220 19105 <9af8d354-827e-4ca8-b565-6e589f1b09d3@isocpp.org> article Path: news.gmane.org!not-for-mail From: Vlad from Moscow Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Specialization of std::stack for std::forward_list Date: Thu, 16 Jul 2015 08:40:21 -0700 (PDT) Lines: 190 Approved: news@gmane.org Message-ID: <9af8d354-827e-4ca8-b565-6e589f1b09d3@isocpp.org> References: <7f1a222e-5ba7-46dd-9a03-3be94e144e3f@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_176_828721028.1437061221372" X-Trace: ger.gmane.org 1437061226 452 80.91.229.3 (16 Jul 2015 15:40:26 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 16 Jul 2015 15:40:26 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCXLLRHD7IDRBZVAT6WQKGQEJVL5FDQ@isocpp.org Thu Jul 16 17:40:25 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ig0-f198.google.com ([209.85.213.198]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ZFlGq-0000Bu-3J for gclcip-std-proposals@m.gmane.org; Thu, 16 Jul 2015 17:40:24 +0200 Original-Received: by igczg2 with SMTP id zg2sf27992206igc.3 for ; Thu, 16 Jul 2015 08:40:23 -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:x-spam-checked-in-group:list-post :list-help:list-archive:list-subscribe:list-unsubscribe; bh=bzyF1WIcaD8aQSJzBfZlBix/dRBL4Ha38h9pTMok2sg=; b=IBIYdZwLQLtls201YFU+GiTilNnrKBv4MVhQQaV/EA/2xt0vcenWUQq+W5hCmQHFY8 HdPDYhuQQrzUyKnoWnDxcRj+zjoeHLG3sMTpkWidsOKdBgmYTK2r2dqZXZvuJRXdOUEo Vzo7X3oQxMh37OuJOgDDlCt9Soc6sQbszLYbsAe1D/AyXUl0bE17N4u9/+lVCkooPzAT 8kuSzwNJWdXeYDQorqZ6Dm/KHfGFibp0BjVixEbc07OxaSsyjttQ6Z7nWSdky0elWfmo AliwSs4NRPye2EdIiKhTbn1ky+YOI7TizrMCznFESVFU25m2meB1UTHD8itMeV5vERiI tOuA== X-Gm-Message-State: ALoCoQkkiWqB5UVq4r00sMdWRIYC3bbod9KKWDNdml4mquw2k3CHDpPT+mxDbphA9hFOhWrND/TI X-Received: by 10.50.17.10 with SMTP id k10mr4579665igd.8.1437061222962; Thu, 16 Jul 2015 08:40:22 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.140.94.70 with SMTP id f64ls1501230qge.86.gmail; Thu, 16 Jul 2015 08:40:21 -0700 (PDT) X-Received: by 10.140.25.211 with SMTP id 77mr226885qgt.41.1437061221912; Thu, 16 Jul 2015 08:40:21 -0700 (PDT) In-Reply-To: <7f1a222e-5ba7-46dd-9a03-3be94e144e3f@isocpp.org> 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-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:19105 Archived-At: ------=_Part_176_828721028.1437061221372 Content-Type: multipart/alternative; boundary="----=_Part_177_387236219.1437061221372" ------=_Part_177_387236219.1437061221372 Content-Type: text/plain; charset=UTF-8 On Thursday, July 16, 2015 at 6:05:47 PM UTC+3, Sasha Unknown wrote: > > From point of view of pure logic, standard STL-supplied singly linked list > MUST be able to act as underlying implementation of standard STL-supplied > stack (as singly linked list is one of theoretically best ways to do stack). > When I noticed that std::forward_list was added in c++11, my first thought > was: "Oh! They did a great mistake! They had to add std::backward_list > instead! As it's more natural to push/pop at the end, and std::stack > requires it." > But on the other hand, Magnus Fromreide IS RIGHT that "it would be a > strange beast indeed as it won't support insert(iterator, value), > erase(iterator), begin() or end() (but rbegin() and rend())". > > So, my conclusion is: > > 1. > Don't add specialization std::stack>. As it would > be quite unexpected to see front being used in case when with other > containers back is being used. > You are dealing with a stack not with lists. And the stack has a predictable behaviour. It is your choice what underlaying container to use. In any case it is hidden from the user. > 2. > Don't add std::backward_list: as std::forward_list is already > standardized, and per written by Magnus Fromreide. > > Nobody is going to add std::backward_list. However a single linked list that allows to add elements to the tail is obviously needed. And I sugessted such a list somewhere here. > 3. > Add new adapter template class std::reverse_container BaseContainer>. > It would be able to work as std::stack std::reverse_container>>, unless user will try to > access std::stack::size. However, nowhere in documentation should be stated > that it is for tying std::forward_list and std::stack together. It's just > general purpose adapter. > It tries to publish all STL-stereotypical direction-neutral members of > BaseContainer, and to reverse all STL-stereotypical direction-sensitive > members of BaseContainer (with using std::reverse_iterator when needed). > Accessing a member of std::reverse_container that doesn't > have counterpart in BaseContainer causes template instantiation error. But > otherwise it is ok to use std::reverse_container with BaseContainer that > doesn't have all of STL-stereotypical members. > > Insetad of make the life easier you are trying to make the life harder. > 4. > Either add std::forward_list::size member that must act identically to > std::list::size. > Or mark std::list::size member as obsolete/discouraged in documentation. > Because the decision should be the same for std::list and > std::forward_list (at least, I see no reason for different decision on > std::forward_list::size and std::list::size). > > The specialization of std::stack for std:;forward_list may have not data member size. But all specializations of std::stack shall have method clear that I also proposed. Cheers. > > On Friday, September 6, 2013 at 8:37:38 PM UTC+3, Vlad from Moscow wrote: >> >> I would like to propose to include specialization of std::stack for >> std::forward_list. >> >> In fact std::forward_list has already all characteristics of a stack. >> There will be only one difference compared with the primary class >> std::stack: the specialization will not contain member function size() >> because std::forward_list has no such member. >> >> What will you say? >> > -- --- 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 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/. ------=_Part_177_387236219.1437061221372 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable

