220 27259 article Path: news.gmane.org!not-for-mail From: gmisocpp@gmail.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: loop continuation code Date: Mon, 25 Jul 2016 17:57:38 -0700 (PDT) Lines: 231 Approved: news@gmane.org Message-ID: References: <2f575934-e078-411c-9c8a-c2996da7609d@isocpp.org> <28358863-5be0-401a-893a-0ae5385156c2@isocpp.org> <8ee79066-43c5-4624-8fb5-01172eb36d29@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_1671_2115848116.1469494659019" X-Trace: ger.gmane.org 1469494673 8856 80.91.229.3 (26 Jul 2016 00:57:53 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Tue, 26 Jul 2016 00:57:53 +0000 (UTC) Cc: gmisocpp@gmail.com To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCM3TRNUXUDBBBHL3K6AKGQEUHDGO6Y@isocpp.org Tue Jul 26 02:57:44 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pf0-f200.google.com ([209.85.192.200]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1bRqgp-00058R-6b for gclcip-std-proposals@m.gmane.org; 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Mon, 25 Jul 2016 17:57:41 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.36.75.133 with SMTP id q127ls3894367ita.14.gmail; Mon, 25 Jul 2016 17:57:40 -0700 (PDT) X-Received: by 10.36.50.145 with SMTP id j139mr595013ita.9.1469494660053; Mon, 25 Jul 2016 17:57:40 -0700 (PDT) In-Reply-To: <8ee79066-43c5-4624-8fb5-01172eb36d29@isocpp.org> X-Original-Sender: gmisocpp@gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Spam-Checked-In-Group: std-proposals@isocpp.org 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:27259 Archived-At: ------=_Part_1671_2115848116.1469494659019 Content-Type: multipart/alternative; boundary="----=_Part_1672_1187900692.1469494659019" ------=_Part_1672_1187900692.1469494659019 Content-Type: text/plain; charset=UTF-8 On Tuesday, July 26, 2016 at 12:01:38 PM UTC+12, Sean Middleditch wrote: > > Or just remove the variable i from the loop entirely because it's unused > in the loop body, thus reducing the for statement to: > > for(; pUnicast != nullptr; pUnicat = pUnicast->Next) > > Not that a multi-statement increment wouldn't be useful, but this code > snippet is a pretty terrible motivating example. Sorry Glenn! :) > It's just some code I saw on reddit. But c'mon, you're being as unimaginative here as I've been lazy in crimping some random code to demonstrate the use case! lol I'm not suggesting the need is desperate, but I have myself a few times in the past written loops where I've realised that I'd like to "continue early" a few times - much like returning early - to avoid complicating later code with logic just to avoid it being hit. But I'd still like to do something a bit more significant on each continue occasionally and not want to repeat that code or to have to try to shoe horn that logic into the increment statement of the loop or use a comma there where it just feels wrong and is too constrained. I don't think you need to be that imaginative to see that ;) but hey I'm sure you won't be alone in your opinion if you still don't agree. I perhaps should contact the author of the original code and see if they agree if this facility would encourage them to use it over goto. That would a be a little interesting to me. Thanks for your feedback. > > Anecdotally though (not that anyone cares, nor should you), I can't recall > a time I ever felt that I needed multiple loop incrementees without > eventually realizing that I was just writing my loop like an idiot. Or > missing an easily-written library facility to use with for-range iterator. > :) > > On Monday, July 25, 2016 at 8:08:23 AM UTC-7, Nicol Bolas wrote: >> >> >> for ( int i = 0; pUnicast != NULL; >> pUnicast = pUnicast->Next; i++) >> { >> Address address( (sockaddr_storage*) pUnicast->Address.lpSockaddr ); >> >> if ( !address.IsValid() ) >> continue; // goto the continue block below >> >> if ( address.IsLoopback() ) >> continue; >> >> if ( address.GetType() == ADDRESS_IPV6 && !address.IsGlobalUnicast() ) >> continue; >> >> addresses[numAddresses++] = address; >> >> if ( numAddresses >= maxAddresses ) >> break; >> } >> >> This puts all of the iteration logic in the same place: the `for` >> statement itself. So if you want to see what happens on each loop, you >> don't have to look at both the top and the bottom of the `for` statement. >> > -- 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/c0a2a265-9128-490c-b80e-d9f7438df92a%40isocpp.org. ------=_Part_1672_1187900692.1469494659019 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable


On Tuesday, July 26, 2016 at 12:01:38 PM UTC+12, S= ean Middleditch wrote:
Or just= remove the variable i from the loop entirely because it's unused in th= e loop body, thus reducing the for statement to:

=C2=A0 = =C2=A0 for(; pUnicast !=3D nullptr; pUnicat =3D pUnicast->Next)

=
Not that a multi-statement increment wouldn't be useful= , but this code snippet is a pretty terrible motivating example. Sorry Glen= n! :)

It's just= some code I saw on reddit. But c'mon, you're being as unimaginativ= e here as I've been lazy in crimping some random code to demonstrate=C2= =A0the=C2=A0use case! lol
I'm not suggesting the need=C2=A0is= desperate, but I have myself a few times in the past written loops where I= 've realised that I'd like to "continue early" a few time= s - much like returning early - to avoid complicating later code=C2=A0with = logic=C2=A0just to avoid it being hit. But I'd still like to do somethi= ng a bit more significant on each continue occasionally and not want to rep= eat that code or=C2=A0to have to try to=C2=A0shoe horn that logic into the = increment statement of the loop or use=C2=A0a comma there where it=C2=A0jus= t feels wrong and is too constrained.

I don't = think you need to be=C2=A0that imaginative to see that ;)=C2=A0but hey I= 9;m sure you won't be alone in your opinion if you still don't agre= e. I perhaps should contact the author of the original code and see if they= agree if this facility would encourage them to use it over goto. That woul= d a be a little interesting to me.

Thanks for your= feedback.

=C2=A0

Anecdotally though (not th= at anyone cares, nor should you), I can't recall a time I ever felt tha= t I needed multiple loop incrementees without eventually realizing that I w= as just writing my loop like an idiot. Or missing an easily-written library= facility to use with for-range iterator. :)

On Monday, = July 25, 2016 at 8:08:23 AM UTC-7, Nicol Bolas wrote:

for<= /span> ( int i =3D 0; pUnicast !=3D NULL;
=C2=A0 pUnicast =3D pUnicast->Next; i++= )
{
=C2= =A0 =C2=A0Address address( (sockaddr_storage*) pUnicast->A= ddress.lpSockaddr );

=C2=A0 =C2= =A0if ( !address.IsValid() )
=C2=A0 =C2=A0 = =C2=A0 continue; // goto the continue blo= ck below

=C2=A0 =C2=A0if ( address.IsLoopback<= /span>() )=
=C2=A0 =C2=A0 =C2=A0 continue;

=C2=A0 = =C2=A0if ( address.Get= Type() =3D= =3D ADDRESS_IPV6 && !address.IsGlobalUnicas= t() )
=C2=A0 =C2=A0 =C2=A0 continue;

=C2=A0= =C2=A0addresses[numAddresses++] <= span style=3D"color: rgb(102, 102, 0);">=3D address;

=C2=A0 =C2=A0if ( numAddresses >=3D maxAddresses )
=C2=A0 =C2=A0 =C2=A0 break;
}

This puts all of the iteration lo= gic in the same place: the `for` statement itself. So if you want to see wh= at happens on each loop, you don't have to look at both the top and the= bottom of the `for` statement.

--
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/c0a2a265-9128-490c-b80e-d9f7438df92a= %40isocpp.org.
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