220 32201 article Path: news.gmane.org!.POSTED!not-for-mail From: David Peterson Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Idea: New Language Feature for Safer, Easier Optional Access Date: Thu, 27 Apr 2017 09:54:51 -0700 (PDT) Lines: 65 Approved: news@gmane.org Message-ID: References: <921cd9f6-f26b-c674-6609-d924cf7d2758@wanadoo.fr> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_3791_325996676.1493312092026" X-Trace: blaine.gmane.org 1493312092 5981 195.159.176.226 (27 Apr 2017 16:54:52 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 27 Apr 2017 16:54:52 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBC2O5JM7VUCBBXGERDEAKGQEAJYDUAA@isocpp.org Thu Apr 27 18:54:49 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pf0-f200.google.com ([209.85.192.200]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1d3mgp-0001SB-U0 for gclcip-std-proposals@m.gmane.org; Thu, 27 Apr 2017 18:54:48 +0200 Original-Received: by mail-pf0-f200.google.com with SMTP id a188sf30619435pfa.3 for ; Thu, 27 Apr 2017 09:54:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=Aj95gjvsJugqIDm5XsfmYXIJGYsLA+T/zf6bynXw9Us=; b=1QfoCbZ5woL7Dg42ED6YIOtz8yjxLORZEv5FYcakUCqtO6EkM3GS5p25dDOocg4Pkp cOkwHzp4/riGz6URqK16xld3iZW7tAdPMbqYwgqnbB+VPKzVI22kmPKx+mhMtR4fo7U1 nZxIgF5OJov5T0Pa65L0zkS2MEPOIiKvJvFjXiJPH7M+islL2ktTKZuboz/im3qbUpK5 +LeD6FQC7eRodyg7OdsTs94DEDCOPPs2lWvfQDNZbfbj7vsIH07ubGxBKFO04U4rGGax 1Yo2uMQYeWuMztL/JNrTo5zOME92Jwn9ZdyVQPEQNFc+7OEGS8izfExf2S1Ms/DiprE3 qauA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:message-id:in-reply-to:references :subject:mime-version:x-original-sender:reply-to:precedence :mailing-list:list-id:x-spam-checked-in-group:list-post:list-help :list-archive:list-subscribe:list-unsubscribe; bh=Aj95gjvsJugqIDm5XsfmYXIJGYsLA+T/zf6bynXw9Us=; b=hVA98w7D1ftI0dDYmE5wnjAIYvAvL0yrowiWjQp22ZDiYU97ad4O0oqWQf0vWXs1Ra huwBmbpuyT7FLEwzpZkVQlTUjQiknsDTJnoufq1je/+cC/0VPgyXv6CbQMa18iMNsXGo fvLp5M57JMIQNPivWK+bIV038/vX2df0DPjmDxblIZP1mS9W2Q6M+iaJeY7SQ3WNNxna Igi4yJxirMYNLpAxB9gNLK+dK7vyGRA1wva77QCK7jEf3iIRY3BE5UE1p8mFTH3bJqSz f+/yn5Ip9/oGuVME7cX8bJp+MHWKqAgZRuqy1zIN7S8K3as6LNFcgYiaUoEVAVjcbv6F MBvg== X-Gm-Message-State: AN3rC/4RWh2eQoaLEJ8Zr/ciZrG7c/AVSwBg9FKe6A/1eaj0G1E8wxD4 tGE0sWeFaxHCew== X-Received: by 10.99.167.13 with SMTP id d13mr2998532pgf.82.1493312093481; Thu, 27 Apr 2017 09:54:53 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.37.235 with SMTP id q98ls3978258ota.49.gmail; Thu, 27 Apr 2017 09:54:52 -0700 (PDT) X-Received: by 10.157.8.17 with SMTP id 17mr143446oty.20.1493312092562; Thu, 27 Apr 2017 09:54:52 -0700 (PDT) In-Reply-To: <921cd9f6-f26b-c674-6609-d924cf7d2758@wanadoo.fr> X-Original-Sender: djpeterson83@hotmail.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:32201 Archived-At: ------=_Part_3791_325996676.1493312092026 Content-Type: multipart/alternative; boundary="----=_Part_3792_2099221978.1493312092026" ------=_Part_3792_2099221978.1493312092026 Content-Type: text/plain; charset=UTF-8 > > The language based variant proposal [1] (I hope will be part of C++20) > will allow to do pattern matching.I believe this will be more adapted and > will take in account std::expected as well. This looks similar to Rust's enumeration and pattern matching. In all honesty, I think I would prefer this pattern matching system to a built in optional. This seems extremely flexible and could be used for run-time validation as well (such as a variant which is either a SuccessObject or a FailureObject after a process completes). I hope that templating is included when (if?) the proposal is ratified as this would easily solve the issue with optionals in a very safe, easy to use way. -- 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/b2a4b389-936c-4e2a-845a-ddccca84262c%40isocpp.org. ------=_Part_3792_2099221978.1493312092026 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
= The language based variant proposal [1] (I hope will be part of C++20) will= allow to do pattern matching.I believe this will be more adapted and will = take in account std::expected as well.
=C2=A0
Th= is looks similar to Rust's enumeration and pattern matching. =C2=A0In a= ll honesty, I think I would prefer this pattern matching system to a built = in optional. =C2=A0This seems extremely flexible and could be used for run-= time validation as well (such as a variant which is either a SuccessObject = or a FailureObject after a process completes). =C2=A0I hope that templating= is included when (if?) the proposal is ratified as this would easily solve= the issue with optionals in a very safe, easy to use way.

--
You received this message because you are subscribed to the Google Groups &= quot;ISO C++ Standard - Future Proposals" group.
To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+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/b2a4b389-936c-4e2a-845a-ddccca84262c= %40isocpp.org.
------=_Part_3792_2099221978.1493312092026-- ------=_Part_3791_325996676.1493312092026-- .