On Thursday, July 16, 2015 at 6:05:47 PM UTC+3, Sasha Unknown wrote= :
From point of view of pure l= ogic, standard STL-supplied singly linked list MUST be able to act as under= lying implementation of standard STL-supplied stack (as singly linked list = is one of theoretically best ways to do stack).
When I noticed that std= ::forward_list was added in c++11, my first thought was: "Oh! They did= a great mistake! They had to add std::backward_list instead! As it's m= ore natural to push/pop at the end, and std::stack requires it."
Bu= t on the other hand, Magnus Fromreide IS RIGHT that "it would be a str= ange beast indeed as it won't support insert(iterator, value), erase(it= erator), begin() or end() (but rbegin() and rend())".

So, my co= nclusion is:

1.
Don't add specialization std::stack<T, std= ::forward_list<T>>. As it would be quite unexpected to see front b= eing used in case when with other containers back is being used.
<= /blockquote>

You are dealing with a stack not with lists= .. And the stack has a predictable behaviour. It is your choice what underla= ying container to use. In any case it is hidden from the user. =C2=A0
=
=C2=A0
2.
Don= 9;t add std::backward_list: as std::forward_list is already standardized, a= nd per written by Magnus Fromreide.

Nobody i= s=C2=A0going to add std::backward_list. However a single linked list that a= llows to add elements to the tail is obviously needed. And I sugessted such= a list somewhere here.
=C2=A0
=
3.
Add new adapter template class std::reverse_containe= r<typename BaseContainer>.
It would be able to work as std::stack&= lt;T, std::reverse_container<std::forward_list<T>>>, unless = user will try to access std::stack::size. However, nowhere in documentation= should be stated that it is for tying std::forward_list and std::stack tog= ether. It's just general purpose adapter.
It tries to publish all STL-stereotypical direction-neutral members of Base= Container, and to reverse all STL-stereotypical direction-sensitive members= of BaseContainer (with using std::reverse_iterator when needed). Accessin= g a member of std::reverse_container<BaseContainer> that doesn't = have counterpart in BaseContainer causes template instantiation error. But = otherwise it is ok to use std::reverse_container with BaseContainer that do= esn't have all of STL-stereotypical members.

=
Insetad of make the life easier you are trying=C2=A0to make the life h= arder.
=C2=A0
= 4.
Either add std::forward_list::size member that must act identically t= o std::list::size.
Or mark std::list::size member as obsolete/discourage= d in documentation.
Because the decision should be the same for std::lis= t and std::forward_list (at least, I see no reason for different decision o= n std::forward_list::size and std::list::size).

<= div>The specialization of std::stack for std:;forward_list may have not dat= a member=C2=A0=C2=A0size. But all specializations of std::stack shall have = method clear that I also proposed.

Cheers.

On Friday, September 6, 2013 at 8:= 37:38 PM UTC+3, Vlad from Moscow wrote:
I would like to propose to include specialization of std::st= ack for std::forward_list.
=C2=A0
In fact std::forward= _list has already all characteristics of a stack. There will be only one di= fference compared with the primary class std::stack:=C2=A0 the specializati= on will not contain member function size() because std::forward_list has no= such member.
=C2=A0
What will you say?

--

---
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.
Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposals/<= /a>.
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