220 2731 <8d57e9e9-e4cc-441c-abeb-e6526531fad5@isocpp.org> article Path: news.gmane.org!not-for-mail From: =?UTF-8?Q?Andrzej_Krzemie=C5=84ski?= Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: optional references -- take 2 Date: Mon, 4 Feb 2013 11:23:07 -0800 (PST) Lines: 158 Approved: news@gmane.org Message-ID: <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_408_17593010.1360005787933" X-Trace: ger.gmane.org 1360005793 13175 80.91.229.3 (4 Feb 2013 19:23:13 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 4 Feb 2013 19:23:13 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDT2DGOJ34DBBHMVYCEAKGQEI5TZIAA@isocpp.org Mon Feb 04 20:23:34 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-gg0-f197.google.com ([209.85.161.197]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1U2RdZ-0002sU-Kw for gclcip-std-proposals@m.gmane.org; Mon, 04 Feb 2013 20:23:29 +0100 Original-Received: by mail-gg0-f197.google.com with SMTP id k5sf1207748ggn.0 for ; Mon, 04 Feb 2013 11:23:10 -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:message-id: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=xJNPNie7E3WwbVGbrfF1tXa1JNoqGosaC8OrSFc8X2g=; b=elnEJCPQGPzH1dk//7nsgt9i20qWPdyos0JeqnkH27AZ4TPQYklKcBtWSEP1AJdEXx 70BPGwrNMakrZ77KyY9Y3/42NWCdGkmitCZi/BETQUCvV/0IEQZCRKG2dAb87w06Gw41 D2hnRYctsYHs10MG9y+yg9Xet49fg0XUwc06K4wm8XzmUKvtGHMpYcGpuA3GJX9YEO9w VuMY0e5KK4pJP1GwBk+uqfrG2aGpmd+CTxvllbpLX1nwOn7deTfeL6p7UBVq8g5TwBdn FSuE9SIcKJI2M6ru8ei02KrdqscZbMIkvrTeFdl7hMsGYwQVcF0kMjVu8rOZ80xdwc9b yLBA== X-Received: by 10.236.81.80 with SMTP id l56mr9050972yhe.16.1360005790384; Mon, 04 Feb 2013 11:23:10 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.16.37 with SMTP id c5ls1895819qed.80.gmail; Mon, 04 Feb 2013 11:23:08 -0800 (PST) X-Received: by 10.49.39.99 with SMTP id o3mr1831520qek.14.1360005788154; Mon, 04 Feb 2013 11:23:08 -0800 (PST) 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:2731 Archived-At: ------=_Part_408_17593010.1360005787933 Content-Type: text/plain; charset=ISO-8859-1 > > > I wanted to consult with people here one more thing about mixed relops. > > Assuming that we allow mixed relops for optional values, should we also > > provide them for optional references? > > > > int i = 9; > > optional oi = i; > > return oi == i; // should it work? > > > > Just to be clear, does it compare the values, or the ref? > The values. > > ie > > int i = 9; > optional oi = i; > int j = 9; > return oi == j; // also true? > This returns true. > > > And does this follow whichever rules of set-the-value or set-the-ref > you are choosing? > > ... > j = 5; > oi = j; > 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 > > cout << i; // prints... 5? 9? > Copy constructor and copy assignment are shallow: they only (re)bind a reference. Other operations are deep: this includes comparison (mixed or homogenous) > > > Sorry to bring up the optional & discussion again. I really just > wondered whether it was consistent with assignment, whichever way it > goes. I started another thread, in case people want to comment on optional references. You can find the updated proposal here: http://kojot.sggw.waw.pl/~akrzemi1/optional/tr2.optional.proposal.html Optional references are at the end as an auxiliary proposal. Regards, &rzej -- --- 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_408_17593010.1360005787933 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
> I wanted to = consult with people here one more thing about mixed relops.
> Assuming that we allow mixed relops for optional values, should we= also
> provide them for optional references?
>
> int i =3D 9;
> optional<int&> oi =3D i;
> return oi =3D=3D i; // should it work?
>

Just to be clear, does it compare the values, or the ref?

The values.
 

ie

int i =3D 9;
optional<int&> oi =3D i;
int j =3D 9;
return oi =3D=3D j;  // also true?

This returns true.
 


And does this follow whichever rules of set-the-value or set-the-ref
you are choosing?

...
j =3D 5;
oi =3D j;

mixed assignment is illegal. Use one of the follo= wing instead:

*oi =3D j; // if you want to alter the referred-to obj= ect
oi =3D {j}; // if you want to rebind a reference
 
=

cout << i;  // prints... 5? 9?

Copy constructor and copy assignment are shallow:= they only (re)bind a reference. Other operations are deep: this includes c= omparison (mixed or homogenous)
 


Sorry to bring up the optional & discussion again.  I really j= ust
wondered whether it was consistent with assignment, whichever way it
goes.

I started another thread, in case people want to comm= ent on optional references. You can find the updated proposal here: http://= kojot.sggw.waw.pl/~akrzemi1/optional/tr2.optional.proposal.html
Optional= references are at the end as an auxiliary proposal.

Regards,
&am= p;rzej

--
 
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