220 13414 <6449799.vbEiQqPBsP@tjmaciei-mobl4> article Path: news.gmane.org!not-for-mail From: Thiago Macieira Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: atof(string_view) and others Date: Tue, 30 Sep 2014 19:40:42 -0700 Lines: 73 Approved: news@gmane.org Message-ID: <6449799.vbEiQqPBsP@tjmaciei-mobl4> References: <2118839.fukHYmiT6S@tjmaciei-mobl4> <77247918-fbe5-418d-ab30-8b4b852dace9@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 1412131254 27337 80.91.229.3 (1 Oct 2014 02:40:54 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 1 Oct 2014 02:40:54 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCB4TK757YBRBL6TVWQQKGQEJCENT2I@isocpp.org Wed Oct 01 04:40:49 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-la0-f71.google.com ([209.85.215.71]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1XZ9qT-0001op-D6 for gclcip-std-proposals@m.gmane.org; Wed, 01 Oct 2014 04:40:49 +0200 Original-Received: by mail-la0-f71.google.com with SMTP id gi9sf87553lab.2 for ; Tue, 30 Sep 2014 19:40:49 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:subject:date:message-id:user-agent :in-reply-to:references:mime-version: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=fAPvAttxKSg95fUxHyJCj57ObiiycG2heQzT4z4NC4k=; b=d+ex5Xp9RXjUyJcRH6u2MnffHOiR7JGQDo16PZhyVVY7tofqFGDbVPJnLT8Uj/ZijV YMGKkqDM8Hli4ySKFRMj2YCfOenRq475tga5aXm7/rYmqG/BBNNiRP3QOhWpSOpQwbw7 NqppTLq2Cs4IFZqMQAbcD0o4HrpoeuB+cFbAxPxUQW2v7txRdIrn/Ey1Vrq4dWswVbUo 6/t85H75uJ0JDXddyHRlM4cn+4ot13aBhx6wSI+l4ZunQvchFgURzJqDqkfLPdG4p0MO QgoCoYnJ/ofWqhtbRf0scPXLuZdwjlQ9V0i5jQP185qAOs+nUOMKVgXkdBIeRsA9z4jx F3dQ== X-Gm-Message-State: ALoCoQmkoRhVVgDZuzfWAzD2uyMDLm/rFsOtOrhJbgNzdQ/v6Ermu5qkV9IWRzP2zshydyazomC5 X-Received: by 10.112.168.225 with SMTP id zz1mr1074042lbb.8.1412131249193; Tue, 30 Sep 2014 19:40:49 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.152.5.38 with SMTP id p6ls108511lap.72.gmail; Tue, 30 Sep 2014 19:40:46 -0700 (PDT) X-Received: by 10.152.1.74 with SMTP id 10mr41243701lak.43.1412131246864; Tue, 30 Sep 2014 19:40:46 -0700 (PDT) Original-Received: from gondolin.macieira.info (gondolin.macieira.info. [78.47.120.188]) by mx.google.com with ESMTP id lk1si25281976lac.4.2014.09.30.19.40.46 for ; Tue, 30 Sep 2014 19:40:46 -0700 (PDT) Received-SPF: pass (google.com: domain of thiago@macieira.org designates 78.47.120.188 as permitted sender) client-ip=78.47.120.188; Original-Received: from tjmaciei-mobl4.localnet (unknown [IPv6:2601:7:1c80:58c:30e7:a180:29c0:1e9d]) by gondolin.macieira.info (Postfix) with ESMTPSA id 130BC11BA60 for ; Tue, 30 Sep 2014 19:40:45 -0700 (PDT) User-Agent: KMail/4.14 (Linux/3.11.10-21-desktop; KDE/4.14.0; x86_64; ; ) In-Reply-To: <77247918-fbe5-418d-ab30-8b4b852dace9@isocpp.org> X-Original-Sender: thiago@macieira.org X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of thiago@macieira.org designates 78.47.120.188 as permitted sender) smtp.mail=thiago@macieira.org 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:13414 Archived-At: On Tuesday 30 September 2014 19:13:40 Matthew Fioravante wrote: > 1. You lose the ability to check specific error conditions like ERANGE. > I'm not sure how useful this is as I've never done an ERANGE check on a > number parse but that functionality is available with the legacy > functions. I don't see how that relates to the optional. In fact, I don't see how you came to this conclusion. If the parsing failed, the function will return a disengaged optional and set errno to ERANGE or EINVAL. If it worked, it will return an engaged optional and errno is unspecified. That's much better than strtoul, which returns zero when it fails and that's undistinguishable from a successful parsing of a number zero. > 2. If you want to enable a throwing interface by just calling > optional::value() and letting it throw on error, you'll be throwing a > std::bad_optional_access. It would be better to throw an exception class > which is more specifically related to parsing numbers and has information > on what went wrong. I again don't understand why that is a problem. What's stopping you from throwing an exception if the returned optional is disengaged? > Also I think its better to use a string_view& for the tail instead of a > char**. The tail string itself is not null terminated so using a character > pointer with which we usually associate null termination is a big > misleading. Also converting the char** endptr back into a string_view is > clumsy and error prone as it will call strlen() on the non-null terminated > buffer unless the programmer carefully computes and specifies the new > length. Yeah, that makes sense. I was pondering that when I wrote the suggestion, but didn't go through with it. > I'd also like to try to make the integer conversions constexpr so setting > errno is out. Forget it. Non-inline functions can't be constexpr and those functions shouldn't be inline. At best, they could be an inline wrapper to the real parser, such as: template optional to_integral(string_view str, int base = 10, string_view *tail = nullptr) { typedef typename conditional::value, unsigned long long, long long>::type U; U min = numeric_limits::min(); U max = numeric_limits::max(); optional result = to_integral_helper(str, base, tail, min, max); return result ? optional(result.value()) : optional(); } This will require two only out-of-line functions, one for long long (for signed conversions) and one for unsigned long long (for unsigned ones). -- Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org Software Architect - Intel Open Source Technology Center PGP/GPG: 0x6EF45358; fingerprint: E067 918B B660 DBD1 105C 966C 33F5 F005 6EF4 5358 -- --- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. 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