220 40334 <4158f558-6d0c-4b70-9cf2-54afa3d9686d@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: "'Vlad from Moscow' via ISO C++ Standard - Future Proposals" Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: General functions std::reverse and std::sort Date: Fri, 5 Oct 2018 07:51:40 -0700 (PDT) Lines: 804 Approved: news@gmane.org Message-ID: <4158f558-6d0c-4b70-9cf2-54afa3d9686d@isocpp.org> References: <4324d70c-056d-4ff8-beb0-ac3a9b6c4bf9@isocpp.org> <4b93ac1a-4887-430e-a8d4-533680072f45@isocpp.org> <6f5b4526-31d7-4593-b286-34cac63669cb@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_768_1080419618.1538751100822" X-Trace: blaine.gmane.org 1538750978 19026 195.159.176.226 (5 Oct 2018 14:49:38 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 5 Oct 2018 14:49:38 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCXLLRHD7IDRB7PU3XOQKGQE4HW7HSI@isocpp.org Fri Oct 05 16:49:34 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yb1-f200.google.com ([209.85.219.200]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1g8RQ5-0004s0-8m for gclcip-std-proposals@m.gmane.org; Fri, 05 Oct 2018 16:49:33 +0200 Original-Received: by mail-yb1-f200.google.com with SMTP id z14-v6sf6629364ybp.6 for ; Fri, 05 Oct 2018 07:51:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=avdKUkJLml32usfPjSK/c0DO+2etZKkzSyvF2LUo8LY=; b=0zQSvT9oqvMmBg6Yvv18W8MtUJYLCqcXp90KSUOPYyk6O6/7l3r0mAa6bsXagzRHyO hGIaPFNGqRvHpPCMPI1avF4FXOD3jBNEpLaQnVC9bLFBQcS40DbtIz/HPM9XOiVWaful IlnVZ/4Gt4UjFnYM6H2GWlj3AsmzmDmIBzev+1+pL2vYGc+1WwhFHMg/krbJrr1e3MAn v4WQeAFlVx2c636LFdu4EABzjuVCI0GbydKbahT8pdeWZE8gI8v/YivTpXcxMmc1x4C+ XiWPZDMR0sT8yzNvIQv9qVQQJrpi5GXMEVbT1EV1JTFXMhcJQh/5YXMWiQxvj4YrK+vU nJkg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:message-id:in-reply-to:references :subject:mime-version: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=avdKUkJLml32usfPjSK/c0DO+2etZKkzSyvF2LUo8LY=; b=O/emgk+tMhSi5mw8MvpIXbb38tcIizcWl4+YKclX0jv8dVAk0g2D8EKFGtstypBltx ZXow8uUFCbnhA1BMec5fOEeLcaRalNYdCiUieqxjGtehzMKk01wIPD5sQNzBd+CY3q1m 80dTmVfZ0mqVBFnC4sNKpRI8jbnbBlAPiF6qeg4abZIUEkuwtNRgUooZFUdB31WZ38YE HrZX4B4zdle3MqYbYUlZH4ABKzrxJ1o40XgDrO0tJpMNyd9GYa8hFgB1NLUt8Y6X9PK6 7YZ0f0u+qpFZ3pBTQcV7ws2LBACgForuR1gPBM/nnLsuc3h3LOmdXPWxsTOf6QnvrrTf LMdA== X-Gm-Message-State: ABuFfohJlZD2r2IVuAAtyjNdHN673Ieqm1qi74lI38hWOiZadNjk699Z SoDwgnK2lAqqvn1bBydzMOcRjQ== X-Google-Smtp-Source: ACcGV63ZK9B4Rr0l6vwDh0/AzY0SNl73OAlLENEsIuyxGEb35/67oDfEvnnK8qyxREcJlufR8cFbsw== X-Received: by 2002:a25:d60f:: with SMTP id n15-v6mr6040989ybg.91.1538751103277; Fri, 05 Oct 2018 07:51:43 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 2002:a81:ae21:: with SMTP id m33-v6ls1568149ywh.9.gmail; Fri, 05 Oct 2018 07:51:41 -0700 (PDT) X-Received: by 2002:a81:13d4:: with SMTP id 203-v6mr100375ywt.5.1538751101483; Fri, 05 Oct 2018 07:51:41 -0700 (PDT) In-Reply-To: <6f5b4526-31d7-4593-b286-34cac63669cb@isocpp.org> X-Original-Sender: vlad.moscow@mail.ru X-Original-From: Vlad from Moscow 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:40334 Archived-At: ------=_Part_768_1080419618.1538751100822 Content-Type: multipart/alternative; boundary="----=_Part_769_353947659.1538751100823" ------=_Part_769_353947659.1538751100823 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable It seems using requires expressions it is not difficult to write the=20 general function sort and reverse. I do not know yet requires expressions enough well but the initial=20 implementation an look for example the following way. It can be further=20 elaborated. Here is a demonstrative program #include #include #include #include #include template void sort( Container &container ) requires requires() { &Container::sort; } { std::cout << "sort with requires is called.