugMr8CYknzHHDXmTGq1Pd9gXuGA2ultfnktsARFtkKv1GR7fgQ6bCz0vwQlbY4 Fq+Nh3xvOgYcza8GSBsHNSWrNtCAVrHbfxBv4HatzFUOH5ddPTc474rLellP86Y4vS4o EvrID/8ga9Fu9ZHySTMUeUS7fMdpPH4O+xVDwGjJy1gqEDMSmwuAOpJr443xa3s1DqTV ydUpBKcRQt23YVy8rVTy/2ro+he705BkRCpwX2nFd1SU5SNxlgOu9JIA2I1OQgv2KIUb ydmg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:message-id:in-reply-to:references :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=nhqGFCfmValLbGC80dGJmk5ZVLhDwR+S/bOHr7scXwM=; b=qxW99ShPI+iwf+MbneLNldjy4zlwRd6dUAccunCm19EgGyRBkk9KeO/TPz5md/laQ3 mz1b7n7oQaSQq6rjNgzftJ1jYyqDpfIk95VbKuWDAFB2w+5eNyarqeqD4Rrap3e2YjjN heVkA6/eIhyKT/e/F8QKBxmof1zt/8niUxiDr+9K3K+zAPVDLPrI584/39yLv7D2QOYo P3IM8sJuhMM0PS/hkux/InJUds3nPUmLkFQrVDRxXVFxySHlZpITn8wxnbI19o6SWdaH xagquBHJh09TRWVNMFVFBxBFJzTlTCZICXjgBBzApnzNtKFTgiw+3ynmmXITHxneFHEH xuZA== X-Gm-Message-State: AFeK/H3Nlttf2S/94wNdzW6fqp5AMf9eKubJ631D/aJUerCytO0yg2lqft3ujLhTNTSsnA== X-Received: by 10.107.13.20 with SMTP id 20mr1692300ion.1.1490861330298; Thu, 30 Mar 2017 01:08:50 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.24.83 with SMTP id t19ls2315823ott.28.gmail; Thu, 30 Mar 2017 01:08:49 -0700 (PDT) X-Received: by 10.157.13.75 with SMTP id 69mr567374oti.3.1490861329439; Thu, 30 Mar 2017 01:08:49 -0700 (PDT) In-Reply-To: <985b9b2a-c734-45eb-95f4-db4dc0d309a1@isocpp.org> X-Original-Sender: raffaele.rossi@mavensecurities.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:31893 Archived-At: ------=_Part_2303_1455096496.1490861328795 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Wouldn't it be much better to have a concept of *Context*? I am taking=20 inspiration from python (I know they use it for RAII, but that is a=20 different discussion). The code might look like: void foo() { // do stuff with (unique_lock{mutex}) { // critical code } // other stuff } Then, for prettiness and to avoid unnecessary indentations, when the=20 *Context* extends till the end of the parent scope, it can just be a=20 declaration: void foo() { with unique_lock{mutex}; // critical code } You can also nest *Contexts*: void foo() { with unique_lock{mutex1}; with unique_lock{mutex2}; // etc } Also, by having a proper concept of *Context*, compilers and static=20 analysis tools would have more information available. I don't know about the decomposition side of things, but perhaps using, say= =20 @ instead? But I have to admit I still haven't understood the difference= =20 with std::ignore (perhaps I have homework to do): auto [x, @, z] =3D expr; Is anything of this any useful at all? On Monday, 27 March 2017 21:27:11 UTC+1, Alberto Barbati wrote: > Hello, > > this is a draft for a proposal to add a special meaning to the identifier= =20 > __ (double underscore) so that it can be used (even repeatedly in the sam= e=20 > lexical scope) for all variables whose name is not important and that is = no=20 > longer needed after declaration. The draft includes a few examples. > > Is there any interest in this? > > Thanks in advance, > > Alberto > > --=20 This e-mail together with any attachments (the "Message") is confidential= =20 and may contain privileged information. If you are not the intended=20 recipient or if you have received this e-mail in error, please notify the= =20 sender immediately and permanently delete this Message from your system.=20 Do not copy, disclose or distribute the information contained in this=20 Message. Maven Investment Partners Ltd (No. 07511928), Maven Derivatives Ltd (No.=20 07511840) , MVN Asset Management Limited (No. 09659116), Maven Europe Ltd= =20 (No. 08966593), Maven Derivatives Asia Limited (No.10361312) & Maven=20 Securities Holding Ltd (No. 07505438) are registered as companies in=20 England and Wales and their registered address is Level 3, 6 Bevis Marks,= =20 London EC3A 7BA, United Kingdom. The companies=E2=80=99 VAT No. is 13553901= 6. Maven=20 Asia (Hong Kong) Ltd (No. 2444041) is registered in Hong Kong and its=20 registered address is 20/F, 198 Wellington St, Hong Kong. Only Maven=20 Derivatives Ltd and MVN Asset Management Limited are authorised and=20 regulated by the Financial Conduct Authority (Maven Derivatives Ltd FRN:=20 607267, MVN Asset Management Limited FRN: 714429) --=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/7a03017c-ad72-466f-b2a3-c07f9186f387%40isocpp.or= g. ------=_Part_2303_1455096496.1490861328795 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Wouldn't it be much better to have a concept of <= b>Context? I am taking inspiration from python (I know they use it for = RAII, but that is a different discussion).

