220 19216 article Path: news.gmane.org!not-for-mail From: Vlad from Moscow Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Overloading std::begin and std::end for std::pair Date: Thu, 23 Jul 2015 12:35:12 -0700 (PDT) Lines: 300 Approved: news@gmane.org Message-ID: References: <012fd35d-96fd-4775-835e-2105176c4f97@isocpp.org> <70492682-c1ac-4d67-9c00-fe8d841aae63@isocpp.org> <424cd221-d1c7-4baf-b074-b7f44ee5c82e@isocpp.org> <58625b71-98be-4acb-9815-af1ec2113cc6@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_830_236881370.1437680112775" X-Trace: ger.gmane.org 1437680122 29401 80.91.229.3 (23 Jul 2015 19:35:22 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 23 Jul 2015 19:35:22 +0000 (UTC) Cc: rs2740@gmail.com To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCXLLRHD7IDRB4MDYWWQKGQEAOFE5BQ@isocpp.org Thu Jul 23 21:35:20 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ob0-f200.google.com ([209.85.214.200]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ZIMH2-0000ug-78 for gclcip-std-proposals@m.gmane.org; Thu, 23 Jul 2015 21:35:20 +0200 Original-Received: by obbtu2 with SMTP id tu2sf1951969obb.1 for ; Thu, 23 Jul 2015 12:35:14 -0700 (PDT) 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=MIvIKED8VUGOLTWuOYRtL1B/OxlUpG6vvvW2QfFaxp8=; b=fVWGVdcO7z/IV/SHG2ccxMKB4569SkEr4GUfsu1GxWufQPUJXMHsPjAGYzEFFICtcf iCkRjcKxxU3GMACnZTJGIa0PphTayHLEXGymWdWB1B/NrOnL/pzdvUVsKwKIODwgcra0 YrGUYOjMzWoAKaHhzj7lWzo2Z55BM7jKHXJ5lDU2IJxofBgUXNjXYrrHFXSqfX8V9VlB hJH7lk5H3XjZIG+/kDLgqs9RIrI5YImSRT3X5nl/UJ7OQ3bIr9V2l+lm+upwgj5AYidx xpD+O10KIMKtOorntRGdoZV7ncmISCEobZPCZSOG67O5IL3Fo0BsS5UZHlXSz5djsAIF IqAA== X-Gm-Message-State: ALoCoQlsk0h/Ltnpf2hzyLouT5GKVuPojLpiALDAgdTV5xddP2uwTnRkq/7belLC+tCkrGIFRGyF X-Received: by 10.182.213.166 with SMTP id nt6mr10374921obc.3.1437680114238; Thu, 23 Jul 2015 12:35:14 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.140.89.116 with SMTP id u107ls1146534qgd.96.gmail; Thu, 23 Jul 2015 12:35:13 -0700 (PDT) X-Received: by 10.140.86.105 with SMTP id o96mr216839qgd.11.1437680113407; Thu, 23 Jul 2015 12:35:13 -0700 (PDT) In-Reply-To: <58625b71-98be-4acb-9815-af1ec2113cc6@isocpp.org> X-Original-Sender: vlad.moscow@mail.ru 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:19216 Archived-At: ------=_Part_830_236881370.1437680112775 Content-Type: multipart/alternative; boundary="----=_Part_831_1970079006.1437680112775" ------=_Part_831_1970079006.1437680112775 Content-Type: text/plain; charset=UTF-8 How is it related to std:;pair?! You can with the same success use iterators in any algorithm that do not make a range and what? Do you suggest not to use algorithms? On Thursday, July 23, 2015 at 10:29:23 PM UTC+3, T. C. wrote: > > 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. 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How is it related to std:;pair?! You can with the same suc= cess use iterators in any algorithm that do not make a range and what? Do y= ou suggest not to use algorithms?

On Thursday, July 23, 2015 at 10:2= 9:23 PM UTC+3, T. C. wrote:
Th= ey existed in an earlier C++0x draft, and were removed by that LWG issue be= fore C++11 was published.

Not all pairs of iterators are= ranges. Not even all pairs of iterators returned by functions in the stand= ard library are ranges,
as your own code with minmax_element demo= nstrates.

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:


On Thursday, July 23, 2015 at 2:30:02 PM UTC-4, Vlad from Moscow w= rote:
And one more exampl= e :)

#include <iostream>
#include <uti= lity>
#include <vector>
#include <algorithm>
#inclu= de <iterator>

namespace std
{=C2=A0=C2=A0= =C2=A0
template <class Iterator>
Iterator begin( const std::pa= ir<Iterator, Iterator> &p )
{
=C2=A0=C2=A0=C2=A0 return p.f= irst;
}
template <class Iterator>
Iterator end( const= std::pair<Iterator, Iterator> &p )
{
=C2=A0=C2=A0=C2=A0 re= turn p.second;
}
}
int main()
{
=C2=A0=C2=A0=C2=A0 st= d::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 <&= lt; ' ';
=C2=A0=C2=A0=C2=A0 std::cout << std::endl;
<= div>=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::distance( 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::swap( p.first, p.s= econd );
=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 <&= lt; ' ';
=C2=A0=C2=A0=C2=A0 std::cout << std::endl;
}=C2=A0=C2=A0=C2=A0

The program output is
<= div>
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>
#include &l= t;vector>

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

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

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

}

int main()
{
=C2=A0=C2=A0=C2=A0 s= td::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.begin(), = 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 <&= lt; x << ' ';
=C2=A0=C2=A0=C2=A0 std::cout << std::e= ndl;
}=C2=A0=C2=A0=C2=A0

The progra= m 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 a= t 8:36:46 PM UTC+3, Vlad from Moscow wrote:
I'd like to =C2=A0suggest very simple and=C2= =A0at the same time very useful=C2=A0 overloaded functions std::begin and s= td::end for standard class std::pair.

Here is a de= monstrative program of the idea

#include <iostr= eam>
#include <utility>

namespa= ce 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 <class Iterator>=
Iterator end( const std::pair<Iterator, Iterator> &p )
{=C2=A0=C2=A0=C2=A0 return p.second;
}
}

in= t main()
{
=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::mak= e_pair( 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
=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_pair( 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
<= /blockquote>
<= /blockquote>

--

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