220 7218 article Path: news.gmane.org!not-for-mail From: Benjamin Lindley Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: "count_while" and "count_until" algorithms Date: Tue, 8 Oct 2013 22:13:02 -0700 (PDT) Lines: 307 Approved: news@gmane.org Message-ID: References: Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_1690_26279800.1381295582429" X-Trace: ger.gmane.org 1381295580 13285 80.91.229.3 (9 Oct 2013 05:13:00 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 9 Oct 2013 05:13:00 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDI7THWOWMDRBX6L2OJAKGQEU6E4JDI@isocpp.org Wed Oct 09 07:13:04 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-vc0-f197.google.com ([209.85.220.197]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1VTm52-0000bs-CO for gclcip-std-proposals@m.gmane.org; Wed, 09 Oct 2013 07:13:04 +0200 Original-Received: by mail-vc0-f197.google.com with SMTP id gd11sf638261vcb.4 for ; Tue, 08 Oct 2013 22:13:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; 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 :content-type; bh=fvSFpFPriRscvk6YYRPFzc0aYk7dataB5FQUbtuzLS8=; b=QUbXz5NnIOr4AxwOXEupCDPkCqeoVAH8/u0gNy8sW+1ZVSNDtj402/kS+g5NRL6kzy 1Rh5buvxNAbmsTHoBf8jr2+ApkH0OYnC/9hMr36wqVjgSguIo8j7NVvvRmKnYH3hLxsS 2TVlivqIUhEbPUF4ZO+7h1z7H15/+8CvD1Jsv0K3YrKfS48OdBImPb8v1paiFaLHCtly lO07uj7BzKdjWx+AVSfarsx9F/D+DG7Fs/n3nRinRSUilAz03jMcuDfe575sdSxH9S23 EhqzcL4J0B4W8wBP5WhHXHrC30dgAkJMxtO5O+mBx5inXfJ4D0yNu9IJNCWsGDsYKJTZ yqJw== X-Received: by 10.236.135.211 with SMTP id u59mr4956609yhi.43.1381295583463; Tue, 08 Oct 2013 22:13:03 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.70.228 with SMTP id p4ls503511qeu.43.gmail; Tue, 08 Oct 2013 22:13:02 -0700 (PDT) X-Received: by 10.49.71.34 with SMTP id r2mr8493qeu.14.1381295582876; Tue, 08 Oct 2013 22:13:02 -0700 (PDT) In-Reply-To: X-Original-Sender: benjameslindley@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:7218 Archived-At: ------=_Part_1690_26279800.1381295582429 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable What about creating an iterator adapter instead? One which keeps track of= =20 how many times it has been incremented? typedef std::istream_iterator base_t; base_t ib(std::cin), ie; std::counting_iterator b(ib), e(ie); auto p =3D std::find_if(b, e, pred); std::cout << p.count(); Then you could apply it to other algorithms besides find/find_if. On Tuesday, October 8, 2013 3:04:23 PM UTC-5, R=E9my Lefevre wrote: > > Hi, > > I thought about two new algorithms, that could be named "count_while" and= =20 > "count_until". Here are their behavior: > > template > > > typename iterator_traits::difference_type > > > count_while (InputIterator first, InputIterator last, UnaryPredicate = pred) > > { > typename iterator_traits::difference_type ret =3D 0; > > > while (first!=3Dlast && pred(*first)) { > > > ++ret; > ++first; > > > } > return ret; > > } > > > template > > > typename iterator_traits::difference_type > > > count_until (InputIterator first, InputIterator last, UnaryPredicate = pred) > > { > > typename iterator_traits::difference_type ret =3D 0; > > > while (first!=3Dlast && !pred(*first)) { > > > ++ret; > ++first; > > > } > return ret; > > > } > > > What do you think about adding these two components to the algorithms=20 > library ? > --=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_1690_26279800.1381295582429 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
What about creating an iterator adapter instead?  One= which keeps track of how many times it has been incremented?

<= span style=3D"color: #008;" class=3D"styled-by-prettify">typedef std::istream_iterator<int> base_t;
base_t ib(std::cin), ie;
std= ::counting_iterator<= span style=3D"color: #080;" class=3D"styled-by-prettify"><base_t> b(ib), e(ie);
<= /span>auto= p =3D std::find_if(b,= e,= pred);
std::cout << p.count();=

Then you could apply it to other algorith= ms besides find/find_if.

On Tuesday, October 8, 2013 3:04:23 PM UTC-= 5, R=E9my Lefevre wrote:
Hi,

I thought about two new algorithms, that could be nam= ed "count_while" and "count_until". Here are their behavior:

template <class<=
/var> InputIterator, class UnaryPredicate>


  typename=
 iterator_traits<InputIter=
ator>::difference_type


    count_while (InputIterator first, InputIterator last,<=
/span> UnaryPredicate pred=
)


{
  typenam=
e iterator_traits<InputIterator>::difference_type ret =3D 0;


  while =
(first!=3Dlast && <=
/var>pred(*first)) {


    ++ret;
    ++first;


  }
  =
return ret;


}

template <class<=
/var> InputIterator, class UnaryPredicate>


  typename=
 iterator_traits<InputIter=
ator>::difference_type


    count_until (InputIterator first, InputIterator last,<=
/span> UnaryPredicate pred=
)


{
  typename iterator_traits<InputIterator=
>::difference_type ret =3D 0;


  while =
(first!=3Dlast && <=
/var>!pred(*first)) {


    ++ret;
    ++first;


  }
  =
return ret;


}

What do you think about adding these two components to the algorithms l= ibrary ?

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