220 35320 article Path: news.gmane.org!.POSTED!not-for-mail From: Brittany Friedman Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Other boolean type Date: Fri, 10 Nov 2017 14:16:20 -0600 Lines: 128 Approved: news@gmane.org Message-ID: References: <3ab3afca-0676-4c57-9d76-a0c934f3d2bd@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="001a114062ec1770ad055da69863" X-Trace: blaine.gmane.org 1510344990 26267 195.159.176.226 (10 Nov 2017 20:16:30 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 10 Nov 2017 20:16:30 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCHLPXGUXMJBBFMSTDIAKGQENKE2K4Y@isocpp.org Fri Nov 10 21:16:21 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-qk0-f200.google.com ([209.85.220.200]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1eDFiu-0006Fh-Rq for gclcip-std-proposals@m.gmane.org; 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[209.85.220.65]) by mx.google.com with SMTPS id q44sor6632755qtg.38.2017.11.10.12.16.21 for (Google Transport Security); Fri, 10 Nov 2017 12:16:21 -0800 (PST) Received-SPF: pass (google.com: domain of fourthgeek@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; X-Received: by 10.200.37.89 with SMTP id 25mr2653712qtn.268.1510344981172; Fri, 10 Nov 2017 12:16:21 -0800 (PST) Original-Received: by 10.140.20.163 with HTTP; Fri, 10 Nov 2017 12:16:20 -0800 (PST) In-Reply-To: X-Original-Sender: fourthgeek@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=Bg0msHmJ; spf=pass (google.com: domain of fourthgeek@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=fourthgeek@gmail.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=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:35320 Archived-At: --001a114062ec1770ad055da69863 Content-Type: text/plain; charset="UTF-8" I have occasionally had use for Lukazsiewicz logic ( yes, no, maybe ) in code from time to time, especially dealing with multiple selection checkboxes in UI code, or as a more useful standin for optional/expected bools. (yes && maybe) == maybe (maybe && no) == no (maybe == maybe) == true There are alternative interpretations of "tribool", like Kleene algebra (yes, no, undefined). In that logic, (undefined == undefined) == undefined This makes it incompatible with Lukazsiewicz. As I understand, boost tribool uses Kleene algebra. Personally I have found Lukazsiewicz easier to understand and more useful. The point of this post was to point out that any proposition of creating a tribool needs to have a very clear idea of what this third state actually means. https://en.wikipedia.org/wiki/Three-valued_logic On Fri, Nov 10, 2017 at 8:01 AM, Robert Ramey wrote: > On 11/9/17 5:57 PM, g34rst@gmail.com wrote: > >> A type like a boolean but with three states false true and undefined, the >> default value would be undefined, in cases where the type is not initialy >> true or not initialy false. >> >> > boost tribool > > 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/is > ocpp.org/d/msgid/std-proposals/ou4bfs%24r3c%241%40blaine.gmane.org. > -- 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/CADbh%2BeQdLJ3uuA%2BMXF8zY33dMtrMHVW%3D3r25fyCwD4p3wkP8%3DQ%40mail.gmail.com. --001a114062ec1770ad055da69863 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
I have occasionally had use for Lukazsiewicz logic ( yes, = no, maybe ) in code from time to time, especially dealing with multiple sel= ection checkboxes in UI code, or as a more useful standin for optional/expe= cted bools.

(yes && maybe) =3D=3D maybe
(maybe && no) =3D=3D no
(maybe =3D=3D maybe) =3D=3D tru= e

There are alternative interpretations of "t= ribool", like Kleene algebra (yes, no, undefined). In that logic,
(undefined =3D=3D undefined) =3D=3D undefined

This makes it incompatible with Lukazsiewicz.

As= I understand, boost tribool uses Kleene algebra. Personally I have found L= ukazsiewicz easier to understand and more useful.

= The point of this post was to point out that any proposition of creating a = tribool needs to have a very clear idea of what this third state actually m= eans.


On Fri,= Nov 10, 2017 at 8:01 AM, Robert Ramey <ramey@rrsd.com> wrote:<= br>
On 11/9/17 5:57 PM, g34rst@gmail.com wrot= e:
A type like a boolean but with three states false true and undefined, the d= efault value would be undefined, in cases where the type is not initialy tr= ue or not initialy false.


 boost tribool

Robert Ramey

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