220 39244 <67765220-1841-4d05-a797-fa28915cf4eb@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Nicol Bolas Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Standardising a type-erased iterator Date: Fri, 20 Jul 2018 08:31:53 -0700 (PDT) Lines: 92 Approved: news@gmane.org Message-ID: <67765220-1841-4d05-a797-fa28915cf4eb@isocpp.org> References: <09db196a-e818-4d7a-9af1-48f07b2f4c3d@isocpp.org> <904aab35-44dd-4053-91d9-c02cbd4051a0@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_5586_1962646602.1532100713454" X-Trace: blaine.gmane.org 1532100589 7685 195.159.176.226 (20 Jul 2018 15:29:49 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 20 Jul 2018 15:29:49 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCEKFTV6ZUMBB2UAZDNAKGQELLYTA2A@isocpp.org Fri Jul 20 17:29:45 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yw0-f199.google.com ([209.85.161.199]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fgXLk-0001uY-I1 for gclcip-std-proposals@m.gmane.org; Fri, 20 Jul 2018 17:29:44 +0200 Original-Received: by mail-yw0-f199.google.com with SMTP id 133-v6sf6526630ywq.4 for ; Fri, 20 Jul 2018 08:31:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; 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; bh=VbtxRdwi95dVLCS821CyqlXSKFDfgENu8VcY3nzNEI8=; b=Ciw0pei15Obst86t98tR6PvsjtR6OJ1eeAmoaqJK5mePO+/uvdVPrTb+UosxOzaX9P CtXR2yGkYb9aQHc1uKvu1tvkpc+NM43jDuuaCx7Jxqyyv/O171MOD6VLNuMgrsW0+YUv +wojUAVLtmB/jPFKhyhb1FIIJBluDu2HMqmzC9p4RRfJ3N+DZe3DO+PQ5Jx1/TtVyadG FxtLhUb/S+T8X5RPEkJ3W+D1oxCKSL8klAY9hE0RHLnalMdM7qLT/LCVDCszclWwzdMZ CxOMMWQKrzXIh2sLEORWyCRhHY2k8H1jiluraBR6/bNLQ6joenleYDMTxJE7aWLLRlTD QLRg== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; 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; bh=VbtxRdwi95dVLCS821CyqlXSKFDfgENu8VcY3nzNEI8=; b=oCTzWCuv0JevsFyL2KZIMCatZvwEISzEconBqzl26qU/XzJIEqQwk2Rt5p5Qqgz3bE Z1z/oNeqmNnxx76JUlqMKCFPI9n/T0L4MYmXJToUhYdyiLK4wHTJ4R3Ig0VzEs5rlr8c Az3W8CeF3Ld9wl1aojsRxqw8mDastXLCBKLGtUwjJRe95GcnrxDTxc4oCIbuMSf+0Gfr /amHpYqamkcCSVL6hOa8FOc+PCUr/KlJ0W70k4syqFexa/DTnKGl5323DFDNTvD9lZ3H KUJRiU+C+Il9ZtR3owZtfdfvu5+nYPrAAdNxC4RkS1bKi1PXZmKPgF5KNgQ2owHrZmOt Q/OA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:message-id:in-reply-to:references :subject:mime-version: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=VbtxRdwi95dVLCS821CyqlXSKFDfgENu8VcY3nzNEI8=; b=M0V/WOwKzYtpThPiOJWNbLxHjJD5Nzu0nViYSia+KtCV+Fu7zw/YlTFL3W+bmafumf bky+to7ee7CVSzvXq+C6//3AZXZlZAdWrrYQAQo7SV4MnyKF+wmlPqKO8EeRL248bwf9 y/wvU/VuUoC4w3zG5ZHMXhLFeEbTz2aJo1ylXpoa4LjmTdDjANiXFk53uMip7jxURi4C 9KgAI4mWnn6G8VF7FbB7w6H75E7ZLxC/gXx+5AbxUZ90AVgsM9ZHLo0gvWSTqXrfDdYU Y7UlWni4+1cS4xxmcxoO/XhJ1Q2nsMa4hEa2Md07pzwSC9DnU7cxwA6aaIxzICY5SZYQ eW5A== X-Gm-Message-State: AOUpUlFxJLZ+s108mp4a5e099504Tjo1MPMjSSHgqINEjALGcAD+7o1e U0+hXe5ddsMxZmJ3KERgu1ZcvQ== X-Google-Smtp-Source: AAOMgpfOQ5TAlAttNewSfkaOCUxnYOfYolpPYSEq0rBfgXBar3gayC0c4ilLMdWpuJeg8Y96YOIYQw== X-Received: by 2002:a81:6e08:: with SMTP id j8-v6mr683905ywc.149.1532100715186; Fri, 20 Jul 2018 08:31:55 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 2002:a25:8008:: with SMTP id m8-v6ls473150ybk.11.gmail; Fri, 20 Jul 2018 08:31:54 -0700 (PDT) X-Received: by 2002:a25:c5d2:: with SMTP id v201-v6mr73004ybe.4.1532100713982; Fri, 20 Jul 2018 08:31:53 -0700 (PDT) In-Reply-To: X-Original-Sender: jmckesson@gmail.com 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:39244 Archived-At: ------=_Part_5586_1962646602.1532100713454 Content-Type: multipart/alternative; boundary="----=_Part_5587_1760712720.1532100713454" ------=_Part_5587_1760712720.1532100713454 