220 7228 article Path: news.gmane.org!not-for-mail From: =?ISO-8859-1?Q?R=E9my_Lefevre?= Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: "count_while" and "count_until" algorithms Date: Wed, 9 Oct 2013 13:13:44 +0200 Lines: 463 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=089e011777afdbcbf604e84cfc84 X-Trace: ger.gmane.org 1381317269 19395 80.91.229.3 (9 Oct 2013 11:14:29 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 9 Oct 2013 11:14:29 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCN7B34JVEARBEPV2SJAKGQEARJGI7I@isocpp.org Wed Oct 09 13:14:31 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-wg0-f69.google.com ([74.125.82.69]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1VTrik-0005Jw-Qq for gclcip-std-proposals@m.gmane.org; Wed, 09 Oct 2013 13:14:26 +0200 Original-Received: by mail-wg0-f69.google.com with SMTP id f12sf729792wgh.8 for ; Wed, 09 Oct 2013 04:14:26 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=mime-version:in-reply-to:references:from:date:message-id:subject: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:content-type; bh=FwDPne7oxLNOT3B4ZvhAiVvxG+f3lVVLMFVK1MP0jNE=; b=cvS5D2ApZ/dYzW7jttKwW9q0jxpWffJwiJBpdotnkX8HLUMu8zzJbsXsWXCDDRzqgH gVVyIuPdLtaMa2NdP/M26Ddy/sNPlIferhOgR9l1g1Flyf3g2KKgOU2v7ovB7wghZCnB IKH0mfh2gZ2NXF03HcJ4dIhJAD9OinSVwCnE/p6oYcwAduh7UjRdNQFKZsEw47v4pjjY vvtYVT/KwJJsCUTnpxtuC+Jl4dRbEAdtFMIoxpCuG2tFvxGkYQQDsvIDzVIwv7+iwsNr scsxNxsL2/V8Fliw9SLmEg3SK36wbOBQe3h/1H/gtOQZdlfJZNNKpEVoUloKZGpuHSUs 6doQ== X-Received: by 10.180.73.112 with SMTP id k16mr942773wiv.5.1381317265930; Wed, 09 Oct 2013 04:14:25 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.180.91.226 with SMTP id ch2ls1383977wib.30.canary; Wed, 09 Oct 2013 04:14:24 -0700 (PDT) X-Received: by 10.180.13.113 with SMTP id g17mr2218516wic.19.1381317264677; Wed, 09 Oct 2013 04:14:24 -0700 (PDT) Original-Received: from mail-wi0-x231.google.com (mail-wi0-x231.google.com [2a00:1450:400c:c05::231]) by mx.google.com with ESMTPS id cw7si15766424wjc.165.1969.12.31.16.00.00 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 09 Oct 2013 04:14:24 -0700 (PDT) Received-SPF: pass (google.com: domain of lefevreremy@gmail.com designates 2a00:1450:400c:c05::231 as permitted sender) client-ip=2a00:1450:400c:c05::231; Original-Received: by mail-wi0-f177.google.com with SMTP id hq15so742299wib.10 for ; Wed, 09 Oct 2013 04:14:24 -0700 (PDT) X-Received: by 10.194.122.168 with SMTP id lt8mr33835wjb.76.1381317264262; Wed, 09 Oct 2013 04:14:24 -0700 (PDT) Original-Received: by 10.194.192.33 with HTTP; Wed, 9 Oct 2013 04:13:44 -0700 (PDT) In-Reply-To: X-Original-Sender: lefevreremy@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of lefevreremy@gmail.com designates 2a00:1450:400c:c05::231 as permitted sender) smtp.mail=lefevreremy@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:7228 Archived-At: --089e011777afdbcbf604e84cfc84 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Furthermore, the counting_iterator doesn't always work. For example, if find/find_if reaches the end of the range, the behavior is to return the iterator named "last" passed in argument. But this iterator has not been incremented by the algorithm and its counter is set to 0 instead of the distance between first and last, leading to a wrong result. 2013/10/9 R=E9my Lefevre > Good point for a counting iterator ! Unfortunately, the one in boost > library doesn't fit our need here and I am not aware of any counting > iterator in C++14. > > > 2013/10/9 Peter Sommerlad > >> +1 for composability instead of proliferation... >> >> Do we have boost's counting iterator adapter in c++14 or library TS? >> >> Sent from Peter Sommerlad's iPad >> >> On 09.10.2013, at 07:13, "Benjamin Lindley" >> wrote: >> >> What about creating an iterator adapter instead? One which keeps track >> of 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 "count_until". Here are their behavior: >>> >>> template >>> >>> >>> >>> >>> typename iterator_traits**::difference_type >>> >>> >>> >>> >>> count_while (InputIterator first, InputIterator last, UnaryPredicat= e 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, UnaryPredicat= e 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 >>> library ? >>> >> -- >> >> --- >> You received this message because you are subscribed to the Google Group= s >> "ISO C++ Standard - Future Proposals" group. >> To unsubscribe from this group and stop receiving emails from it, send a= n >> email 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-proposals/. >> >> -- >> >> --- >> You received this message because you are subscribed to a topic in the >> Google Groups "ISO C++ Standard - Future Proposals" group. >> To unsubscribe from this topic, visit >> https://groups.google.com/a/isocpp.org/d/topic/std-proposals/bXrQrkBw59c= /unsubscribe >> . >> To unsubscribe from this group and all its topics, send an email 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-proposals/. >> > > --=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/. --089e011777afdbcbf604e84cfc84 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
Furthermore, the counting_iterator doesn't always work= .. For example, if find/find_if reaches the end of the range, the behavior i= s to return the iterator named "last" passed in argument. But thi= s iterator has not been incremented by the algorithm and its counter is set= to 0 instead of the distance between first and last, leading to a wrong re= sult.


