220 2741 article Path: news.gmane.org!not-for-mail From: =?UTF-8?Q?Andrzej_Krzemie=C5=84ski?= Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: optional references -- take 2 Date: Tue, 5 Feb 2013 12:02:42 -0800 (PST) Lines: 98 Approved: news@gmane.org Message-ID: References: <8d57e9e9-e4cc-441c-abeb-e6526531fad5@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_1772_14843462.1360094562219" X-Trace: ger.gmane.org 1360094563 4921 80.91.229.3 (5 Feb 2013 20:02:43 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Tue, 5 Feb 2013 20:02:43 +0000 (UTC) Cc: Sean Parent To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDT2DGOJ34DBBY6KYWEAKGQE46XBNVI@isocpp.org Tue Feb 05 21:03:03 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-qe0-f70.google.com ([209.85.128.70]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1U2ojO-0001h0-D4 for gclcip-std-proposals@m.gmane.org; Tue, 05 Feb 2013 21:03:02 +0100 Original-Received: by mail-qe0-f70.google.com with SMTP id 1sf850063qec.1 for ; Tue, 05 Feb 2013 12:02:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=x-received:x-beenthere:x-received:date:from:to:cc:message-id :in-reply-to:references:subject:mime-version:x-original-sender :reply-to:precedence:mailing-list:list-id:x-google-group-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe :content-type; bh=jVqOylWGUp9DL/I3qkQdRkrBZBpxMHnn4t2hePoryo0=; b=wynjKM2MHmJFxZMy8OCT4Ge0VEQErHIFzqxBm9SvG4F3HJqpyGJZff9pJx+ydSFNih nnHYI9KCToHWxfqpW6VPKAnZRuq9zv+H8zgigNFbxcyhvp5tTAn1pYvTPAoALxIWHZlh C1M8B1UH67aF3s9A4Qv6Z9/n7GXtyNkZQCqJjJpckxROrK39ORA4WIWNetWueI2si1Rv vhfEk0obff6Z5SVY9dnC1nLQPAVdBeoluYb9gZOsATV6/rjjZL/gcKy3AnmUljqW4JBE GIvfUUcTW3EZIkbRSlwQaRZXPTgd10meLUWxn2XP6Xty/5aZPKXlPIHeBRUuKwVyStzK v23A== X-Received: by 10.224.72.199 with SMTP id n7mr13890127qaj.5.1360094563270; Tue, 05 Feb 2013 12:02:43 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.11.204 with SMTP id s12ls128158qeb.11.gmail; Tue, 05 Feb 2013 12:02:42 -0800 (PST) X-Received: by 10.49.116.135 with SMTP id jw7mr2249961qeb.10.1360094562884; Tue, 05 Feb 2013 12:02:42 -0800 (PST) In-Reply-To: X-Original-Sender: akrzemi1@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:2741 Archived-At: ------=_Part_1772_14843462.1360094562219 Content-Type: text/plain; charset=ISO-8859-1 > > mixed assignment is illegal. Use one of the following instead: > > > > *oi = j; // if you want to alter the referred-to object > > oi = {j}; // if you want to rebind a reference > > > >> > > > > Copy constructor and copy assignment are shallow: they only (re)bind a > > reference. Other operations are deep: this includes comparison (mixed or > > homogenous) > > > > Is optional a RegularType? > I am not sure how to answer the question. Different people have slightly different expectations of a regular type. optional has: - default ctor - destructor - copy/move constructor (shallow) - copy/move assignment (shallow) - equality comparison (deep, provided that T is comparable) - it is not swappable yet, but I intend to add a shallow swap I am not not sure what semantic requirements a RegularType requires. The value compared by operator== is not under control of the optional object: it can change "asynchronously". Also the copy/move operations are not compatible with operator==: the former are shallow, the latter is deep. -- --- 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/?hl=en. ------=_Part_1772_14843462.1360094562219 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
> mixed assignment is i= llegal. Use one of the following instead:
>
> *oi =3D j; // if you want to alter the referred-to object
> oi =3D {j}; // if you want to rebind a reference
>
>>
>
> Copy constructor and copy assignment are shallow: they only (re)bi= nd a
> reference. Other operations are deep: this includes comparison (mi= xed or
> homogenous)
>

Is optional<T&> a RegularType?

I am not sure how to answer the question. Differe= nt people have slightly different expectations of a regular type.
option= al<T&> has:
  • default ctor
  • destructor
    • copy/move constructor (shallow)
  • copy/move assignment (shallow)
  • equality comparison (deep, provided that T is comparable)
  • it = is not swappable yet, but I intend to add a shallow swap
I am = not not sure what semantic requirements a RegularType requires. The value c= ompared by operator=3D=3D is not under control of the optional object: it c= an change "asynchronously". Also the copy/move operations are not compatibl= e with operator=3D=3D: the former are shallow, the latter is deep.
 

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