220 33046 <2991b2b2-2f62-42e2-83d1-f42dae9c32c1@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Barry Revzin Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: std::optional - support for sentinel values Date: Fri, 30 Jun 2017 12:28:12 -0700 (PDT) Lines: 68 Approved: news@gmane.org Message-ID: <2991b2b2-2f62-42e2-83d1-f42dae9c32c1@isocpp.org> References: <6e23864f-827a-4bdb-89de-a60d8f5be993@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_593_15458201.1498850892787" X-Trace: blaine.gmane.org 1498850894 12740 195.159.176.226 (30 Jun 2017 19:28:14 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 30 Jun 2017 19:28:14 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCJJTG7CS4ARBTOM3LFAKGQEQA53P5Y@isocpp.org Fri Jun 30 21:28:10 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-vk0-f72.google.com ([209.85.213.72]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dR1aL-000326-Ud for gclcip-std-proposals@m.gmane.org; Fri, 30 Jun 2017 21:28:10 +0200 Original-Received: by mail-vk0-f72.google.com with SMTP id o190sf45187931vka.10 for ; Fri, 30 Jun 2017 12:28:15 -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 :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=1RCNR6uPHFmGt/WS1kI0FdWBgMEXl61Jok6M1XEZWGk=; b=LZbdultKS+3wZlfQJ9XAWNTdkQfXV21wGrZTCf/N2NMNc1guMQC3MPSaEYmEjmtyFF clJRI2D9Zd0eQ0eRYFyCITA7WiT2K8VImAIDtEk6/eCioK8vdmwMaLybbHlEwwbfK5P6 pyQx63zREkxh7bsqa4esW1NrDmNRXcpdvdETOFYFf6GILXT/hwWjX87eBbXhuofXrZTc y3ErUWdibfrX4SoF8ULX/lL4WkiKvlRxB+HpFwLg2DQWJ8CiAOaa1jdZmcjfW8wIcriz ujTR+at3JdxrEQReenZylmwr5BuYX6IJlzSXBQM6QA5wHBeeUDkvi43zfTEOAFRd3QgA 1nyw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=1RCNR6uPHFmGt/WS1kI0FdWBgMEXl61Jok6M1XEZWGk=; b=pzqjUZQCI149+U/BZjTjmdvPuBvocnZaabbYI+ClyYu1GgWGi9HwJdJcqVpwISplHi QOPQRGhZfRE1W3sCo3PEWlokRxzT9CPWV8CpINJMO8MLwS1YcPz78uY1KexdzCGbfv/Y Y2EGiJ0L1R5atGnpYc3i+uCC4TvON95ZOR+4mL5uTeSmTA8LFpSsxIIF+PnwBr/RgOkj Ntl9LmaDmtwtf/t78cFsbmR6gEWopNrX3m1pgNGOpaE0vIbcPczghLuUkZz7QyCQNd9q 2fmzq9o7m2M2aZk/qFg8ZLQvnbgIVufJdfqDg0oQ4uaMJFzPyTXLAH5XNd16/AuOVekR 6ZwA== 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=1RCNR6uPHFmGt/WS1kI0FdWBgMEXl61Jok6M1XEZWGk=; b=E+wMyQooDw9icibOtYglf3R7695rO4vgspL/f+iFA6oP+h96E9eCOxao9+pBe58hfw 9aeLtcUlIZOyTB8zqClZG31vnFlRgRnthyu//G9ra9ppDFPDMpZZpEgxlaMhCCSG9Yet B7UUFZCudJOkf95j3HTjLktJtAVZGFnGgA73zuqCBWQ66/84gzwjHoRevy3w8IhWvU1V JpsXU8qYTr9lAIGpT2SItTkiUPwwWkkQylVkzR7RdIEUDw2gJ3OxR2ppDD2ltoi1trF4 epM+Pb+fnPOxAWQ2gMODz7vOIh+p8gfwm3YdFfQUfT8OLt+Z4GXZHEG5lHjrLbiW63AH EmKA== X-Gm-Message-State: AKS2vOw/1gaNy7YsmBi281V+RCXe25wbQsoYFq2stVwHAVqTGL8bJGeM cJt3++rkLHxZI7zl X-Received: by 10.176.92.28 with SMTP id q28mr7284268uaf.12.1498850895066; Fri, 30 Jun 2017 12:28:15 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.36.94.142 with SMTP id h136ls3229901itb.0.gmail; Fri, 30 Jun 2017 12:28:13 -0700 (PDT) X-Received: by 10.36.46.202 with SMTP id i193mr653094ita.8.1498850893349; Fri, 30 Jun 2017 12:28:13 -0700 (PDT) In-Reply-To: X-Original-Sender: Barry.Revzin@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:33046 Archived-At: ------=_Part_593_15458201.1498850892787 Content-Type: multipart/alternative; boundary="----=_Part_594_530934191.1498850892787" ------=_Part_594_530934191.1498850892787 Content-Type: text/plain; charset="UTF-8" > > > This is optional>. > As for why optional is a terrible, horrible, no-good, very bad idea, > please see Matt Calabrese's talk > from C++Now. > > That's not at all the impression I got from that talk. One of the things he specifically mentions as a good idea is to support references for optional/variant, but internally wrap the references so that they behave as regular types (that is, like pointers. so operator= would rebind references, not assign through them). -- 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/2991b2b2-2f62-42e2-83d1-f42dae9c32c1%40isocpp.org. ------=_Part_594_530934191.1498850892787 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable

This is optional<reference_wrapper<T>><= wbr>.
As for why optional<T&> is a terrible, horrible, = no-good, very bad idea, please see Matt Calabrese's talk from C++Now.

That's not at all the im= pression I got from that talk. One of the things he specifically mentions a= s a good idea is to support references for optional/variant, but internally= wrap the references so that they behave as regular types (that is, like po= inters. so operator=3D would rebind references, not assign through them).

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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/2991b2b2-2f62-42e2-83d1-f42dae9c32c1= %40isocpp.org.
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