The cod= e might look like:

=C2=A0 void foo() {
=C2=A0 =C2=A0 // do stuff
=C2=A0 =C2=A0 with (unique_lock{mutex}) {
=C2=A0 =C2=A0 =C2=A0 // critical code
=C2=A0 =C2=A0 }=
=C2=A0 =C2=A0 // other stu= ff
=C2=A0 }

Then, for prettiness and to avoid unnecessary inden= tations, when the Context extends till the end of the parent scope, = it can just be a declaration:

=C2=A0 void foo() {
=C2=A0 =C2=A0 with unique_lock{mutex};
<= font face=3D"courier new, monospace">=C2=A0 =C2=A0 // critical code
=C2=A0 }

You can also nest Contexts:

=C2=A0 void foo() {
=C2=A0 =C2=A0 with unique_loc= k{mutex1};
=C2= =A0 =C2=A0 with unique_lock{mutex2};
=C2=A0 =C2=A0 // etc
=C2=A0 }

Also, by having = a proper concept of Context, compilers and static analysis tools wou= ld have more information available.

I don't kn= ow about the decomposition side of things, but perhaps using, say @ =C2=A0instead? But I have to admit I = still haven't understood the difference with std::ignore (perhaps I have homework to do):
<= br>
=C2=A0 =C2=A0 auto [x, = @, z] =3D expr;

Is anything of this any= useful at all?

On Monday, 27 March 2017 21:27:11 = UTC+1, Alberto Barbati wrote:
Hello,

this is a draft for a proposal to = add a special meaning to the identifier __ (double underscore) so that it c= an be used (even repeatedly in the same lexical scope) for all variables wh= ose name is not important and that is no longer needed after declaration. T= he draft includes a few examples.

Is there any interest in this?
=
Thanks in advance,

Alberto


This e-mai= l together with any attachments (the "Message") is confidential a= nd may contain privileged information. If you are not the intended recipien= t or if you have received this e-mail in error, please notify the sender im= mediately and permanently delete this Message from your system. =C2=A0Do no= t copy, disclose or distribute the information contained in this Message.

Maven Investment Partners Ltd (No. 07511928), Maven Deri= vatives Ltd (No. 07511840) , MVN Asset Management Limited (No. 09659116), M= aven Europe Ltd (No. 08966593), Maven Derivatives Asia Limited (No.10361312= ) & Maven Securities Holding Ltd (No. 07505438) are registered as compa= nies in England and Wales and their registered address is Level 3, 6 Bevis = Marks, London EC3A 7BA, United Kingdom. The companies=E2=80=99 VAT No. is 1= 35539016. Maven Asia (Hong Kong) Ltd (No. 2444041) is registered in Hong Ko= ng and its registered address is 20/F, 198 Wellington St, Hong Kong. =C2=A0= Only Maven Derivatives Ltd and MVN Asset Management Limited are authorised = and regulated by the Financial Conduct Authority (Maven Derivatives Ltd FRN= : 607267, MVN Asset Management Limited FRN: 714429)

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