220 19214 <58625b71-98be-4acb-9815-af1ec2113cc6@isocpp.org> article Path: news.gmane.org!not-for-mail From: "T. C." Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Overloading std::begin and std::end for std::pair Date: Thu, 23 Jul 2015 12:29:23 -0700 (PDT) Lines: 286 Approved: news@gmane.org Message-ID: <58625b71-98be-4acb-9815-af1ec2113cc6@isocpp.org> References: <012fd35d-96fd-4775-835e-2105176c4f97@isocpp.org> <70492682-c1ac-4d67-9c00-fe8d841aae63@isocpp.org> <424cd221-d1c7-4baf-b074-b7f44ee5c82e@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_1057_1728071093.1437679763642" X-Trace: ger.gmane.org 1437679775 23960 80.91.229.3 (23 Jul 2015 19:29:35 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 23 Jul 2015 19:29:35 +0000 (UTC) Cc: vlad.moscow@mail.ru To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCQ43G7NQIIRBFEBYWWQKGQEDV63GCQ@isocpp.org Thu Jul 23 21:29:34 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-oi0-f72.google.com ([209.85.218.72]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ZIMBP-0006K0-B1 for gclcip-std-proposals@m.gmane.org; Thu, 23 Jul 2015 21:29:31 +0200 Original-Received: by oiho132 with SMTP id o132sf2007619oih.1 for ; Thu, 23 Jul 2015 12:29:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=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=azJwWmkPd28QGi4LxVkuQV0vDAcXLa4tNSVBwj07tqI=; b=TFDC4m2vcd0+BuiDe+yAjgkbTceIkzygOKsSBVnDdx8t72VyLZbeCfM7nxzaQH6gJp xStDQTmuehuPUuG89Wq5YBcg20S3Qo6xKR+4/66PFEgH5OPZZc2T1xIznFH5FedLc9lD bqUsyAokpiZx9ubg7t2W1oLK6sP7iN0NAMn7OuSMVkJL1AStH8+x20S+qsLn4WhrRgsd K7XWeRbnHjLIDX4ctwx3VvgNnY4fY3zeYxgtAYmqbx+fNy0L0yVZ7G7XR/zl1N8Gq+wU qiLqyBDJwegG8p+KrJI5txIzq8xAdKeUdpnLMNzafL1MN4XfrUVzEgWi42ZLcAMWQk12 RTag== 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=azJwWmkPd28QGi4LxVkuQV0vDAcXLa4tNSVBwj07tqI=; b=E70JuM0FHUwgGKmUNkNHNK4cE9TYJ/yxkJBlcFiRc9Td0I1WlMtAXbZsA00uwhEPi3 5oI0EWyuROvczl50vZ+N69WxaE0u9Kp0Q3rrDa4pk8jGsRFizavouGW2knm+ZZPn9XyY ZBlK+8+kE+lAuT+lwMp83m+lJOasWuwnaD4r1YF4XtW9weXxAVIInf/2a+RNvxCaeZQV G6Kj4ImlHQyEcfKejfhjI+PFA4x6gYbTg6u4DJdA6+StYdXin7N+0l3IUrZC1dtHAG03 3SX7HOzrEMn/vfuxmKiCE5tRkQgqoxtx2fbC3LQJq3M4ySNPaZEIacjTmR0tnH5NGM0E sXJw== X-Gm-Message-State: ALoCoQm+cjcOcavLaCJvE+2/myFNYgqw0N9I5RyEjZD9b19occhS/sjbDYdHeEvQHw7ai8E0hTV1 X-Received: by 10.182.70.4 with SMTP id i4mr9683148obu.15.1437679765479; Thu, 23 Jul 2015 12:29:25 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.140.104.51 with SMTP id z48ls1142243qge.23.gmail; Thu, 23 Jul 2015 12:29:24 -0700 (PDT) X-Received: by 10.140.20.21 with SMTP id 21mr222240qgi.9.1437679764398; Thu, 23 Jul 2015 12:29:24 -0700 (PDT) In-Reply-To: <424cd221-d1c7-4baf-b074-b7f44ee5c82e@isocpp.org> X-Original-Sender: rs2740@gmail.com 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:19214 Archived-At: ------=_Part_1057_1728071093.1437679763642 Content-Type: multipart/alternative; boundary="----=_Part_1058_888928744.1437679763643" ------=_Part_1058_888928744.1437679763643 Content-Type: text/plain; charset=UTF-8 They existed in an earlier C++0x draft, and were removed by that LWG issue before C++11 was published. Not all pairs of iterators are ranges. Not even all pairs of iterators returned by functions in the standard library are ranges, as your own code with minmax_element demonstrates. Besides, a range class that wraps a pair of iterators is trivial to