220 12895 article Path: news.gmane.org!not-for-mail From: Richard Smith Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: unevaluated this Date: Mon, 15 Sep 2014 14:00:08 -0700 Lines: 218 Approved: news@gmane.org Message-ID: References: <009e6218-1e2b-402d-ab1a-e8ebf29f8f77@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=001a11339e8883088e050320eb36 X-Trace: ger.gmane.org 1410814820 3327 80.91.229.3 (15 Sep 2014 21:00:20 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 15 Sep 2014 21:00:20 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDVNBJG4YAIBBWNG3WQAKGQEQWOPZZY@isocpp.org Mon Sep 15 23:00:15 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-oa0-f72.google.com ([209.85.219.72]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1XTdNb-00075z-1n for gclcip-std-proposals@m.gmane.org; Mon, 15 Sep 2014 23:00:11 +0200 Original-Received: by mail-oa0-f72.google.com with SMTP id g18sf23039840oah.11 for ; Mon, 15 Sep 2014 14:00:10 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:sender:in-reply-to:references:date :message-id:subject:from:to: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=0EynqAJBLedFxoVNXpQs8p/5nVCWNb2qNFk0Zxn8y5I=; b=HKpbVT/KPVHeR7Mz7lbaP30xRmzcviublb2xFNQbiAyl5SO5bC3xRbvPMlM30WTKxR CB4k0jkSgqLYz01REhXW00wnpFTLDMv2JVQQaO1XHMBY0oax1Gqns9/dikNuKx3NA07f U1aYJaGL0vkggfDW/MVynlOFq2ymsZ+TlNF0GttbbUelrd0xU2jbF0OksGn3iDMSwzTN OVEbMZj882IAOWoryX3tZZNMHmUq95+Rhg/uKXsIw3HXhKp29lwMVZKMErEVlMwvTUI0 Pv5n7OJDOROGE20JXkXLfjuM4pdAlR5QzNryt/EIEDJruG5YLHkqIVM2qBATy/5oxA4w RpZQ== X-Gm-Message-State: ALoCoQnzRoAkCOE08/BKvIducNnb0DG+Q3/o0EInbswh56FPgv0hxb+NqZ23pk/NXjzlwUjuJ52r X-Received: by 10.42.188.210 with SMTP id db18mr17772381icb.9.1410814809993; Mon, 15 Sep 2014 14:00:09 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.140.21.146 with SMTP id 18ls1668602qgl.81.gmail; Mon, 15 Sep 2014 14:00:09 -0700 (PDT) X-Received: by 10.220.69.210 with SMTP id a18mr3528382vcj.67.1410814808967; Mon, 15 Sep 2014 14:00:08 -0700 (PDT) Original-Received: from mail-vc0-x22d.google.com (mail-vc0-x22d.google.com [2607:f8b0:400c:c03::22d]) by mx.google.com with ESMTPS id ci16si6712403vdb.93.2014.09.15.14.00.08 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 15 Sep 2014 14:00:08 -0700 (PDT) Received-SPF: pass (google.com: domain of metafoo@gmail.com designates 2607:f8b0:400c:c03::22d as permitted sender) client-ip=2607:f8b0:400c:c03::22d; Original-Received: by mail-vc0-f173.google.com with SMTP id le20so4039173vcb.32 for ; Mon, 15 Sep 2014 14:00:08 -0700 (PDT) X-Received: by 10.221.44.69 with SMTP id uf5mr25660124vcb.4.1410814808620; Mon, 15 Sep 2014 14:00:08 -0700 (PDT) Original-Sender: metafoo@gmail.com Original-Received: by 10.220.76.200 with HTTP; Mon, 15 Sep 2014 14:00:08 -0700 (PDT) In-Reply-To: X-Original-Sender: richard@metafoo.co.uk X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of metafoo@gmail.com designates 2607:f8b0:400c:c03::22d as permitted sender) smtp.mail=metafoo@gmail.com; dkim=pass header.i=@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:12895 Archived-At: --001a11339e8883088e050320eb36 Content-Type: text/plain; charset=UTF-8 On Mon, Sep 15, 2014 at 12:39 PM, Sean Middleditch wrote: > Yeah, that was one of the open questions. Would using the this_t<> > alternative (delaying the instantiation until the appropriate context) > work? > > The this_t idea is just to offer a convenience shorthand. I don't > think it's necessary, and the my_type you present is certainly > acceptable; this isn't something users are expected to use directly > too often. > The this_t thing doesn't work: 'this' will be interpreted in the context in which it appears, and in the definition of 'this_t' it appears outside a class, so is ill-formed. > Thanks! > > On Mon, Sep 15, 2014 at 11:32 AM, Myriachan wrote: > > On Monday, September 15, 2014 9:17:17 AM UTC-7, Sean Middleditch wrote: > >> > >> Another proposal carrying on from work I did earlier. This is a > >> continuation of the decltype(class) feature I suggested some time back > but > >> with Ville's suggestion taken to heart. It's now a proposal for allowing > >> `this` in unevaluated contexts (decltype, sizeof, etc.) anywhere in a > class > >> definition body or base specifier list as well as a convenient helper > >> `std::this_t`. > >> > >> > >> > http://htmlpreview.github.io/?https://github.com/seanmiddleditch/CPlusPlus/blob/master/unevaluated-this.html > >> > >> Thoughts/comments/critiques would be appreciated. Thanks! > > > > > > I don't see how std::this_t could be implemented, because there's no way > it > > could know in which context it's being used. Other than the amount of > > typing, this would work fine if this is allowed throughout class scope in > > all unevaluated contexts: > > > > using my_type = > std::remove_cv_t>; > > > > Melissa > > > > -- > > > > --- > > You received this message because you are subscribed to a topic in the > > Google Groups "ISO C++ Standard - Future Proposals" group. > > To unsubscribe from this topic, visit > > > https://groups.google.com/a/isocpp.org/d/topic/std-proposals/pienLjyOVJk/unsubscribe > . > > To unsubscribe from this group and all its topics, send an email to > > std-proposals+unsubscribe@isocpp.org. > > To post to this group, send email to std-proposals@isocpp.org. > > Visit this group at > > http://groups.google.com/a/isocpp.org/group/std-proposals/. > > > > -- > Sean Middleditch > http://seanmiddleditch.com > > -- > > --- > 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. > Visit this group at > http://groups.google.com/a/isocpp.org/group/std-proposals/. > -- --- 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. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposals/. --001a11339e8883088e050320eb36 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
On M= on, Sep 15, 2014 at 12:39 PM, Sean Middleditch <sean@middleditch.us&= gt; wrote:
Yeah, that was one of t= he open questions. Would using the this_t<>
alternative (delaying the instantiation until the appropriate context)
work?