Content-Type: text/plain; charset="UTF-8" On Friday, July 20, 2018 at 9:48:09 AM UTC-4, Thomas Russell wrote: > > I agree that `any_iterator` is more useful than `any_iterator_ref`, and I > also agree that it's likely to do more harm than good. I guess in this case > the symmetry with `function` should be broken because of use-cases. > > I mention `any_range` and a potential `any_sentinel` in the draft > proposal, I do not think it is possible to have a standalone sentinel for > any_iterator, it would have to rely on a type-erased range. > > I think that `any_iterator` is independent enough to be considered alone, > and intend to write a proposal for `any_range` after this, with > `any_iterator` as a dependency. > > Do you think this would be a good strategy > `any_range` makes too much sense to not include in the proposal. C++ is (slowly) moving towards considering ranges as being fundamental constructs, so if `any_iterator` makes sense, so too does `any_range`. I'm not sure if `any_sentinel` is even possible. Especially since it is the sentinel type which determines (statically) which iterators it can be sentinel's for. And you can't enumerate that list of iterator types, since the iterator itself could be a template. For example, iostreams could reasonably have a `stream_sentinel` that works for *all* `istream_iterator`s. As part of `any_range`, it would be possible to pass an iterator/sentinel pair and have the system erase both. -- 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. To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/67765220-1841-4d05-a797-fa28915cf4eb%40isocpp.org. ------=_Part_5587_1760712720.1532100713454 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
On Friday, July 20, 2018 at 9:48:09 AM UTC-4, Thomas Russe= ll wrote:
I agree that `any_ite= rator` is more useful than `any_iterator_ref`, and I also agree that it'= ;s likely to do more harm than good. I guess in this case the symmetry with= `function` should be broken because of use-cases.

I mention `any_range` = and a potential `any_sentinel` in the draft proposal, I do not think it is = possible to have a standalone sentinel for any_iterator, it would have to r= ely on a type-erased range.

I think that `any_iterator` is independen= t enough to be considered alone, and intend to write a proposal for `any_ra= nge` after this, with `any_iterator` as a dependency.

Do you think th= is would be a good strategy


`any_range`= makes too much sense to not include in the proposal. C++ is (slowly) movin= g towards considering ranges as being fundamental constructs, so if `any_it= erator` makes sense, so too does `any_range`.

I= 9;m not sure if `any_sentinel` is even possible. Especially since it is the= sentinel type which determines (statically) which iterators it can be sent= inel's for. And you can't enumerate that list of iterator types, si= nce the iterator itself could be a template. For example, iostreams could r= easonably have a `stream_sentinel` that works for all `istream_itera= tor<T>`s.

As part of `any_range`, it would b= e possible to pass an iterator/sentinel pair and have the system erase both= ..

--
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To post to this group, send email to std-proposals@isocpp.org.
To view this discussion on the web visit https://groups.google.= com/a/isocpp.org/d/msgid/std-proposals/67765220-1841-4d05-a797-fa28915cf4eb= %40isocpp.org.
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