2013/10= /9 R=E9my Lefevre <lefevreremy@gmail.com>
Good point for a counting iterator ! Unfortunately, the on= e in boost library doesn't fit our need here and I am not aware of any = counting iterator in C++14.


2013/10/9 Peter Sommerlad <Peter.Sommerlad@hsr.ch>
<= blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px= #ccc solid;padding-left:1ex">
+1 for composability instead of proliferation...

Do we have boost's counting iterator adapter in c= ++14 or library TS?

Sent from Peter Sommerlad's=A0iPad

On 09.10.2013, at 07:13, "Benjamin Lindley" &l= t;benjamesli= ndley@gmail.com> wrote:

What about creating an iterator adapter ins= tead?=A0 One which keeps track of how many times it has been incremented?
typedef std::istream_iterator<int> base_t;
base_t ib(std::cin), ie;
std::counting_iterator<base_t> b(ib),= e(ie);
auto p =3D std::find_if(b, e, pred);
std::cout << p.<= /span>count();

Then you could apply it to other algorithms b= esides 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 "count_until". Here are thei= r behavior:

template <=
class InputIterator, cl=
ass UnaryPre=
dicate>





=A0 typename iterator_traits<<=
span style=3D"color:rgb(102,0,102)">InputIterator>::difference_type





=A0 =A0 count_while (InputIterator first, InputIterator last,=
 UnaryPredicate pr=
ed)





{
=A0 typename iterator_=
traits<InputIterator>::difference_type ret =3D 0;





=A0 while=
 (first!=3Dlast &=
;& pred(*first)) {





=A0 =A0 ++ret;
=A0 =A0 ++first;





=A0 }
=A0 return ret;


}

template <=
class InputIterator, cl=
ass UnaryPre=
dicate>





=A0 typename iterator_traits<<=
span style=3D"color:rgb(102,0,102)">InputIterator>::difference_type





=A0 =A0 count_until (InputIterator first, InputIterator last,=
 UnaryPredicate pr=
ed)





{
=A0 typename iterator_traits&l=
t;InputIterator>::difference_type ret <=
/span>=3D 0;=






=A0 while=
 (first!=3Dlast &=
;& !pred(*first)) =
{





=A0 =A0 ++ret;
=A0 =A0 ++first;





=A0 }
=A0 return ret;

}
<=
/code>

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

--
=A0
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To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposals+unsubscribe@isocpp.org.

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=A0
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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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