\n";=20 container.sort(); } template void sort( Container &container ) { std::cout << "sort without requires is called.\n";=20 std::sort( std::begin( container ), std::end( container ) ); } template void reverse( Container &container ) requires requires() { &Container:: reverse; } { std::cout << "reverse with requires is called.\n";=20 container.reverse(); } template void reverse( Container &container ) { std::cout << "reverse without requires is called.\n";=20 std::reverse( std::begin( container ), std::end( container ) ); } int main() { std::forward_list lst =3D { 3, 2, 1 }; =20 for ( const auto &item : lst ) std::cout << item << ' '; std::cout << '\n'; =20 sort( lst ); for ( const auto &item : lst ) std::cout << item << ' '; std::cout << '\n'; reverse( lst ); for ( const auto &item : lst ) std::cout << item << ' '; std::cout << '\n'; std::cout << '\n'; =20 std::vector v =3D { 3, 2, 1 }; for ( const auto &item : v ) std::cout << item << ' '; std::cout << '\n'; =20 sort( v ); for ( const auto &item : v ) std::cout << item << ' '; std::cout << '\n'; reverse( v ); for ( const auto &item : v ) std::cout << item << ' '; std::cout << '\n'; std::cout << '\n'; int a[] =3D { 3, 2, 1 }; =20 for ( const auto &item : a ) std::cout << item << ' '; std::cout << '\n'; =20 sort( a ); for ( const auto &item : a ) std::cout << item << ' '; std::cout << '\n'; reverse( a ); for ( const auto &item : a ) std::cout << item << ' '; std::cout << '\n'; } So I am going to put your attention to this propoisal of general functions= =20 *std::sort* and *std::reverse*. Of course another set of the function sort= =20 should be with a second parameter that specifies the comparison. =20 =D1=87=D0=B5=D1=82=D0=B2=D0=B5=D1=80=D0=B3, 27 =D0=B8=D1=8E=D0=BD=D1=8F 201= 3 =D0=B3., 14:23:48 UTC+4 =D0=BF=D0=BE=D0=BB=D1=8C=D0=B7=D0=BE=D0=B2=D0=B0= =D1=82=D0=B5=D0=BB=D1=8C Vlad from Moscow=20 =D0=BD=D0=B0=D0=BF=D0=B8=D1=81=D0=B0=D0=BB: > > So the task is to write appropriate overloaded functions based on these= =20 > conditions. > > =D1=87=D0=B5=D1=82=D0=B2=D0=B5=D1=80=D0=B3, 27 =D0=B8=D1=8E=D0=BD=D1=8F 2= 013 =D0=B3., 14:10:10 UTC+4 =D0=BF=D0=BE=D0=BB=D1=8C=D0=B7=D0=BE=D0=B2=D0= =B0=D1=82=D0=B5=D0=BB=D1=8C R. Martinho=20 > Fernandes =D0=BD=D0=B0=D0=BF=D0=B8=D1=81=D0=B0=D0=BB: > >> On Thu, Jun 27, 2013 at 12:07 PM, Vlad from Moscow =20 >> wrote:=20 >> > Your ideas are different than mine. So they do not contradict each=20 >> other. I=20 >> > want to have general functions sort and reverse even for classes that= =20 >> have=20 >> > no iterators. The only condition they must satisfy is the presence of= =20 >> their=20 >> > own member functions sort and reverse.=20 >> > For the demontsrative example I selected the approach used for=20 >> std:;swap=20 >> > that only to illustrate the idea. However it would be better to write= =20 >> these=20 >> > functions based on conditions=20 >> >=20 >> > std::is_member_function_pointer::value= =20 >> > std::is_member_function_pointer::value=20 >> >=20 >> >> The conditions you want are whether or not=20 >> `decltype(std::declval().reverse())` and=20 >> `decltype(std::declval().sort())` cause substitution=20 >> failures.=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. To view this discussion on the web visit https://groups.google.com/a/isocpp= ..org/d/msgid/std-proposals/4158f558-6d0c-4b70-9cf2-54afa3d9686d%40isocpp.or= g. ------=_Part_769_353947659.1538751100823 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
It seems using requires expressions it is not difficult to= write the general function sort and reverse.