implement. On Thursday, July 23, 2015 at 3:15:05 PM UTC-4, Vlad from Moscow wrote: > > There is nothing said about introducing functions std::begin and std:;end > for std::pair. > > On Thursday, July 23, 2015 at 9:52:23 PM UTC+3, T. C. wrote: >> >> http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#1381 >> >> >> On Thursday, July 23, 2015 at 2:30:02 PM UTC-4, Vlad from Moscow wrote: >>> >>> And one more example :) >>> >>> #include >>> #include >>> #include >>> #include >>> #include >>> >>> namespace std >>> { >>> template >>> Iterator begin( const std::pair &p ) >>> { >>> return p.first; >>> } >>> template >>> Iterator end( const std::pair &p ) >>> { >>> return p.second; >>> } >>> } >>> int main() >>> { >>> std::vector v = { 3, 4, 0, 5, 1, 6, 9, 7, 8 }; >>> >>> for ( auto x : v ) std::cout << x << ' '; >>> std::cout << std::endl; >>> auto p = std::minmax_element( v.begin(), v.end() ); >>> >>> if ( std::distance( v.begin(), p.second ) < std::distance( >>> v.begin(), p.first ) ) >>> { >>> std::swap( p.first, p.second ); >>> } >>> for ( auto x : p ) std::cout << x << ' '; >>> std::cout << std::endl; >>> } >>> >>> The program output is >>> >>> 3 4 0 5 1 6 9 7 8 >>> 0 5 1 6 >>> >>> On Thursday, July 23, 2015 at 8:57:38 PM UTC+3, Vlad from Moscow wrote: >>> >>>> Another example >>>> >>>> #include >>>> #include >>>> #include >>>> >>>> namespace std >>>> { >>>> >>>> template >>>> Iterator begin( const std::pair &p ) >>>> { >>>> return p.first; >>>> } >>>> >>>> template >>>> Iterator end( const std::pair &p ) >>>> { >>>> return p.second; >>>> } >>>> >>>> } >>>> >>>> int main() >>>> { >>>> std::vector v = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 }; >>>> >>>> for ( auto x : std::make_pair( v.begin(), v.end() ) ) std::cout << >>>> x << ' '; >>>> std::cout << std::endl; >>>> >>>> for ( auto x : std::make_pair( v.rbegin(), v.rend() ) ) std::cout >>>> << x << ' '; >>>> std::cout << std::endl; >>>> } >>>> >>>> The program output is >>>> >>>> 0 1 2 3 4 5 6 7 8 9 >>>> 9 8 7 6 5 4 3 2 1 0 >>>> >>>> Enjoy!:) >>>> >>>> On Thursday, July 23, 2015 at 8:36:46 PM UTC+3, Vlad from Moscow wrote: >>>> >>>>> I'd like to suggest very simple and at the same time very useful >>>>> overloaded functions std::begin and std::end for standard class std::pair. >>>>> >>>>> Here is a demonstrative program of the idea >>>>> >>>>> #include >>>>> #include >>>>> >>>>> namespace std >>>>> { >>>>> template >>>>> Iterator begin( const std::pair &p ) >>>>> { >>>>> return p.first; >>>>> } >>>>> template >>>>> Iterator end( const std::pair &p ) >>>>> { >>>>> return p.second; >>>>> } >>>>> } >>>>> >>>>> int main() >>>>> { >>>>> int a[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 }; >>>>> >>>>> for ( auto x : std::make_pair( a + 3, a + 7 ) ) std::cout << x << >>>>> ' '; >>>>> std::cout << std::endl; >>>>> >>>>> int b[][3] = { { 1, 2, 3 }, { 4, 5, 6 } }; >>>>> >>>>> for ( auto x : std::make_pair( b[0] + 1, b[1] + 2 ) ) std::cout << >>>>> x << ' '; >>>>> std::cout << std::endl; >>>>> } >>>>> >>>>> The program output is >>>>> >>>>> 3 4 5 6 >>>>> 2 3 4 5 >>>>> >>>> -- --- 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/. ------=_Part_1058_888928744.1437679763643 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
They existed in an earlier C++0x draft, and were removed b= y that LWG issue before C++11 was published.

