220 17662 <4A07A10E-B668-447F-A6FA-776D6C3BD7D5@gmail.com> article Path: news.gmane.org!not-for-mail From: David Krauss Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Overloading the family of minmax algorithms Date: Fri, 1 May 2015 22:10:50 +0800 Lines: 132 Approved: news@gmane.org Message-ID: <4A07A10E-B668-447F-A6FA-776D6C3BD7D5@gmail.com> References: <558876f0-141f-49ca-bece-7215ec173d1d@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 (Mac OS X Mail 8.2 \(2098\)) Content-Type: multipart/alternative; boundary="Apple-Mail=_B0CDF983-15B2-4B05-9F94-BC709AAB0CD0" X-Trace: ger.gmane.org 1430489474 22106 80.91.229.3 (1 May 2015 14:11:14 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 1 May 2015 14:11:14 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCW25A7E3QCRB7USR2VAKGQEKW4W4HY@isocpp.org Fri May 01 16:11:13 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pa0-f70.google.com ([209.85.220.70]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1YoBeq-000547-IE for gclcip-std-proposals@m.gmane.org; Fri, 01 May 2015 16:11:12 +0200 Original-Received: by pavx7 with SMTP id x7sf164928231pav.1 for ; Fri, 01 May 2015 07:11:11 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:content-type:message-id:mime-version :subject:date:references:to:in-reply-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; bh=y7r9aS3MOmCX8wXYBNa9ZSq2VR9AGpJJOCIqg7YHPro=; b=S8YrpQ6IPn3W/S+DZWSSWhorlJHDsUbBjGOmz8B+y/E8h6j3Zul9Gd4s+fNDra8q67 quXw9OOamob6xyUuTHROkD7Oz1DUpC/mhGWgZcWx3WNbn958WaffGE/A+E6G3XoYfMF0 PyisyQLif04/Zv9e4nDrQllgiVumnsADjD/kGHWCk/oMCmunKBNv3n8IZUeyUdmtF8xj ziVEHprxst/v8win5oFMke8j+xaQPBa8xu/2oh4J+geePTFT15kuad31xvu1x9zDzGk1 JSZQc8/Xg9iKHkAc3vlLg9WYaRAtPMHkrkYnMzo1lkpvEIzc81Lj1xTHBVnXTn7CrVY6 LurA== X-Gm-Message-State: ALoCoQktDXudb6ayyEKrZGIewiqQ7qj7CRev0WfRhezWUYXl7R5UeK3valXdpBKCO4AldQaJ1Cjo X-Received: by 10.66.145.225 with SMTP id sx1mr16894649pab.21.1430489471619; Fri, 01 May 2015 07:11:11 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.51.17.3 with SMTP id ga3ls459978igd.20.canary; Fri, 01 May 2015 07:11:10 -0700 (PDT) X-Received: by 10.66.250.131 with SMTP id zc3mr15960449pac.136.1430489470790; Fri, 01 May 2015 07:11:10 -0700 (PDT) Original-Received: from mail-pd0-x22a.google.com (mail-pd0-x22a.google.com. [2607:f8b0:400e:c02::22a]) by mx.google.com with ESMTPS id x16si8174871pdi.8.2015.05.01.07.11.10 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 01 May 2015 07:11:10 -0700 (PDT) Received-SPF: pass (google.com: domain of potswa@gmail.com designates 2607:f8b0:400e:c02::22a as permitted sender) client-ip=2607:f8b0:400e:c02::22a; Original-Received: by pdbnk13 with SMTP id nk13so93324398pdb.0 for ; Fri, 01 May 2015 07:11:10 -0700 (PDT) X-Received: by 10.66.150.196 with SMTP id uk4mr18274039pab.54.1430489470419; Fri, 01 May 2015 07:11:10 -0700 (PDT) Original-Received: from [172.20.10.2] ([121.54.44.91]) by mx.google.com with ESMTPSA id j10sm4997174pdp.83.2015.05.01.07.11.04 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Fri, 01 May 2015 07:11:09 -0700 (PDT) In-Reply-To: <558876f0-141f-49ca-bece-7215ec173d1d@isocpp.org> X-Mailer: Apple Mail (2.2098) X-Original-Sender: potswa@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of potswa@gmail.com designates 2607:f8b0:400e:c02::22a as permitted sender) smtp.mail=potswa@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:17662 Archived-At: --Apple-Mail=_B0CDF983-15B2-4B05-9F94-BC709AAB0CD0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 > On 2015=E2=80=9305=E2=80=9301, at 9:47 PM, Vlad from Moscow wrote: >=20 > A natural question arises how to apply the algorithm that to find for exa= mple the first and last minimum elements or the first and last maximum elem= ents in the given sequence? >=20 > This task othen occurs in practice. In practice of what? ;) > template > std::pair > minmax_element( ForwardIterator first,=20 > ForwardIterator last, > std::pair comp ); Is there another application of this template? Why not template > pair firstlast_min_element( ForwardIterator first,=20 ForwardIterator last, Compare comp =3D {} ); This only needs one comparator and as little as half the comparisons. > In this case to find for example the first and last minimum elements for = the given sequence it is enough to write >=20 > auto p =3D ::minmax_element( std::begin( a ), std::end( a ), > std::make_pair( std::less<>(), std::greate= r<>() ) ); >=20 > Or to find for example the first and last maximum elements for the given = sequence it is enough to write >=20 > auto p =3D ::minmax_element( std::begin( a ), std::end( a ), > std::make_pair( std::greater<>(), std::les= s<>() ) ); It=E2=80=99s far from clear which of these is which. --=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. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposa= ls/. --Apple-Mail=_B0CDF983-15B2-4B05-9F94-BC709AAB0CD0 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=UTF-8
On 2015=E2=80=9305= =E2=80=9301, at 9:47 PM, Vlad from Moscow <vlad.moscow@mail.ru> wrote:

A natural question arises how to apply the algorithm that to fin= d for example the first and last minimum elements or the first and las= t maximum elements in the given sequence?

This task othen occurs in practice.

=
In practice of what? ;)

temp= late <class ForwardIterator, class Compare1, class Compare2>
std::pair<ForwardIterator, ForwardIterator>
minmax_element( ForwardIterator first,
   &= nbsp;            For= wardIterator last,
       =          std::pair<Compare1, Com= pare2> comp );

<= div>Is there another application of this template? Why not

template <class Fo= rwardIterator, class Compare =3D less<> >
pair<ForwardIterator, ForwardIterator>
fir= stlast_min_element( ForwardIterator first, 
   = ;                    Forw= ardIterator last,
 =                     &nbs= p;Compare comp =3D {} );

Thi= s only needs one comparator and as little as half the comparisons.
In this case to find for example the fi= rst and last minimum elements for the given sequence it is enough to write<= /div>

   = ; auto p =3D ::minmax_element( std::begin( a ), std::end( a ),
            &= nbsp;           &nbs= p;      std::make_pair( std::less<>(), std::= greater<>() ) );

Or to find for example the first and last maximum elements for t= he given sequence it is enough to write

    auto p =3D ::minmax_element( std::begin( a ), std::end(= a ),
         &= nbsp;           &nbs= p;         std::make_pair( std::gre= ater<>(), std::less<>() ) );
<= /div>

It=E2=80=99s far from clea= r which of these is which.

--

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