I do not k= now yet requires expressions enough well but the initial implementation an = look for example the following way. It can be further elaborated.

Here is a demonstrative program

#include= <iostream>

#include <forward_list>
#include <vector>
#include <iterator>
#include <algorithm>


template <typename Co= ntainer>= ;
void sort( Container &container ) requires requires() {<= /span> &Container::sort; }
{
=C2= =A0 =C2=A0 std::cout= <<<= /span> "sort with requ= ires is called.\n";
=C2=A0 =C2=A0 container.sort();
}


<= /span>template <typename Container>
void sort( Cont= ainer &container )
{
=C2=A0 =C2=A0 std::cout << "sort without requires is called.\n";
=C2=A0 =C2=A0 std::sort( std::begin( container ), std::<= /span>end<= span style=3D"color: #660;" class=3D"styled-by-prettify">( container ) );
}


template = <typena= me = Container<= span style=3D"color: #660;" class=3D"styled-by-prettify">>
void reverse( Container &container ) re= quires requires() { &Container::reverse; }
{
=C2=A0 = =C2=A0 std= ::cout << "reverse with requi= res is called.\n";
=C2=A0 =C2=A0 container.reverse();
}


<= /span>template <typename Container>
void reverse( C= ontainer <= /span>&container )
{
=C2=A0 =C2=A0 std::cout << "reverse without requires is called.\n";
=C2=A0 =C2=A0 st= d::= reverse( std::begin( container ), std::en= d(<= span style=3D"color: #000;" class=3D"styled-by-prettify"> container = ) );
}


int main()<= br>{
=C2=A0 =C2= =A0 std::<= /span>forward_lis= t<int&g= t; lst =3D { 3, 2, 1 };
=C2=A0 =C2=A0
=C2=A0 =C2=A0 for ( const auto &<= span style=3D"color: #000;" class=3D"styled-by-prettify">item : lst ) std::cout << item << ' = ';
=C2=A0 =C2= =A0 std::<= /span>cout <<<= span style=3D"color: #000;" class=3D"styled-by-prettify"> '\n';
=C2=A0 =C2=A0
=C2=A0 =C2= =A0 sort(<= /span> lst );


=C2=A0 =C2= =A0 for ( const auto &item : lst <= span style=3D"color: #660;" class=3D"styled-by-prettify">) std::cout << item << ' ';
=C2=A0 =C2=A0 std::cout << '\= n';


= =C2=A0 =C2=A0 reverse( lst );<= /span>


=C2=A0 =C2=A0 for ( const auto &item : lst = ) std::cout << item << ' ';
=C2=A0 =C2=A0 std::cout << '\n';


=C2=A0 =C2=A0 std::cout << '\n';
= =C2=A0 =C2=A0
=C2=A0 =C2=A0 std::vector<int> v =3D= {<= span style=3D"color: #000;" class=3D"styled-by-prettify"> 3, 2, 1 };


