220 22022 <6b98496b-ea50-4155-8560-4fd0d445a5c5@isocpp.org> article Path: news.gmane.org!not-for-mail From: Vlad from Moscow Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: New compound assignment operators.:) Date: Tue, 27 Oct 2015 13:27:23 -0700 (PDT) Lines: 140 Approved: news@gmane.org Message-ID: <6b98496b-ea50-4155-8560-4fd0d445a5c5@isocpp.org> References: Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_6950_928031894.1445977643740" X-Trace: ger.gmane.org 1445977647 31152 80.91.229.3 (27 Oct 2015 20:27:27 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Tue, 27 Oct 2015 20:27:27 +0000 (UTC) Cc: mwoehlke.floss@gmail.com To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCXLLRHD7IDRBLF4X6YQKGQECRZF67A@isocpp.org Tue Oct 27 21:27:27 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yk0-f198.google.com ([209.85.160.198]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ZrAq6-0002Dl-93 for gclcip-std-proposals@m.gmane.org; Tue, 27 Oct 2015 21:27:26 +0100 Original-Received: by ykdy125 with SMTP id y125sf380484392ykd.3 for ; Tue, 27 Oct 2015 13:27:25 -0700 (PDT) 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:cc:message-id:in-reply-to :references:subject:mime-version:content-type: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=+ifshlqWFIGDSw3TlRJgu0JxAGDxuXTiqYLnYj6cCbA=; b=mHzpEsqRdhgyMsI3aAU6tr0z+8L7cB7EunDHOQuvxzew2ac9HcNRn6bFyk0sSVfaCK ml9FbJbK3HuuJ3G/jMKK6Z74/BqHnw9spTilE2tuZ2wM6Yyhp0f4h3bj6eSHDYA9t20P rXYm1D2deHP0cksIGP1vDNCCtktwLIu5KBLznpFsSfvJvBPzlZgGFCC7iu29lS0nlblx YSJYfR+dtJ28TCz+rSuwcDZGp82PH+BFsoCVqnQS/oC0GPNIMi6g9GblJNypnuWhoq12 l10BpdUsnygKG05rHhHKN3LKvaW93rw9eMzeO8wBTlENZYV59G1brWrVQ5sqi1NHddtH sAww== X-Gm-Message-State: ALoCoQmFxi2K6KInHbVoOPDC7NPsRgUV/KBS9UVuntW6AOu2rL5RgWlkZ09mju4THDo7P00vW20B X-Received: by 10.140.176.140 with SMTP id w134mr8355167qhw.6.1445977645468; Tue, 27 Oct 2015 13:27:25 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.50.78.202 with SMTP id d10ls1330727igx.41.canary; Tue, 27 Oct 2015 13:27:24 -0700 (PDT) X-Received: by 10.50.20.7 with SMTP id j7mr13571ige.1.1445977644428; Tue, 27 Oct 2015 13:27:24 -0700 (PDT) In-Reply-To: X-Original-Sender: vlad.moscow@mail.ru Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Spam-Checked-In-Group: std-proposals@isocpp.org 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:22022 Archived-At: ------=_Part_6950_928031894.1445977643740 Content-Type: multipart/alternative; boundary="----=_Part_6951_1719810581.1445977643740" ------=_Part_6951_1719810581.1445977643740 Content-Type: text/plain; charset=UTF-8 On Tuesday, October 27, 2015 at 11:13:12 PM UTC+3, Matthew Woehlke wrote: > > On 2015-10-27 16:00, Vlad from Moscow wrote: > > So the idea is to introduce compound operators like :) > > > > =+, =-,=*, =/, =% > > At least the first two can't happen: > > // Currently valid code > x =+ 2; > y =- 4; > // x == 2, y == -4 > > Even adding ()'s won't help. > > I'm not necessarily saying that the idea itself is bad, but the proposed > syntax is not feasible. > > -- > Matthew > > It is enough often when I am writing a predicate for an algorithm I need to return the result of a comparison or other logical operator. But before to return the result I need to do some action with one of arguments or a captured cariable that takes part in the logical expression. So I have to introduce a boolean variable that to keep the result then do the action and only after that return the result. The idea came to my head when I was answering the following question at SO http://stackoverflow.com/questions/33375769/a-zero-indexed-array-given-an-equilibrium-index-of-this-array/33376721#33376721 Instead of writing three statements in the if statement for ( size_t i = 0; i < sizeof( a ) / sizeof( *a ); i++ ) { right_sum -= a[i]; if ( left_sum == right_sum ) std::cout << i << ' '; left_sum += a[i]; } I could write only one statement :) for ( size_t i = 0; i < sizeof( a ) / sizeof( *a ); i++ ) { if ( ( left_sum =+ a[i] ) == ( right_sum -= a[i] ) ) std::cout << i << ' '; } -- --- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. 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On Tuesday, October 27, 2015 at 11:13:12 PM UTC+3,= Matthew Woehlke wrote:
On 2015-10-27 16:00, Vl= ad from Moscow wrote:
> So the idea is to introduce compound operators like :)
>=20
> =3D+, =3D-,=3D*, =C2=A0=3D/, =3D%=20

At least the first two can't happen:

=C2=A0 // Currently valid code
=C2=A0 x =3D+ 2;
=C2=A0 y =3D- 4;
=C2=A0 // x =3D=3D 2, y =3D=3D -4

Even adding ()'s won't help.

I'm not necessarily saying that the idea itself is bad, but the pro= posed
syntax is not feasible.

--=20
Matthew


It is enough often=C2=A0=C2=A0when I a= m writing a predicate for an algorithm I need to return the result of a com= parison or other logical operator. But before to return the result I need t= o do some action with one of arguments or a captured cariable that takes pa= rt in the logical expression. So I have to introduce a boolean variable tha= t to keep the result then do the action and only after that return the resu= lt.


Instead of writing three statements in the if statement

=C2=A0=C2=A0=C2=A0 for ( size_t= i =3D 0; i < sizeof( a ) / sizeof( *a ); i++ )
=C2=A0=C2=A0=C2=A0 {<= br>=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 right_sum -=3D a[i];
=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if ( left_sum =3D=3D right_sum )=C2= =A0std::cout << i << ' ';
=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0 left_sum +=3D a[i];
=C2=A0=C2=A0=C2=A0 }
=C2=A0
I could write only one statement :)
=C2=A0=C2=A0=C2=A0 for ( size_t i =3D 0; i < sizeof( a ) / s= izeof( *a ); i++ )
=C2=A0=C2=A0=C2=A0 {
=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0 if ( ( left_sum =3D+ a[i]=C2=A0)=C2=A0=3D=3D ( right_sum -= =3D a[i] ) )=C2=A0std::cout << i << ' ';
=C2=A0=C2= =A0=C2=A0 }

--

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