220 17663 article Path: news.gmane.org!not-for-mail From: Vlad from Moscow Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Overloading the family of minmax algorithms Date: Fri, 1 May 2015 07:43:43 -0700 (PDT) Lines: 176 Approved: news@gmane.org Message-ID: References: <558876f0-141f-49ca-bece-7215ec173d1d@isocpp.org> <4A07A10E-B668-447F-A6FA-776D6C3BD7D5@gmail.com> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_1087_1086688575.1430491423174" X-Trace: ger.gmane.org 1430491428 23458 80.91.229.3 (1 May 2015 14:43:48 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 1 May 2015 14:43:48 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCXLLRHD7IDRBIFCR2VAKGQEGK6JTSQ@isocpp.org Fri May 01 16:43:48 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-qk0-f197.google.com ([209.85.220.197]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1YoCAL-0004A3-NV for gclcip-std-proposals@m.gmane.org; Fri, 01 May 2015 16:43:45 +0200 Original-Received: by qkac3 with SMTP id c3sf68531563qka.0 for ; Fri, 01 May 2015 07:43:44 -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:message-id:in-reply-to:references :subject:mime-version:content-type:x-original-sender:reply-to :precedence:mailing-list:list-id:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=aokVTQYSCIuEU0gDiNHDMpiFwa7mzQLtq7MmZKgzdxQ=; b=HqELsCZm8AMZ0u9aDntG40HqmCepl9KL+1bbUns2rpYVP+eQgmAoSfUuRl4ufG+jRc KXUeiXDWWDaxVnPps8+EgbDBahcY7tOF5IRwoXEVIek7vPEHgxDZoI9VlywxXFxsZV7T L50I1uu7+tYOLh5uDBhQ39NXCpWZ9GUD4M+TOgZ3d81+1VGWCEjgD4lLuigU5i/dnaRr aOj1MLnAUFmYkpnbIAC7zGv8cHlahTlx3+vYI0Juvkfm4RZRgvBNZoxVJHFF+dAGO3k/ ud1s930pBqYE11d8yXOmsl+LBwM0/gyJNZt8cy1VBMiiuu1SjU9CU7WEUu0m9qRJ5yem dWWQ== X-Gm-Message-State: ALoCoQniR0rI8x8qNAMkYrdG6MjZDqtN9iODW1lVltyMJQbRMFohzpcjJXnbzw/fg4UrP2Cj5wY1 X-Received: by 10.140.132.73 with SMTP id 70mr16567580qhe.6.1430491424463; Fri, 01 May 2015 07:43:44 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.140.41.169 with SMTP id z38ls1576097qgz.54.gmail; Fri, 01 May 2015 07:43:43 -0700 (PDT) X-Received: by 10.140.93.14 with SMTP id c14mr106392qge.42.1430491423832; Fri, 01 May 2015 07:43:43 -0700 (PDT) In-Reply-To: <4A07A10E-B668-447F-A6FA-776D6C3BD7D5@gmail.com> 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-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:17663 Archived-At: ------=_Part_1087_1086688575.1430491423174 Content-Type: multipart/alternative; boundary="----=_Part_1088_1773945937.1430491423174" ------=_Part_1088_1773945937.1430491423174 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Friday, May 1, 2015 at 5:11:11 PM UTC+3, David Krauss wrote: > > > On 2015=E2=80=9305=E2=80=9301, at 9:47 PM, Vlad from Moscow > wrote: > > A natural question arises how to apply the algorithm that to find for=20 > example the first and last minimum elements or the first and last maximum= =20 > elements in the given sequence? > > This task othen occurs in practice.=20 > > > In practice of what? ;) > > In the practice of programming.=20 > 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. > > It looks bad. It introduces a new name when it is not required and the=20 algorithm I proposed does not imply that only predicates I showed are used.= =20 So my algorithm is very flexible In fact it does not mean for example that= =20 the first and last minimum elements are searched It is simply a partial=20 case of using the algorithm. > In this case to find for example the first and last minimum elements for= =20 > the given sequence it is enough to write > > auto p =3D ::minmax_element( std::begin( a ), std::end( a ), > std::make_pair( std::less<>(),=20 > std::greater<>() ) ); > > Or to find for example the first and last maximum elements for the given= =20 > sequence it is enough to write > > auto p =3D ::minmax_element( std::begin( a ), std::end( a ), > std::make_pair( std::greater<>(),=20 > std::less<>() ) ); > > > It=E2=80=99s far from clear which of these is which. > It is enough clear because the algorithm is named minmax. So there is no=20 difference between the order of iterators in the return pair and the order= =20 of comparators in the parameter of type pair.=20 --=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/. ------=_Part_1088_1773945937.1430491423174 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable


On Friday, May 1, 2015 at 5:11:11 PM UTC+3, David = Krauss wrote:

On 2015=E2=80=9305=E2=80= =9301, at 9:47 PM, Vlad from Moscow <vlad....@mail.ru> wrote:

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

This&= nbsp;task othen occurs in practice.

In practice of what? ;)

In the practice of programming. 
template <class ForwardIterator, c= lass Compare1, class Compare2>
std::pair<ForwardIterator, F= orwardIterator>
minmax_element( ForwardIterator first,
 &nbs= p;            &= nbsp; ForwardIterator last,
       &n= bsp;        std::pair<Compare1, Compa= re2> comp );

Is there = another application of this template? Why not

template <class ForwardIterator, class Compare =3D less<> >
pair<ForwardIterator, ForwardIterator>=
firstlast_min_element( ForwardIterator first, 
    &n= bsp;                  ForwardI= terator last,
      =                  Compare comp = =3D {} );

This only needs one comparator and as li= ttle as half the comparisons.

It loo= ks bad. It introduces a new name when it is not required and the algor= ithm I proposed does not imply that only predicates I showed = ;are used. So my algorithm is very flexible  In fact it does not = mean for example that the first and last minimum elements are searched = ;It is simply a partial case of using the algorithm.
In this case to find for example the f= irst and last minimum elements for the given sequence it is enough to write=

    auto p =3D ::minmax_element( s= td::begin( a ), std::end( a ),
       = ;            &n= bsp;           std::make_= pair( std::less<>(), std::greater<>() ) );

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

    aut= o p =3D ::minmax_element( std::begin( a ), std::end( a ),
  &n= bsp;            = ;            &n= bsp;   std::make_pair( std::greater<>(), std::less<>(= ) ) );

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

It is enough clear because the algorithm is named mi= nmax. So there is no difference between the order of iterators in the retur= n pair and the order of comparators in the parameter of type pair= .. 

--

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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>.
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