=C2=A0 =C2=A0 for ( const auto &= ;item : v ) std::cout << item << ' ';
= =C2=A0 =C2=A0 std::c= out <&l= t; = '\n';
=C2=A0 =C2=A0
= =C2=A0 =C2=A0 sort( = v );


=C2= =A0 =C2=A0 for ( const auto &item : v <= /span>) std::cout << item << ' ';
=C2=A0 =C2=A0 std::cout << = '\n';

=C2=A0 =C2=A0 reverse( v = );

=
=C2=A0 =C2=A0 for (= const auto &item : v ) std::cout << item << ' ';
=C2=A0 =C2=A0 std::cout << '\n';

=C2=A0 =C2=A0 std::cout << '\n&= #39;;


=C2= =A0 =C2=A0 int a[] =3D { 3, = 2, 1 };
=C2=A0 =C2=A0
=C2=A0 =C2=A0 for ( c= onst auto &item : a ) std::co= ut <<= ; item << ' ';
=C2=A0 =C2=A0 std::cout << '\n';
=C2=A0 =C2=A0
=C2=A0 =C2=A0 sort( a );


=C2=A0 =C2=A0 for ( const auto &item : a ) std::cout << item << = ' '= ;;<= span style=3D"color: #000;" class=3D"styled-by-prettify">
=C2=A0 =C2=A0 = std::cout << '\n';


=C2=A0 =C2=A0 reverse( a );


=C2=A0 =C2=A0 for ( const auto &item <= span style=3D"color: #660;" class=3D"styled-by-prettify">: a ) std::cout << item << '= ; ';
=C2=A0 = =C2=A0 std= ::cout << '\n';
}


So I am going to put your attention to this propoisal of general functions= std::sort and std::reverse. Of course another set of the fun= ction sort should be with a second parameter that specifies the comparison.=
=C2=A0

=D1=87=D0=B5=D1=82=D0=B2=D0=B5=D1=80=D0=B3, 27 =D0= =B8=D1=8E=D0=BD=D1=8F 2013 =D0=B3., 14:23:48 UTC+4 =D0=BF=D0=BE=D0=BB=D1=8C= =D0=B7=D0=BE=D0=B2=D0=B0=D1=82=D0=B5=D0=BB=D1=8C Vlad from Moscow =D0=BD=D0= =B0=D0=BF=D0=B8=D1=81=D0=B0=D0=BB:
So the task is to write appropriate overloaded functions based o= n these conditions.

=D1=87=D0=B5=D1=82=D0=B2=D0=B5=D1=80=D0= =B3, 27 =D0=B8=D1=8E=D0=BD=D1=8F 2013=C2=A0=D0=B3., 14:10:10 UTC+4 =D0=BF= =D0=BE=D0=BB=D1=8C=D0=B7=D0=BE=D0=B2=D0=B0=D1=82=D0=B5=D0=BB=D1=8C R. Marti= nho Fernandes =D0=BD=D0=B0=D0=BF=D0=B8=D1=81=D0=B0=D0=BB:
On Thu, Jun 27, 2013 at 12:07 PM, Vlad from Moscow <vlad....@mai= l.ru> wrote:
> Your ideas are different than mine. So they do not contradict each= other. I
> want to have general functions sort and reverse even for classes t= hat have
> no iterators. The only condition they must satisfy is the presence= of =C2=A0their
> own member functions sort and reverse.
> For the demontsrative example I selected the approach used for std= :;swap
> that only to illustrate the idea. However it would be better to wr= ite these
> functions based on conditions
>
> std::is_member_function_pointer<decltype( &Container::= reverse)>::value
> std::is_member_function_pointer<decltype( &Container::= sort)>::value
>

The conditions you want are whether or not
`decltype(std::declval<Container>().reverse())` and
`decltype(std::declval<Container>().sort())` cause substitut= ion
failures.

--
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.
To view this discussion on the web visit https://groups.google.= com/a/isocpp.org/d/msgid/std-proposals/4158f558-6d0c-4b70-9cf2-54afa3d9686d= %40isocpp.org.
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