220 22101 <3696ecfa-9960-493d-94b7-b15390d0c396@isocpp.org> article Path: news.gmane.org!not-for-mail From: Evan Teran Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: string view constructed from iterator pair? Date: Thu, 29 Oct 2015 10:07:42 -0700 (PDT) Lines: 107 Approved: news@gmane.org Message-ID: <3696ecfa-9960-493d-94b7-b15390d0c396@isocpp.org> References: <476bb7a8-15ec-4f9c-a295-592495de3a86@isocpp.org> <0fdef179-8304-40fb-bc94-48d908e779d0@isocpp.org> <5ee68d17-bb78-4bb7-8ff4-994f1016a0ad@isocpp.org> <78099cf0-3d5a-4531-99e4-03ea92e83455@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_615_2098889785.1446138462540" X-Trace: ger.gmane.org 1446138470 25577 80.91.229.3 (29 Oct 2015 17:07:50 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 29 Oct 2015 17:07:50 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCDNZQVEQMLRBX5EZGYQKGQEH6BWUVQ@isocpp.org Thu Oct 29 18:07:45 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-vk0-f71.google.com ([209.85.213.71]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Zrqfw-00018S-Dk for gclcip-std-proposals@m.gmane.org; Thu, 29 Oct 2015 18:07:44 +0100 Original-Received: by vkgy127 with SMTP id y127sf60928231vkg.2 for ; Thu, 29 Oct 2015 10:07:43 -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 :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=Mr2uwWMr9ggoVBQKlVwyeRxW8AvYM0WZshdXXQafZZ0=; b=ChwO9Vf2n9Wfxk7BqaZS3b34+vxlhtJzzmj8teNDBZBB+mdu6C98sIcPlNLN5clAoW tRvhQkiInFQxOyDwnDfiXDb94ffT1/67lI19EBA3YGNnSMR4MIH1UGLBeTdVGKtjUSRc LJZX7lLqsK+JwoQdeyPv8EmEhzUxGAUPvXQUzHVO+p5BtuWwfv4Wdsm2naOZf8Q3E0KS Y+nhj65JsaMtTPVKUWns1pqfROstKIaWEQk/j5jZLD4JjOfAMQCk7wl5ZT2XOi0gUY6N oT7sM57EIKdj7K+yHce/67yRt3NL7wJ/9pNIg8Nhk0ZonpsK1RYNlrcr95jeMQo2V5S8 sRBg== 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=Mr2uwWMr9ggoVBQKlVwyeRxW8AvYM0WZshdXXQafZZ0=; b=gjmfntSMRZoJrJKnHYhgxSXxNb6hah0/pyeQTSxVcNzK9PDpMMP/D4oIg8P7l1xLnq +4TyXb7itjuc1e65pvvoBaluRbHRmsRPm7SJy/HWJu20YIJbhLMKuHTOQUsHMnHHJp5S jdg/8jcg7wB5LIrk20y5iaqBj5z1BTMOskB1G8ilT5kc659XF6DSgTJ1ViAzfXj9nQ0x oDWGHcBkgcTS/9HOTYJ1k7m9ByxM5SgTX8z1Kq7PfLQtBGuMXAlze8Q1/QSuymE/EeCk o8pMPr0irqDUaSR66/ytZZ8MgIYmZ+EFtg9K368eMXtDHsnFj1Xc9/INpbcZv3Z3bVuM PcIg== X-Gm-Message-State: ALoCoQnd+uhLPvvumJ0CS0JYoxo4Eq4Lj8qbgm+LA0/JKakScI5tAE/IP+kxvDFmXW289jezFjy9 X-Received: by 10.129.82.193 with SMTP id g184mr2308287ywb.44.1446138463801; Thu, 29 Oct 2015 10:07:43 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.19.207 with SMTP id 76ls337869iot.4.gmail; Thu, 29 Oct 2015 10:07:43 -0700 (PDT) X-Received: by 10.50.131.196 with SMTP id oo4mr306393igb.5.1446138463026; Thu, 29 Oct 2015 10:07:43 -0700 (PDT) In-Reply-To: <78099cf0-3d5a-4531-99e4-03ea92e83455@isocpp.org> X-Original-Sender: evan.teran@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:22101 Archived-At: ------=_Part_615_2098889785.1446138462540 Content-Type: multipart/alternative; boundary="----=_Part_616_1178035029.1446138462553" ------=_Part_616_1178035029.1446138462553 Content-Type: text/plain; charset=UTF-8 Fair enough. Regarding the contiguous and ordering issues, personally, I file them under the "give the function bad input, get UB" category, but I agree that it's a real concern. If too many inputs result in UB, then it's too easy to misuse or abuse. I think that is enough to make this a non-starter. That being said, I actually like the "make_string_view" idea, which could have overloads for the various things that we know will work. I have another thought on string_views, but it's mostly unrelated, so I'll make that a separate post. Thanks for the feedback. On Thursday, October 29, 2015 at 12:54:29 PM UTC-4, Nicol Bolas wrote: > > On Thursday, October 29, 2015 at 12:24:33 PM UTC-4, Brent Friedman wrote: >> >> Evan, >> >> Yes that does address the issue I was raising. Of course, if strings and >> vectors used pointer iterators then we wouldn't need the if test or the >> overload at all. >> > > Even if those two types use pointer iterators, that shouldn't mean that > contiguous iterators *ought* to be pointers. What about range adaptors? > Some of those can be contiguous iterators, but they're certainly not > pointers. > > Of course, you wouldn't be able to use range adaptors in string_views > either. They're more for template code. So there's another strike against > this overload. `string_view` is meant for arrays of characters, which in > C++ is specified by pointers. > > Ultimately, what you want isn't for std::string and std::vector iterators > to be pointers. You want them to be *convertible* to pointers (and > vice-versa). > -- --- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. 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Fair enough. Regarding the contiguous and o= rdering issues, personally, I file them under the "give the function b= ad input, get UB" category, but I agree that it's a real concern. = If too many inputs result in UB, then it's too easy to misuse or abuse.= I think that is enough to make this a non-starter.

That= being said, I actually like the "make_string_view" idea, which c= ould have overloads for the various things that we know will work. I have a= nother thought on string_views, but it's mostly unrelated, so I'll = make that a separate post.

Thanks for the feedback= ..

On Thursday, October 29, 2015 at 12:54:29 PM UTC-4, Nicol Bolas wr= ote:
On Thursd= ay, October 29, 2015 at 12:24:33 PM UTC-4, Brent Friedman wrote:
Evan,

Yes = that does address the issue I was raising. Of course, if strings and vector= s used pointer iterators then we wouldn't need the if test or the overl= oad at all.

Even if those two types use po= inter iterators, that shouldn't mean that contiguous iterators ought= to be pointers. What about range adaptors? Some of those can be contig= uous iterators, but they're certainly not pointers.

Of course, y= ou wouldn't be able to use range adaptors in string_views either. They&= #39;re more for template code. So there's another strike against this o= verload. `string_view` is meant for arrays of characters, which in C++ is s= pecified by pointers.

Ultimately, what you want isn't for std::s= tring and std::vector iterators to be pointers. You want them to be conv= ertible to pointers (and vice-versa).

--

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