220 2750 article Path: news.gmane.org!not-for-mail From: =?UTF-8?Q?Andrzej_Krzemie=C5=84ski?= Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: A proposal to add swap traits to the standard library Date: Wed, 6 Feb 2013 02:34:34 -0800 (PST) Lines: 116 Approved: news@gmane.org Message-ID: References: <1359827596.1381.2.camel@Nokia-N900> <41C25E3D-C254-43AE-BFEA-ED83B7DAF74E@gmail.com> <510E1906.3030604@wanadoo.fr> <91576F12-5D5E-45A5-AFC1-E5A4D80052C8@gmail.com> <510EC81E.6050803@gmail.com> <510F45EA.1080308@gmail.com> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_401_4838259.1360146874472" X-Trace: ger.gmane.org 1360146879 25385 80.91.229.3 (6 Feb 2013 10:34:39 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 6 Feb 2013 10:34:39 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDT2DGOJ34DBBO7DZCEAKGQEWCBNBYA@isocpp.org Wed Feb 06 11:35:01 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-gg0-f198.google.com ([209.85.161.198]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1U32L8-00067K-NU for gclcip-std-proposals@m.gmane.org; Wed, 06 Feb 2013 11:34:55 +0100 Original-Received: by mail-gg0-f198.google.com with SMTP id a5sf654706ggn.1 for ; Wed, 06 Feb 2013 02:34:35 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=x-received:x-beenthere:x-received: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=0uejWijRwtcK2ArHMO8PSjPMCtji1lpZbNygLwfPdHU=; b=nn0cTBczr/mzqxArgphoTrDTzXATkYsxi53wqU7FaP/CFuyUDgLr0s82baMMeIHFky 7SpuLCcLuTS454r2OH7r97pNn5OQEqYZgYcVno+MImhOS4oc/oLpaKHAXu6bETf3er/j MT8ZZijAmANBR926qwrMIOfiIzLW12KlghckHtoTfUC0jOANlIz0YXWXBfXnKry9sEY/ 7UuCc9OJGn9cGkmgOstYgQFiKhQ2Gc8uaQ8v6ba7r2QkSGt0G6081IBwjalYbYB1/bch fyZqMwNoXRlFTcX6qWDCC7cqitvZA3J6lqDUjn0pe76h1z787rDRjoha77n/xCrYVX+q t6CA== X-Received: by 10.236.126.194 with SMTP id b42mr13147262yhi.23.1360146875349; Wed, 06 Feb 2013 02:34:35 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.37.134 with SMTP id y6ls284296qej.96.gmail; Wed, 06 Feb 2013 02:34:34 -0800 (PST) X-Received: by 10.49.96.196 with SMTP id du4mr2442965qeb.37.1360146874799; Wed, 06 Feb 2013 02:34:34 -0800 (PST) In-Reply-To: <510F45EA.1080308@gmail.com> X-Original-Sender: akrzemi1@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:2750 Archived-At: ------=_Part_401_4838259.1360146874472 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable W dniu poniedzia=C5=82ek, 4 lutego 2013 06:23:54 UTC+1 u=C5=BCytkownik Mika= el=20 Kilpel=C3=A4inen napisa=C5=82: > > 3.2.2013 21:27, Mikael Kilpel=C3=AF=C2=BF=C2=BDinen kirjoitti:=20 > >=20 > > template=20 > > void foo(T&, T&) noexcept(noexcept( std::tuple().swap(=20 > > std::declval&>() )));=20 > >=20 > >=20 > Seems i was already sleeping when i wrote that, as obviously this=20 > imposes some restrictions for T but maybe the concept works as a dirty=20 > workaround.=20 > > So lets summarise most of the thread :=20 > > - Problem exists with free functions and lookup if wanted to use in=20 > noexcept, trailing return=20 > - Having is_swappable traits (as proposed) fixes it for one of the most= =20 > common cases, and i do agree it feels like those type traits are missing.= =20 > - We might be able to fix this for most std free functions by making=20 > them first to perform ADL like pointed out by Yasskin. I wonder how many= =20 > swap relies on calling the std::swap directly though and possibly=20 > recursing then.=20 > > The problem itself it generic, but is it worth "fixing"? Is there much=20 > similar usage with other than std library that would benefit from it?=20 > If the problem is primarily about std::swap, and swap is so very special,= =20 perhaps defining or aliasing it in the global namespace would solve the=20 problem?=20 --=20 ---=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. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposa= ls/?hl=3Den. ------=_Part_401_4838259.1360146874472 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable

W dniu poniedzia=C5=82ek, 4 lutego 2013 06:23:54 UTC+1 u=C5=BCytkow= nik Mikael Kilpel=C3=A4inen napisa=C5=82:
3.2.2013 21:27, Mikael Kilpel=C3=AF=C2=BF=C2=BDinen kirjoitti:
>
> template<typename T>
> void foo(T&, T&) noexcept(noexcept( std::tuple<T>().= swap(=20
> std::declval<std::tuple<T>&>() )));
>
>
Seems i was already sleeping when i wrote that, as obviously this=20
imposes some restrictions for T but maybe the concept works as a dirty= =20
workaround.

So lets summarise most of the thread :

- Problem exists with free functions and lookup if wanted to use in=20
noexcept, trailing return
- Having is_swappable traits (as proposed) fixes it for one of the most= =20
common cases, and i do agree it feels like those type traits are missin= g.
- We might be able to fix this for most std free functions by making=20
them first to perform ADL like pointed out by Yasskin. I wonder how man= y=20
swap relies on calling the std::swap directly though and possibly=20
recursing then.

The problem itself it generic, but is it worth "fixing"? Is there much= =20
similar usage with other than std library that would benefit from it?

If the problem is primarily about std::swap, and = swap is so very special, perhaps defining or aliasing it in the global name= space would solve the problem?

--
 
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