220 20678 article Path: news.gmane.org!not-for-mail From: joewoodbury@gmail.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Null -conditional and -coalescing operators Date: Tue, 22 Sep 2015 17:34:20 -0700 (PDT) Lines: 115 Approved: news@gmane.org Message-ID: References: <4c3e2ee7-2159-4e93-a439-7d5c94c38c9c@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_665_1464794827.1442968460559" X-Trace: ger.gmane.org 1442968465 32241 80.91.229.3 (23 Sep 2015 00:34:25 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 23 Sep 2015 00:34:25 +0000 (UTC) Cc: joewoodbury@gmail.com To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCBMHLUN7EEBBDPHQ6YAKGQEHQZYUXA@isocpp.org Wed Sep 23 02:34:25 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-qg0-f69.google.com ([209.85.192.69]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ZeY0u-0000kd-Ow for gclcip-std-proposals@m.gmane.org; Wed, 23 Sep 2015 02:34:24 +0200 Original-Received: by qgev79 with SMTP id v79sf9560971qge.0 for ; Tue, 22 Sep 2015 17:34:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=date:from:to:cc:message-id:in-reply-to:references:subject :mime-version:content-type: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=Ze6UPu7Zl7ER+Fs09Tnj2YthKh4sbe93Cc+BqKp/fIQ=; b=XUMXNykYvR74a3VCSrFCyFe9augqnn8alQwNTV/DWSJ7krH41PXPVWBhpHN5xuLzMs /80BYjuE+uooy1a2mQyDllFCtSKT8yYdc0Bm3XG8ZyFaMrePO5TBsiQb9RBeRtU3g1e9 Qbjd9SWcnCtXh2hukD1IfUer1FIjJ5d0KZYVT0zs8vI3BqBvmqCDa5aAXGZYSKfjdWz4 ZC16ETvxb0h83RTzmn1vdTaCMn6nf7yImn9AVGa435I8XD/rlpsLcSpOHiG9Fm1/84f0 7BCXmtwVncLBjzP7Rfyc2g73HrytBO9Z9f9Rsg+d9qb8CxeG/t34CtfIjVGfUZbGFVl0 Ji1Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to:cc:message-id:in-reply-to :references:subject:mime-version:content-type: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=Ze6UPu7Zl7ER+Fs09Tnj2YthKh4sbe93Cc+BqKp/fIQ=; b=fmcPRVcFlAwyVMbGw3ZaSE5jzHvghx+9bOVNfqUITNQ6LriUfsIxiGqac3/TpEm+3S XYbcmBsFtJag6qNsZ0scXIdZ+XRtm0eCHeSgNkwh6kYMN6ZrOtzub7gP/B47l4Fw4fX5 cUGwKUUsjrBUIos5wT9uuSs8lsDQD6QCyf3xg7mN4crKmHFcDdXoQq6kVjxy3eFoDxIi NN/VACuG7Zd8VD1RDax+/bd8cmNKB9gsLiN20eBzNtbs2Dh0XazN9JApVxz5dyN8uSU3 nc6Ugibt645oVkNH6quxyeTrlrsQ6zLWNhv6qvLCzmEzCgwlp7OeiZTmlRDJK10uPzLs kYGQ== X-Gm-Message-State: ALoCoQkIAwPgY50iaw2LcDkouH+36FVyqewewVjzrLQpg6eKQ6GGk/fJuXQPQkOjNhzE9YUseXNb X-Received: by 10.13.202.195 with SMTP id m186mr25882851ywd.55.1442968463628; Tue, 22 Sep 2015 17:34:23 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.50.41.8 with SMTP id b8ls297631igl.9.canary; Tue, 22 Sep 2015 17:34:21 -0700 (PDT) X-Received: by 10.50.143.5 with SMTP id sa5mr8103igb.1.1442968461584; Tue, 22 Sep 2015 17:34:21 -0700 (PDT) In-Reply-To: <4c3e2ee7-2159-4e93-a439-7d5c94c38c9c@isocpp.org> X-Original-Sender: joewoodbury@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:20678 Archived-At: ------=_Part_665_1464794827.1442968460559 Content-Type: multipart/alternative; boundary="----=_Part_666_883898929.1442968460560" ------=_Part_666_883898929.1442968460560 Content-Type: text/plain; charset=UTF-8 Here in interesting example I just encountered: strLen is passed into a function along with pStr. After nullptr checks, the following is done: size_t tmpStrLen = wcslen(pStr); if (strLen > tmpStrLen) strLen = tmpStrLen; Using the ?: operator, you could do: strLen = wcslen(pStr) < strLen ?: strLen; Again, a trivial example, but one in actual code. On Tuesday, September 22, 2015 at 10:03:47 AM UTC-7, joewo...@gmail.com wrote: > > Checking for null and then doing one thing is a common task. > null-conditional and null-coalescing operators would be a nice solution. > > For example, given the following pointer: > > unique_ptr connection; > > This may happen: > > if (connection) > { > connection->sendMessage(msg); > } > > A nice alternative would be: > > connection ?: connection->SendMessage(msg); > > I've had situations where if anything resolves to false on the left, this > ?: would be useful. > > Or even better, to carry the concept forward: > > connection?->SendMessage(msg); > > Likewise: > > bool success = connection ?: false; > > > -- --- 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/. ------=_Part_666_883898929.1442968460560 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Here in interesting example I just encountered:

str= Len is passed into a function along with pStr. After nullptr checks, the fo= llowing is done:

=C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0= =C2=A0 size_t tmpStrLen =3D wcslen(pStr);
=C2=A0=C2=A0=C2=A0 =C2=A0=C2= =A0=C2=A0 =C2=A0=C2=A0=C2=A0 if (strLen > tmpStrLen)
=C2=A0=C2=A0=C2= =A0 =C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 strLen =3D tmp= StrLen;

Using the ?: operator, you could do:

=C2=A0=C2=A0=C2= =A0 =C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 strLen =3D wcslen(pStr) < strL= en ?: strLen;

Again, a trivial example, but one in actual code.
<= br>

On Tuesday, September 22, 2015 at 10:03:47 AM UTC-7, joewo...@gm= ail.com wrote:
Checking for null and then doing one thing is a common task. null-conditio= nal and null-coalescing operators would be a nice solution.

For exam= ple, given the following pointer:

=C2=A0=C2=A0=C2=A0 unique_ptr<C= onnection> connection;

This may happen:

=C2=A0=C2=A0=C2=A0= if (connection)
=C2=A0=C2=A0=C2=A0 {
=C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0= =C2=A0 connection->sendMessage(msg);
=C2=A0=C2=A0=C2=A0 }

A ni= ce alternative would be:

=C2=A0=C2=A0=C2=A0 connection ?: connection= ->SendMessage(msg);

I've had situations where if anything res= olves to false on the left, this ?: would be useful.

Or even better,= to carry the concept forward:

=C2=A0=C2=A0=C2=A0 connection?->Se= ndMessage(msg);

Likewise:

=C2=A0=C2=A0=C2=A0 bool success =3D= connection ?: false;


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