220 33031 <8c168cd3-6dc2-97ab-848d-7eab8321e114@rrsd.com> article Path: news.gmane.org!.POSTED!not-for-mail From: Robert Ramey Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: safe integrals comparison Date: Thu, 29 Jun 2017 12:10:53 -0700 Lines: 42 Approved: news@gmane.org Message-ID: <8c168cd3-6dc2-97ab-848d-7eab8321e114@rrsd.com> References: <66f9bab2-7220-4bf1-afb7-77c5efa1bac3@isocpp.org> <4473c388-1bc0-24b3-b1f2-fc8bfc834df3@rrsd.com> <23282d1f-aaaa-45a1-a1fe-2056addfe835@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8"; format=flowed X-Trace: blaine.gmane.org 1498763458 21535 195.159.176.226 (29 Jun 2017 19:10:58 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 29 Jun 2017 19:10:58 +0000 (UTC) User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDG73K7L6AIRBQNB2XFAKGQEJLR6H6I@isocpp.org Thu Jun 29 21:10:54 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yb0-f197.google.com ([209.85.213.197]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dQeq6-0005Ot-5z for gclcip-std-proposals@m.gmane.org; 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[23.83.214.27]) by mx.google.com with ESMTPS id k16si4585293pli.350.2017.06.29.12.10.57 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 29 Jun 2017 12:10:57 -0700 (PDT) Received-SPF: pass (google.com: domain of ramey@rrsd.com designates 23.83.214.27 as permitted sender) client-ip=23.83.214.27; X-Sender-Id: wwwh2|x-authuser|ramey@rrsd.com Original-Received: from relay.mailchannels.net (localhost [127.0.0.1]) by relay.mailchannels.net (Postfix) with ESMTP id 759D43689BC for ; Thu, 29 Jun 2017 19:10:56 +0000 (UTC) Original-Received: from clippers.accountservergroup.com (unknown [100.96.129.109]) (Authenticated sender: wwwh2) by relay.mailchannels.net (Postfix) with ESMTPA id DEFB6368AA2 for ; Thu, 29 Jun 2017 19:10:55 +0000 (UTC) X-Sender-Id: wwwh2|x-authuser|ramey@rrsd.com Original-Received: from clippers.accountservergroup.com ([UNAVAILABLE]. [172.20.55.158]) (using TLSv1 with cipher DHE-RSA-AES256-SHA) by 0.0.0.0:2500 (trex/5.9.7); Thu, 29 Jun 2017 19:10:56 +0000 X-MC-Relay: Neutral X-MailChannels-SenderId: wwwh2|x-authuser|ramey@rrsd.com X-MailChannels-Auth-Id: wwwh2 X-Abaft-Left: 391b28d67b4d69c3_1498763456091_3388971698 X-MC-Loop-Signature: 1498763456091:1434664144 X-MC-Ingress-Time: 1498763456090 Original-Received: from ip68-6-126-194.sb.sd.cox.net ([68.6.126.194]:53424 helo=Roberts-Mac-mini.local) by clippers.accountservergroup.com with esmtpsa (TLSv1:DHE-RSA-AES128-SHA:128) (Exim 4.87) (envelope-from ) id 1dQeq7-0003Ed-41 for std-proposals@isocpp.org; Thu, 29 Jun 2017 12:10:55 -0700 Original-Newsgroups: gmane.comp.lang.c++.isocpp.proposals In-Reply-To: <23282d1f-aaaa-45a1-a1fe-2056addfe835@isocpp.org> Content-Language: en-US X-AuthUser: ramey@rrsd.com X-Original-Sender: ramey@rrsd.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of ramey@rrsd.com designates 23.83.214.27 as permitted sender) smtp.mailfrom=ramey@rrsd.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:33031 Archived-At: On 6/29/17 10:00 AM, federico.kircheis@gmail.com wrote: > Hi, > > I was just reading your implementation a couple of days ago, it's pretty > complicated with all those templated types ;-) > > (To be honest I found out of your library in March, when I listened to > the podcast episode, but then forgot to give a look to your implementation) > > I noticed you were not comparing the precision of the types like I did, > I guess I missed that I could use "make_unsigned". > I think the only difference is that I'm converting both types to the one > with the biggest range, and accounting that it may be the signed one. I > guess it may use less stack space, but I also think that it will never > make some difference. > > I guess your implementation for comparing integral types and mine are > completely interchangeable. > This is unnecessary. C/C++ type promotion rules do exactly this so it's redundant to do this in your code. The only problem is that C++ promotion rules sometime change signed to unsigned and change the value. The attached code keeps this from happening which is why it works. Note that my code guarantees zero runtime overhead in space or time. In fact it could even make one's program faster as in the case: unsigned int x; signed int y = -1 y < x // can be eliminated as it will always be true. Robert Ramey -- 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/8c168cd3-6dc2-97ab-848d-7eab8321e114%40rrsd.com. .