Not all pai= rs of iterators are ranges. Not even all pairs of iterators returned by fun= ctions in the standard library are ranges,
as your own code with = minmax_element demonstrates.

Besides, a range clas= s that wraps a pair of iterators is trivial to implement.

On = Thursday, July 23, 2015 at 3:15:05 PM UTC-4, Vlad from Moscow wrote:
There is nothing sai= d about introducing functions std::begin and std:;end for std::pair.
On Thursday, July 23, 2015 at 9:52:23 PM UTC+3, T. C. wrote:

On Thursday, July 23, 2015 at 2:30:02 PM U= TC-4, Vlad from Moscow wrote:
And one= more example :)

#include <iostream>
#inc= lude <utility>
#include <vector>
#include <algorithm&g= t;
#include <iterator>

namespace std
{= =C2=A0=C2=A0=C2=A0
template <class Iterator>
Iterator begin( c= onst std::pair<Iterator, Iterator> &p )
{
=C2=A0=C2=A0=C2= =A0 return p.first;
}
template <class Iterator>
Itera= tor end( const std::pair<Iterator, Iterator> &p )
{
=C2=A0= =C2=A0=C2=A0 return p.second;
}
}
int main()
{
=C2=A0= =C2=A0=C2=A0 std::vector<int> v =3D { 3, 4, 0, 5, 1, 6, 9, 7, 8 };=C2=A0=C2=A0=C2=A0
=C2=A0=C2=A0=C2=A0 for ( auto x : v ) std::cout <= ;< x << ' ';
=C2=A0=C2=A0=C2=A0 std::cout << std:= :endl;
=C2=A0=C2=A0=C2=A0 auto p =3D std::minmax_element( v.begin= (), v.end() );
=C2=A0=C2=A0=C2=A0
=C2=A0=C2=A0=C2=A0 if ( std::dista= nce( v.begin(), p.second ) < std::distance( v.begin(), p.first ) )
= =C2=A0=C2=A0=C2=A0 {
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 std::swa= p( p.first, p.second );
=C2=A0=C2=A0=C2=A0 }=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0
=C2=A0=C2=A0=C2=A0 for ( auto x : p ) std::cout = << x << ' ';
=C2=A0=C2=A0=C2=A0 std::cout << s= td::endl;
}=C2=A0=C2=A0=C2=A0

The program = output is

3 4 0 5 1 6 9 7 8
0 5 1 6
=
On Thursday, July 23, 2015 at 8:57:38 PM UTC+3, Vlad from Moscow wrote:=
Another example

=
#include <iostream>
#include <utility>
#includ= e <vector>

namespace std
{=C2=A0=C2=A0=C2= =A0

template <class Iterator>
Iterat= or begin( const std::pair<Iterator, Iterator> &p )
{
=C2=A0= =C2=A0=C2=A0 return p.first;
}

template <cla= ss Iterator>
Iterator end( const std::pair<Iterator, Iterator> = &p )
{
=C2=A0=C2=A0=C2=A0 return p.second;
}
}

int main()
{
=C2=A0=C2=A0=C2= =A0 std::vector<int> v =3D { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
=C2= =A0=C2=A0=C2=A0
=C2=A0=C2=A0=C2=A0 for ( auto x : std::make_pair( v.beg= in(), v.end() ) ) std::cout << x << ' ';
=C2=A0=C2= =A0=C2=A0 std::cout << std::endl;
=C2=A0=C2=A0=C2=A0
=C2=A0=C2= =A0=C2=A0 for ( auto x : std::make_pair( v.rbegin(), v.rend() ) ) std::cout= << x << ' ';
=C2=A0=C2=A0=C2=A0 std::cout << = std::endl;
}=C2=A0=C2=A0=C2=A0

The = program output is

0 1 2 3 4 5 6 7 8 9
9 8 7 6 = 5 4 3 2 1 0

Enjoy!:)

On Thursday, July 23, = 2015 at 8:36:46 PM UTC+3, Vlad from Moscow wrote:
I'd like to =C2=A0suggest very simple and=C2=A0at th= e same time very useful=C2=A0 overloaded functions std::begin and std::end = for standard class std::pair.

Here is a demonstrat= ive program of the idea

#include <iostream><= /div>
#include <utility>

namespace std{=C2=A0=C2=A0=C2=A0
template <class Iterator>
Iterator begin= ( const std::pair<Iterator, Iterator> &p )
{
=C2=A0=C2=A0= =C2=A0 return p.first;
}
template <class Iterator>
It= erator end( const std::pair<Iterator, Iterator> &p )
{
=C2= =A0=C2=A0=C2=A0 return p.second;
}
}

int mai= n()
{
=C2=A0=C2=A0=C2=A0 int a[] =3D { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 }= ;
=C2=A0=C2=A0=C2=A0
=C2=A0=C2=A0=C2=A0 for ( auto x : std::make_pai= r( a + 3, a + 7 ) ) std::cout << x << ' ';
=C2=A0=C2= =A0=C2=A0 std::cout << std::endl;
=C2=A0=C2=A0=C2=A0=C2=A0<= br>=C2=A0=C2=A0=C2=A0 int b[][3] =3D { { 1, 2, 3 }, { 4, 5, 6 } };
=C2=A0=C2=A0=C2=A0=C2=A0
=C2=A0=C2=A0=C2=A0 for ( auto x : std::make_p= air( b[0] + 1, b[1] + 2 ) ) std::cout << x << ' ';
= =C2=A0=C2=A0=C2=A0 std::cout << std::endl;
}

<= div>The program output is

3 4 5 6
2 3 4 5=C2= =A0=C2=A0=C2=A0

--

---
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>.
------=_Part_1058_888928744.1437679763643-- ------=_Part_1057_1728071093.1437679763642-- .