220 17949 article Path: news.gmane.org!not-for-mail From: "'Jeffrey Yasskin' via ISO C++ Standard - Future Proposals" Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Parsing Numbers Date: Mon, 18 May 2015 13:12:00 -0700 Lines: 61 Approved: news@gmane.org Message-ID: References: Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-Trace: ger.gmane.org 1431979945 18799 80.91.229.3 (18 May 2015 20:12:25 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 18 May 2015 20:12:25 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDDM34EO6QDRBJMP5GVAKGQEDMM7III@isocpp.org Mon May 18 22:12:25 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pd0-f200.google.com ([209.85.192.200]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1YuROh-0008C0-Lf for gclcip-std-proposals@m.gmane.org; Mon, 18 May 2015 22:12:23 +0200 Original-Received: by pdlj11 with SMTP id j11sf407334817pdl.0 for ; Mon, 18 May 2015 13:12:22 -0700 (PDT) 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:content-type:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:list-post:list-help:list-archive:list-subscribe :list-unsubscribe; bh=eD2ASBP8p+Y3mN/vEiD3pUqKv4JOr0AvxNbmvCZvSQE=; b=EkXhxVA312flK02V7c1lVGbZPKNoJbOicocx0cbEST9DHHVCAQdmMBPVbcM5Y1Yqu7 0p/aJ3SQHVNMxj2YH0mqX4a/2cL3fUrsGVsvyqL68XMfE6TVhltvlZrIh22MI+ZVmQ5E Subog/QKcDM+o0W6t0S3E8Yeu7ns63umwGxFu1ZB5AdMf2v4dWeYb+SrxwoEAhLOteQh FHVfoKpvdsBaCJ1PraKiNU67mimcKbzNajJ/jNRCtJbKvdXtoPmjTWZ446Ur1WQOUYtR rQTwExyAe+umFq0CF8sEwlmzME1pqOiOYLsUHqLQOEgwv5ghxEbPdgF09Sv6cBewfBR4 VioA== X-Gm-Message-State: ALoCoQlt2NIj7MASe+9Au1A6IQWqyCslq7EdqAQk97mRlNYLbA9EWEGdgW6WHm/kgUYfUbu+fSIo X-Received: by 10.66.121.164 with SMTP id ll4mr34903398pab.19.1431979942399; Mon, 18 May 2015 13:12:22 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.51.17.44 with SMTP id gb12ls761021igd.34.gmail; Mon, 18 May 2015 13:12:21 -0700 (PDT) X-Received: by 10.50.138.74 with SMTP id qo10mr16858979igb.39.1431979941671; Mon, 18 May 2015 13:12:21 -0700 (PDT) Original-Received: from mail-ie0-x236.google.com (mail-ie0-x236.google.com. [2607:f8b0:4001:c03::236]) by mx.google.com with ESMTPS id l1si9771944ict.78.2015.05.18.13.12.21 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 18 May 2015 13:12:21 -0700 (PDT) Received-SPF: pass (google.com: domain of jyasskin@google.com designates 2607:f8b0:4001:c03::236 as permitted sender) client-ip=2607:f8b0:4001:c03::236; Original-Received: by iesa3 with SMTP id a3so92851985ies.2 for ; Mon, 18 May 2015 13:12:21 -0700 (PDT) X-Received: by 10.50.73.169 with SMTP id m9mr16749527igv.37.1431979941520; Mon, 18 May 2015 13:12:21 -0700 (PDT) Original-Received: by 10.64.73.2 with HTTP; Mon, 18 May 2015 13:12:00 -0700 (PDT) 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:f8b0:4001:c03::236 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: , X-Original-From: Jeffrey Yasskin Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:17949 Archived-At: On Mon, May 18, 2015 at 1:11 PM, Jeffrey Yasskin wrote: > Woot! > > On Mon, May 18, 2015 at 11:34 AM, Olaf van der Spek > wrote: >> Let's get the party started. >> >> What have we got? >> >> We've got functions like strtol and stoi which take a const char* or >> std::string and return a number. >> >> long strtol(const char*, char **str_end, int base); >> int stoi(const std::string&, std::size_t* pos = 0, int base = 10); >> >> What do we want? >> >> Input should not be required to be null terminated, so string_view seems >> like a suitable input type. >> Error detection should be simpler, but not everyone is a fan of exceptions. > > Also, errors in parsing aren't generally exceptional. > >> And IMO skipping spaces should not be part of the parse function. > > +1. We should have a way to skip a string_view past spaces, but I > agree that normal parsing should probably insist that the number > appear at the start of the string. > >> There's also the question of what to do when not the entire input can be >> parsed. Return an error or not. > > I believe "not", so that these functions can be used in parsing larger formats. > >> So, what about this one? >> >> optional parse(string_view, std::size_t* pos = 0, int base = 10); >> >> An alternative could be: >> >> error_code parse(T&, string_view, std::size_t* pos = 0, int base = 10); > > I assume *pos gets the last position that was part of the parsed number? Er, the position one after that. > In the paper that proposes this, it'd be good to see examples of > parsing code using each of the possible interfaces. That'll help > produce a more informed decision than just looking at the interfaces > abstractly. > > Jeffrey -- --- 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/. .