220 13702 article Path: news.gmane.org!not-for-mail From: Tony V E Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Generic std::size, a la std::begin Date: Mon, 6 Oct 2014 10:40:27 -0400 Lines: 176 Approved: news@gmane.org Message-ID: References: <8808df5e-62c4-459d-acd9-00e63adb9476@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=001a11c372da504caf0504c2108d X-Trace: ger.gmane.org 1412606439 25709 80.91.229.3 (6 Oct 2014 14:40:39 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 6 Oct 2014 14:40:39 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCUZ5QWKNQINZU6KUECRUBGI6NI7I@isocpp.org Mon Oct 06 16:40:34 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ee0-f72.google.com ([74.125.83.72]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Xb9Sg-0005aI-1C for gclcip-std-proposals@m.gmane.org; Mon, 06 Oct 2014 16:40:30 +0200 Original-Received: by mail-ee0-f72.google.com with SMTP id e51sf2969109eek.7 for ; Mon, 06 Oct 2014 07:40:29 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state: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=xSpzOLNGhn2sRfNgjiC/upkOUFRAOJuTABbdMPfF/KA=; b=jWvmhfUUq43zt8Ey3TLMiVJfcPfVf+Frcl1iRg5uPfQoSuCcvuukrv4Kam/Yo5fs2p RNncclHD5i+LqwrQEpDt8mEAllSS1EqzqOyoXKzhLiLOK2sl1dSqAbmMbQbZEnL5ofZo +vQ/P8hnoEXSctEIf5F2kYRyaelU3GLv3jIZyb3cxNBmrU9NIDHicLvWt7VBBGhT4L0D DQs1+GoLqBfe6BuDiUZQ0gCF12GyHlk+Beof+OGsXDiBff9QtpGQ/DSdMuCrPIPPhYSF bIRGw9VjUs+2tREQvoz4Q3DvpoTXU65q2Cm0n23189PK4XNHr3Nv7z034tkLpufANG9A iFnA== X-Gm-Message-State: ALoCoQlS3cF0MSTYypL4N+3n/x1OPdzMcBnuYYpqmbrmPwDot9lThstujD9+SJo2HFMJ2cmdFvkI X-Received: by 10.180.106.197 with SMTP id gw5mr2592651wib.1.1412606429672; Mon, 06 Oct 2014 07:40:29 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.152.23.227 with SMTP id p3ls602805laf.39.gmail; Mon, 06 Oct 2014 07:40:28 -0700 (PDT) X-Received: by 10.112.126.194 with SMTP id na2mr24087828lbb.70.1412606428136; Mon, 06 Oct 2014 07:40:28 -0700 (PDT) Original-Received: from mail-la0-x234.google.com (mail-la0-x234.google.com [2a00:1450:4010:c03::234]) by mx.google.com with ESMTPS id b2si24367668lah.6.2014.10.06.07.40.28 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 06 Oct 2014 07:40:28 -0700 (PDT) Received-SPF: pass (google.com: domain of tvaneerd@gmail.com designates 2a00:1450:4010:c03::234 as permitted sender) client-ip=2a00:1450:4010:c03::234; Original-Received: by mail-la0-f52.google.com with SMTP id hz20so4452922lab.39 for ; Mon, 06 Oct 2014 07:40:27 -0700 (PDT) X-Received: by 10.112.201.72 with SMTP id jy8mr24510826lbc.78.1412606427416; Mon, 06 Oct 2014 07:40:27 -0700 (PDT) Original-Received: by 10.112.75.199 with HTTP; Mon, 6 Oct 2014 07:40:27 -0700 (PDT) In-Reply-To: <8808df5e-62c4-459d-acd9-00e63adb9476@isocpp.org> X-Original-Sender: tvaneerd@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of tvaneerd@gmail.com designates 2a00:1450:4010:c03::234 as permitted sender) smtp.mail=tvaneerd@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:13702 Archived-At: --001a11c372da504caf0504c2108d Content-Type: text/plain; charset=UTF-8 On Wed, Oct 1, 2014 at 4:00 AM, Jeaye Wilkerson wrote: > Folks, > > The stdlib could use a few new function templates to aid in creating > generic interfaces. With C++11, we were given std::begin to account for the > fact that C-style arrays are valid containers. I propose we add a very > similar set of functions of accessing the size of containers, including > C-style arrays. The interface is as follows: > > template > > auto size(T &c); > template > auto size(T const &c); > template > std::size_t constexpr size(T (&arr)[N]); > > > A working implementation and some example code is included here: > http://coliru.stacked-crooked.com/a/a321818e19f0efae > > The two main benefits of this addition are as follows: > > 1. Support for C-style arrays in generic implementations; this also > makes the std::xxx_n series more compatible with C-style arrays > 2. Allowance of user-provided fully specialized versions of std::size > for custom types > > An example of 2 being: > http://coliru.stacked-crooked.com/a/12c71f9970e37463 > > Regards, > Jeaye > > -- > > > I would like something like this, and have written it myself a number of times. It would be nice to have a consistent name for it. One concern I have, however, is how we do library extension points, in general. ie it is hard to call swap(x,y) correctly: { using std::swap; swap(x, y); } Will users need to do the same for std::size? In general, I'd prefer the customization/extension point be separate from the caller's API. ie customize std_size(), but call std::size(). To me (at least) this is similar to Herb's "Non-Virtual Interface" idiom ( http://www.gotw.ca/publications/mill18.htm). IN this case, there is no virtual functions, but the separation of caller-interface vs customizer-interface is the same. Tony -- --- 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/. --001a11c372da504caf0504c2108d Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable


