220 4872 article Path: news.gmane.org!not-for-mail From: carrierandoperator@yahoo.co.uk Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Proposal: std::sequence Date: Tue, 4 Jun 2013 17:52:16 -0700 (PDT) Lines: 157 Approved: news@gmane.org Message-ID: References: <4551abbc-43aa-4520-a91a-f8eb25a90588@isocpp.org> <2c8e6079-9c87-425a-93e2-39251df57cd8@isocpp.org> <9f1cace3-0503-4a3c-a8ce-d7546564b3ef@isocpp.org> <1c991e6e-6bc3-4822-9ffd-7f2508e63974@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_929_15563790.1370393536677" X-Trace: ger.gmane.org 1370393539 4597 80.91.229.3 (5 Jun 2013 00:52:19 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 5 Jun 2013 00:52:19 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDQ2R4E5RIKBBQMXXKGQKGQETFL5BIQ@isocpp.org Wed Jun 05 02:52:20 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-gh0-f198.google.com ([209.85.160.198]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Uk1xb-0008MT-5Z for gclcip-std-proposals@m.gmane.org; Wed, 05 Jun 2013 02:52:19 +0200 Original-Received: by mail-gh0-f198.google.com with SMTP id r13sf398877ghr.9 for ; Tue, 04 Jun 2013 17:52:18 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=x-beenthere: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=v6njFmMjwbt5WNp5GTL9Loe0nlVjbD4WDUfESDbB+HE=; b=UY515LTkb5Cd6uU9Zi1DVSu6hAOA3FAn5K2FacT5+5N3jEpi5dq846MjaktbQBd4E0 xCnZyqK6zefHbIf263w+xEUvkQG/oXnIC3cAl336UqtJuga+fQZIENiiexoBmiba6wI2 yGnQHAFG3Al6YmrweH77dAS7yAiMCZGwu65fNgBfd9Xb1RoeuDUSBU3mOQZ79cRJCByQ gfQmIS+lp8JZS/bj6e9Xq7457WqTIIua8/zpW8FA9aOU4OZKVs8GNKhG6XXeaJpy2bnH EiCPTI9q8mbhAybjkB3s67E9xrXLqP6BNFLOmyT4gen7dJljuPPVLaFtAIjJ+mOeIq2D zPtw== X-Received: by 10.224.205.138 with SMTP id fq10mr17684628qab.1.1370393538222; Tue, 04 Jun 2013 17:52:18 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.48.201 with SMTP id o9ls573631qen.30.gmail; Tue, 04 Jun 2013 17:52:17 -0700 (PDT) X-Received: by 10.49.2.228 with SMTP id 4mr2251748qex.3.1370393537011; Tue, 04 Jun 2013 17:52:17 -0700 (PDT) In-Reply-To: X-Original-Sender: carrierandoperator@yahoo.co.uk 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:4872 Archived-At: ------=_Part_929_15563790.1370393536677 Content-Type: text/plain; charset=ISO-8859-1 On Tuesday, June 4, 2013 6:54:45 PM UTC-4, Jeffrey Yasskin wrote: > > > > Yeah, you might see a performance difference for non-const > array_ref<>s where the compiler can't assume they don't change. If > users see that, they can create const array_ref<>s instead. Is there a > difference between const array_ref<>s and sequence<>s? > Mentioning an update past the initial proposal; there are two forms: template<>class sequence {const T* const element; const size_t size;}; // for immutable elements template<>class mutable_sequence {T* const element; const size_t size;}; // for mutable elements Thus: const array_ref sequence sequence& const sequence const sequence& const mutable_sequence const mutable_sequence& All specify objects which have invariant size and pointer. In all cases, mutable elements may not be provided by the class although they may be externally modified. Naturally, there will also be cases where the optimizer can prove a value of type array_ref does not alter its size or pointer. (excuse the edit noise) -- --- 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 email 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/?hl=en. ------=_Part_929_15563790.1370393536677 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On Tuesday, June 4, 2013 6:54:45 PM UTC-4, Jeffrey Yasskin wrote:<snip>

Yeah, you might see a performance difference for non-const
array_ref<>s where the compiler can't assume they don't change. I= f
users see that, they can create const array_ref<>s instead. Is th= ere a
difference between const array_ref<>s and sequence<>s?

Mentioning an update past the initial = proposal; there are two forms:

template<>= class sequ= ence {const T* const element; const size_t size;}; // for immuta= ble elements
temp= late<&g= t;class mutable_sequ= ence {T* const element; const size_t size;}; = // for mut= able elements


Thus:
const array_ref<int>
sequence<int>
sequence<int>&
const sequence<int>
const s= equence<= ;int>&a= mp;
const<= span style=3D"color: #000;" class=3D"styled-by-prettify"> mutable_sequence<= /span><int>=
const mutable_sequence<int>&<= span style=3D"color: #000;" class=3D"styled-by-prettify">
<= /code>


All specify objects which have invarian= t size and pointer. In all cases, mutable elements may not be provided by t= he class although they may be externally modified.

Naturally, there will also be cases where the optimizer can prove a value = of type array_ref<int> does not alter its size or pointer.
=
 (excuse the edit noise)

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