220 33842 article Path: news.gmane.org!.POSTED!not-for-mail From: Nevin Liber Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: string_view for fstream::open() Date: Fri, 11 Aug 2017 14:46:40 -0500 Lines: 72 Approved: news@gmane.org Message-ID: References: <3456831.gsseCm4DuK@tjmaciei-mobl1> <6240d6af-a518-4788-a56f-b7d0c8976dc4@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="94eb2c11972ad90aec05567f94b4" X-Trace: blaine.gmane.org 1502480845 5140 195.159.176.226 (11 Aug 2017 19:47:25 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 11 Aug 2017 19:47:25 +0000 (UTC) To: "std-proposals@isocpp.org" Original-X-From: std-proposals+bncBCE35H5S6IDBBSUTXDGAKGQE4UEO6GA@isocpp.org Fri Aug 11 21:47:20 2017 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 1dgFtt-0000oW-Cj for gclcip-std-proposals@m.gmane.org; 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[2607:f8b0:400e:c05::236]) by mx.google.com with ESMTPS id i12si880183pgc.831.2017.08.11.12.47.22 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 11 Aug 2017 12:47:22 -0700 (PDT) Received-SPF: pass (google.com: domain of nliber@gmail.com designates 2607:f8b0:400e:c05::236 as permitted sender) client-ip=2607:f8b0:400e:c05::236; Original-Received: by mail-pg0-x236.google.com with SMTP id u5so19297428pgn.0 for ; Fri, 11 Aug 2017 12:47:22 -0700 (PDT) X-Received: by 10.84.129.131 with SMTP id b3mr19591403plb.415.1502480841638; Fri, 11 Aug 2017 12:47:21 -0700 (PDT) Original-Sender: nliber@gmail.com Original-Received: by 10.100.133.80 with HTTP; Fri, 11 Aug 2017 12:46:40 -0700 (PDT) In-Reply-To: <6240d6af-a518-4788-a56f-b7d0c8976dc4@isocpp.org> X-Original-Sender: nevin@eviloverlord.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=Lw7ZxGGA; spf=pass (google.com: domain of nliber@gmail.com designates 2607:f8b0:400e:c05::236 as permitted sender) smtp.mailfrom=nliber@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:33842 Archived-At: --94eb2c11972ad90aec05567f94b4 Content-Type: text/plain; charset="UTF-8" On Fri, Aug 11, 2017 at 12:01 PM, Nicol Bolas wrote: > `zstring_view` is conceptually a `string_view`. This means that it is a > pointer+size, so `size()` is always O(1). But this also means that if you > try to put a literal in a `zstring_view`, it will have to invoke > `char_traits::length` to get the length. This is good if you're actually > going to use begin/end iterator pairs. But it's painful if you're just > doing one-time forward iteration. > Is it really that painful in practice? I would expect a compiler to optimize the length call away for a zstring_view taking a C-string literal. Non-literals where you don't know the size are likely more of a problem, in that you might be turning a one-pass algorithm into a two-pass algorithm. -- Nevin ":-)" Liber +1-847-691-1404 -- 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/CAGg_6%2BMXUEs0Z3mCvEKWXdUQMVsZWxxM1qQpmtXtVJp6P_7K8w%40mail.gmail.com. --94eb2c11972ad90aec05567f94b4 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
On Fri, Aug 11, 2017 at 12:01 PM, Nicol Bolas <jmckesso= n@gmail.com> wrote:
`zstr= ing_view` is conceptually a `string_view`. This means that it is a pointer+= size, so `size()` is always O(1). But this also means that if you try to pu= t a literal in a `zstring_view`, it will have to invoke `char_traits::lengt= h` to get the length. This is good if you're actually going to use begi= n/end iterator pairs. But it's painful if you're just doing one-tim= e forward iteration.

Is it = really that painful in practice?=C2=A0 I would expect a compiler to optimiz= e the length call away for a zstring_view<char> taking a C-string lit= eral.

Non-literals where you don't know the si= ze are likely more of a problem, in that you might be turning a one-pass al= gorithm into a two-pass algorithm.
--
=C2=A0Nevin ":-)" Liber=C2=A0 <mailto:nevin@eviloverlord.com> =C2=A0+1-847-691-1404

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