On Wed, Oct 1, 2014 at 4:00 AM, Jeaye Wilkerson <<= a href=3D"mailto:contact@jeaye.com" target=3D"_blank">contact@jeaye.com= > wrote:
Folks,

The stdlib could use a few new function templat= es to aid in creating generic interfaces. With C++11, we were given std::be= gin to account for the fact that C-style arrays are valid containers. I pro= pose we add a very similar set of functions of accessing the size of contai= ners, including C-style arrays. The interface is as follows:

template <= /span><typename T>
auto size<=
span style=3D"color:rgb(102,102,0)">(T &c);
template <typename T>
auto s=
ize(T const &am=
p;c);
template <typename T,<=
/span> std::size_t N>=

std::size_t con=
stexpr size(T (&arr)[N]);

A working implementation and some example code is= included here: http://coliru.stacked-crooked.com/a/a321818e19f0efa= e

The two main benefits of this addition are as follows:
    =
  1. Support for C-style arrays in generic implementations; this also makes = the std::xxx_n series more compatible with C-style arrays
  2. Allowance= of user-provided fully specialized versions of std::size for custom types<= /li>

An example of 2 being: http://coliru.stacked-crooked.co= m/a/12c71f9970e37463

Regards,
Jeaye

--




I would like som= ething like this, and have written it myself a number of times.=C2=A0 It wo= uld be nice to have a consistent name for it.

One concern= I have, however, is how we do library extension points, in general.=C2=A0 = ie it is hard to call swap(x,y) correctly:

{
=C2=A0=C2= =A0 using std::swap;
=C2=A0=C2=A0 swap(x, y);
}

Will users need to do the same for std::size?

In = general, I'd prefer the customization/extension point be separate from = the caller's API.=C2=A0 ie customize std_size(), but call std::size().<= br>
To me (at least) this is similar to Herb's "Non-= Virtual Interface" idiom (http://www.gotw.ca/publications/mill18.htm).=C2=A0 IN this c= ase, there is no virtual functions, but the separation of caller-interface = vs customizer-interface is the same.

Tony


--

---
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-proposa= ls+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>.
--001a11c372da504caf0504c2108d-- .