220 9025 article Path: news.gmane.org!not-for-mail From: Jeffrey Yasskin Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: String to T conversions - getting it right this time Date: Mon, 3 Feb 2014 09:46:27 -0800 Lines: 85 Approved: news@gmane.org Message-ID: References: <097fb6c8-56f9-433e-a2f0-8c0f69609bf0@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 X-Trace: ger.gmane.org 1391449605 1538 80.91.229.3 (3 Feb 2014 17:46:45 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 3 Feb 2014 17:46:45 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDDM34EO6QDRBCFMX6LQKGQEQ5FJQAI@isocpp.org Mon Feb 03 18:46:53 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-oa0-f70.google.com ([209.85.219.70]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1WANbe-0006WE-GX for gclcip-std-proposals@m.gmane.org; Mon, 03 Feb 2014 18:46:50 +0100 Original-Received: by mail-oa0-f70.google.com with SMTP id m1sf31975165oag.9 for ; Mon, 03 Feb 2014 09:46:49 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; 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=vffJ1JBiUy6o2QOChQHNroBfuPmTvgfJZiGRzvxwp9c=; b=LXBZgqtG4GWJQ7TeV4BAwYhR/ormVGMygOtmFI+6Q1jSIHPMGrulPv9gDkwaZ0oTjB V9znmyojH6OYnbgAzAYbLaj8iN3xHXe4vwDxQJ52hxJsF+Tmx2nPO3CoUBu2LQ0kihds S/lEDlDI4ZzJjUxPUTHVUcHXZY/1Tz5O5aPewmPtuuqzfH+Z6ULpefE9pT9orMhgqWi0 dfevEpMV69cnrYRe6ogGpXEoZCyTdMMvTU/WmF8K6+zhb3u5RFL9oy10Tr5QQ2bBFUQ5 T4EQU6BykZd8vUcFcKjgXwEhnqnyly+tJU5RHgbHW+RW/0Zb7oTnRlqax5c2f881JRgg WS3Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state: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=vffJ1JBiUy6o2QOChQHNroBfuPmTvgfJZiGRzvxwp9c=; b=H35iz7tdJ60wCeD7NyW/0zwZ5ofapMfg3o3Act7UzheXQwuN2oXoZUxgRRRUE+Cc6x ggWD4NH1BaTlgttbefcuPveZOvxGHEW+88bMKBOnYhoWNw1qEnzZGmRNSPrqJ0OebdBQ orVJMoHrark9vNLfZ2lU2XR5GNnpzPW5e2oo3UmUJIxefwCNLF16EsTvMwXIj2RrGEw/ y3t8E3D73XBnaMRwQ/+uzmfYgqeH4BVVyO4mw9xgx3ENNorGGyw0pqw9URZM/S1kbbEn tJvlRIs6dBrhKgHxIYmhnBPnH5GCDYMaMzt2l21wokRX1YZY06VzgIVrL7RI2tklCLJk PfoA== X-Gm-Message-State: ALoCoQnYbqGxxnIl0QSCqdlEfzV2hz0GaWC58FefrPUhTqo67pWwVA72t5uOl9+9tOcWgBP54MaX X-Received: by 10.42.235.132 with SMTP id kg4mr2209304icb.32.1391449609420; Mon, 03 Feb 2014 09:46:49 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.140.26.40 with SMTP id 37ls1919615qgu.46.gmail; Mon, 03 Feb 2014 09:46:48 -0800 (PST) X-Received: by 10.140.31.247 with SMTP id f110mr54388298qgf.58.1391449608681; Mon, 03 Feb 2014 09:46:48 -0800 (PST) Original-Received: from mail-qc0-x233.google.com (mail-qc0-x233.google.com [2607:f8b0:400d:c01::233]) by mx.google.com with ESMTPS id a3si15296727qam.90.2014.02.03.09.46.48 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 03 Feb 2014 09:46:48 -0800 (PST) Received-SPF: pass (google.com: domain of jyasskin@google.com designates 2607:f8b0:400d:c01::233 as permitted sender) client-ip=2607:f8b0:400d:c01::233; Original-Received: by mail-qc0-f179.google.com with SMTP id e16so11521474qcx.38 for ; Mon, 03 Feb 2014 09:46:48 -0800 (PST) X-Received: by 10.224.120.199 with SMTP id e7mr58095795qar.47.1391449608343; Mon, 03 Feb 2014 09:46:48 -0800 (PST) Original-Received: by 10.229.227.8 with HTTP; Mon, 3 Feb 2014 09:46:27 -0800 (PST) In-Reply-To: X-Original-Sender: jyasskin@google.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of jyasskin@google.com designates 2607:f8b0:400d:c01::233 as permitted sender) smtp.mail=jyasskin@google.com; dkim=pass header.i=@google.com; dmarc=pass (p=REJECT dis=NONE) header.from=google.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:9025 Archived-At: On Mon, Feb 3, 2014 at 9:36 AM, Matthew Woehlke wrote: > On 2014-02-03 11:25, Olaf van der Spek wrote: >> >> On Mon, Feb 3, 2014 at 5:20 PM, Matthew Woehlke >> wrote: >>>> >>>> I'd prefer 07 to be parsed as 7. Most non-dev people probably expect >>>> this >>>> as well. >>>> Is octal still being used? >>> >>> >>> >>> You can do this by passing base = 10. '0' as a prefix only means base 8 >>> when >>> passing base = 0 (i.e. detect from prefix). >> >> >> What if I want dec and hex but no octal? ;) > > > That's a fair question :-). (But so is if we should throw out the 0 prefix > as indicating octal.) > > I suppose you could test if the string starts with '0x' and call with either > in,base=10 or in+2,base=16. Not saying that's ideal, though. (Even if I > suspect that performance-wise it would be similar to base=0.) > > >>>> What's the problem with strlen()? >>> >>> >>> It requires additional execution cycles that don't provide any real >>> benefit. >>> And yes, that *does* matter; there are definitely cases where string to >>> number conversion is a performance bottleneck, e.g. when reading large >>> files >>> of data in textual format. (I say this from actual real-world personal >>> experience.) >> >> >> Numbers in text files are not nul-terminated. > > > They are if I'm using a CSV or XML parsing library that yields > NUL-terminated char*. (And I seem to recall that such do exist, i.e. they > take a char* buffer and substitute NUL at the end of "values".) FWIW, your CSV or XML parsing library should be changed to return a string_view or equivalent. It has the size, and is throwing it out, forcing your number parser to do redundant checks for '\0', which slows you down. Yes, I know it will take time to propagate the new interface through system libraries. > "What's the problem with strlen()" is that is has potential performance > implications given char const* input data. I'm not convinced that trying to > determine if there is any reasonable instance where one has char const* data > in a situation that is performance sensitive qualifies as reason to > disregard that. > > -- > Matthew > > > -- > > --- 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/. -- --- 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. 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