220 6213 article Path: news.gmane.org!not-for-mail From: =?ISO-8859-1?Q?Daniel_Kr=FCgler?= Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Specialization of std::stack for std::forward_list Date: Sat, 7 Sep 2013 12:32:37 +0200 Lines: 130 Approved: news@gmane.org Message-ID: References: <419bda08-54a2-43e7-8dd7-ade5bf47cf88@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=001a11c2b36a8306b404e5c8acdb X-Trace: ger.gmane.org 1378549956 11298 80.91.229.3 (7 Sep 2013 10:32:36 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sat, 7 Sep 2013 10:32:36 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCT7RVFA4QORBRUBVSIQKGQES3CGHWQ@isocpp.org Sat Sep 07 12:32:40 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-bk0-f71.google.com ([209.85.214.71]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1VIFol-0005LZ-Dk for gclcip-std-proposals@m.gmane.org; Sat, 07 Sep 2013 12:32:39 +0200 Original-Received: by mail-bk0-f71.google.com with SMTP id e11sf3461601bkh.2 for ; Sat, 07 Sep 2013 03:32:38 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :x-original-sender:x-original-authentication-results:reply-to :precedence:mailing-list:list-id:list-post:list-help:list-archive :list-subscribe:list-unsubscribe:content-type; bh=LZPbiqCsep5y5snGi9tkl3CDwhVbWpEQIJmdfVu4IYg=; b=QVSCseZyJxBj6E00CYk2PdFQRp6UOlf0RoTEvfXj7ZQcoxP/vEdaCPGUvM6RcvqrGh DMl+YrJJZGjIKkn6V3X4f7x5F8xrbmh6udDHVVAsZBcUGOog3E9FeffX5oxRwqnMYcee OQk40m1xzCkl8HpHrAihd9bJhzNj535doI7OakACY10+HQ4iJbU/9MkKosi/J1MBWwf1 ubH9hP01D+316JIe7sQBlcsxEmwpyXqG2KQNrmCw9FmQq+M9ELWFkpyC5gvy/yCA7+kx o2iSw/Pdbahs/ptKDBcuY33Ix67EMwQyw3JshJ6n81MXwX3BIEXeZH4kTr6jTZ/hP6WM BkEA== X-Received: by 10.180.80.227 with SMTP id u3mr693573wix.5.1378549958809; Sat, 07 Sep 2013 03:32:38 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.180.88.106 with SMTP id bf10ls356653wib.17.gmail; Sat, 07 Sep 2013 03:32:37 -0700 (PDT) X-Received: by 10.180.13.13 with SMTP id d13mr1765058wic.34.1378549957678; Sat, 07 Sep 2013 03:32:37 -0700 (PDT) Original-Received: from mail-wg0-x22c.google.com (mail-wg0-x22c.google.com [2a00:1450:400c:c00::22c]) by mx.google.com with ESMTPS id q5si947222wij.24.1969.12.31.16.00.00 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sat, 07 Sep 2013 03:32:37 -0700 (PDT) Received-SPF: pass (google.com: domain of daniel.kruegler@gmail.com designates 2a00:1450:400c:c00::22c as permitted sender) client-ip=2a00:1450:400c:c00::22c; Original-Received: by mail-wg0-f44.google.com with SMTP id b12so2640789wgh.11 for ; Sat, 07 Sep 2013 03:32:37 -0700 (PDT) X-Received: by 10.180.10.136 with SMTP id i8mr1743063wib.46.1378549957328; Sat, 07 Sep 2013 03:32:37 -0700 (PDT) Original-Received: by 10.216.153.8 with HTTP; Sat, 7 Sep 2013 03:32:37 -0700 (PDT) In-Reply-To: X-Original-Sender: daniel.kruegler@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of daniel.kruegler@gmail.com designates 2a00:1450:400c:c00::22c as permitted sender) smtp.mail=daniel.kruegler@gmail.com; dkim=pass header.i=@gmail.com; dmarc=pass (p=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:6213 Archived-At: --001a11c2b36a8306b404e5c8acdb Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable 2013/9/7 Tony V E > > On Fri, Sep 6, 2013 at 5:01 PM, Daniel Kr=FCgler wrote: > >> > >> > Bit of a tangent here - I'm surprised forward_list doesn't have a >> size(), >> > since, as you say, it wouldn't be hard to implement. >> >> See >> >> http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2543.htm >> >> for the design rationale, especially regarding the omission of size(). >> >> > Thanks for the link. Note that it says: > > "Note that similar considerations apply to std::list::size()." > > Which, (IIUC) at the time, didn't require O(1) size(), but now does. > Wonder if forward_list is worth revisiting. > For std::list there was decision to make in regard to trade-of between size() and splice(), see http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2009/n2923.pdf But list was a container that should *fully* satisfy the container requirements, therefore the size() member existed from the C++98. Here we had not choice to remove size() from list. For forward_list the design idea was intentionally not to satisfy the container requirements, but instead to provide a type that does not take more space or time overhead relative to a hand-written C-style singly linked list, see the note added to [forwardlist.overview] p1, especially "Features that would conflict with that goal have been omitted." and the text in above quoted paper. It is certainly possible to add a size() member with O(1) guarantee but that would conflict with the design idea. Of-course reconsidering previous ideas is always possible, but would probably require a paper that provides some convincing arguments for such a change. - Daniel --=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/. --001a11c2b36a8306b404e5c8acdb Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable

= 2013/9/7 Tony V E <tvaneerd@gmail.com>

On Fri, Sep 6, 2013 at 5:01 PM, Daniel Kr=FCgler <daniel.kruegler@gmail.com> wrote:
>
> Bit of a tangent here - I'm surprised forward_list doesn't hav= e a size(),
> since, as you say, it wouldn't be hard to implement.

See

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/200= 8/n2543.htm

for the design rationale, especially regarding the omission of size().


Thanks fo= r the link.=A0 Note that it says:

"Note that similar considerat= ions apply to std::list::size()."
=
Which, (IIUC) at the time, didn't = require O(1) size(), but now does.=A0 Wonder if forward_list is worth revis= iting.

For std::list there was decis= ion to make in regard to trade-of between size() and splice(), see

<= a href=3D"http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2009/n2923.pdf= ">http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2009/n2923.pdf

But list was a container that should *= fully* satisfy the container requirements, therefore the size() member exis= ted from the C++98. Here we had not choice to remove size() from list.

For forward_list the design idea was intentionally not to satisfy the c= ontainer requirements, but instead to provide a type that does not take mor= e space or time overhead relative to a hand-written C-style singly linked l= ist, see the note added to [forwardlist.overview] p1, especially "Feat= ures that would conflict with that goal have been omitted." and the te= xt in above quoted paper. It is certainly possible to add a size() member w= ith O(1) guarantee but that would conflict with the design idea. Of-course = reconsidering previous ideas is always possible, but would probably require= a paper that provides some convincing arguments for such a change.

- Daniel

--
 
---
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-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-proposals/<= /a>.
--001a11c2b36a8306b404e5c8acdb-- .