The this_t idea is just to offer a convenience shorthand. I don't
think it's necessary, and the my_type you present is certainly
acceptable; this isn't something users are expected to use directly
too often.

The this_t thing doesn't= work: 'this' will be interpreted in the context in which it appear= s, and in the definition of 'this_t' it appears outside a class, so= is ill-formed.
=C2=A0
Thanks!

On Mon, Sep 15, 2014 at 11:32 AM, Myriachan <myriachan@gmail.com> wrote:
> On Monday, September 15, 2014 9:17:17 AM UTC-7, Sean Middleditch wrote= :
>>
>> Another proposal carrying on from work I did earlier. This is a >> continuation of the decltype(class) feature I suggested some time = back but
>> with Ville's suggestion taken to heart. It's now a proposa= l for allowing
>> `this` in unevaluated contexts (decltype, sizeof, etc.) anywhere i= n a class
>> definition body or base specifier list as well as a convenient hel= per
>> `std::this_t`.
>>
>>
>> ht= tp://htmlpreview.github.io/?https://github.com/seanmiddleditch/CPlusPlus/bl= ob/master/unevaluated-this.html
>>
>> Thoughts/comments/critiques would be appreciated. Thanks!
>
>
> I don't see how std::this_t could be implemented, because there= 9;s no way it
> could know in which context it's being used.=C2=A0 Other than the = amount of
> typing, this would work fine if this is allowed throughout class scope= in
> all unevaluated contexts:
>
> using my_type =3D std::remove_cv_t<std::remove_reference_t<declt= ype(*this)>>;
>
> Melissa
>
> --
>
> ---
> You received this message because you are subscribed to a topic= in the
> Google Groups "ISO C++ Standard - Future Proposa= ls" group.
> To unsubscribe from this topic, visit
> https://groups.google.com/a/is= ocpp.org/d/topic/std-proposals/pienLjyOVJk/unsubscribe.
> To unsubscribe from this group and all its topics, send an email to > std-proposals+unsubscribe@isocpp.org.
> To post to this group, send email to std-proposals@isocpp.org.
> Visit this group at
> http://groups.google.com/a/isocpp.org/group/std-proposal= s/.



--
Sean Middleditch
http://seanmiddled= itch.com

--

---
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--

---
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