220 20630 <09547076-d049-4d87-acc3-b851e6518942@isocpp.org> 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 10:38:58 -0700 (PDT) Lines: 163 Approved: news@gmane.org Message-ID: <09547076-d049-4d87-acc3-b851e6518942@isocpp.org> References: <4c3e2ee7-2159-4e93-a439-7d5c94c38c9c@isocpp.org> <6a0ad653-4764-483b-afb5-74d444be15d9@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_284_642464533.1442943538915" X-Trace: ger.gmane.org 1442943545 2981 80.91.229.3 (22 Sep 2015 17:39:05 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Tue, 22 Sep 2015 17:39:05 +0000 (UTC) Cc: joewoodbury@gmail.com To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCBMHLUN7EEBBM5EQ2YAKGQEJHMQFEI@isocpp.org Tue Sep 22 19:39:04 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pd0-f197.google.com ([209.85.192.197]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ZeRWw-0000Mj-HG for gclcip-std-proposals@m.gmane.org; Tue, 22 Sep 2015 19:39:02 +0200 Original-Received: by pdbpr5 with SMTP id pr5sf25979423pdb.2 for ; Tue, 22 Sep 2015 10:39:01 -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=GCzxwn0DJujgnVf+ivuhTFnXKqmQbkmQ4G7Q++kbT6I=; b=tLardDEAYxa9jviRl8bXfL4qASrjAtVN6XNBpgpEhw8e8IObphoRjbMnK9pzt6dGTx PDdsLLRf/JPaSJtmIWjJoneL9f7+qpeo3dA1SPGJzwu/i+Xltu6vIQGIwwCerlxDGIOt zV6D0RFq7cqppmkZdJLmf/3I9/kw3n0h6GwOEQoV8NQ9OkeCZvkgREfLfGBcqjJWk8rc 8xVuYlw5QQyDiE2FUZQA59doCh6geWKk1jllwlxMf9DdPawQnYu364HxYFbDTTy/JanI v8/u0CqVhBaYT0/xgxcaQABqggTEZ/QaW7x4IeUGFQFzF5Q2yIQtEOPMrD5OD+tuJ61k c9lQ== 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=GCzxwn0DJujgnVf+ivuhTFnXKqmQbkmQ4G7Q++kbT6I=; b=Wr4qvD/IxBt2/XErM7cRm3gUVd2722A1/O3SRI/nydw3+eo2W3ITp4IHcswFdQSwru 6n+WVfpHpT7fKQxmEUa1IiivmLM+OV+EFvgarPSphTPUHOrl+oVqj8ZEEAtffVMfMjHn pSbqf8Sz8etWp8GW1yxGY1sM9VVqvF8wcnzp5Ezv6wxTiJ1Qesrz30CReYVGD0mvF6sj 8ljsGSzls3lNeLdoINf/kG32VqGN1w7rlKLbQfZkQ9b4yigfyLeICH3Qcm0zrWj+wyMd giWr9bAKpPdnpaResFuYrrRUVHV3b9Sel7cWpQaQppHt7aKkHd7eVESM27TOEZSuEv7+ aYxA== X-Gm-Message-State: ALoCoQmzFwtmTJOa5iIY+3HFKjwvDVJ4n3fObvoER94sa2mS5/Ci7B3t4e0DcWjse12ettbvMRQ1 X-Received: by 10.66.182.162 with SMTP id ef2mr23055644pac.35.1442943541423; Tue, 22 Sep 2015 10:39:01 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.132.84 with SMTP id g81ls199067iod.98.gmail; Tue, 22 Sep 2015 10:38:59 -0700 (PDT) X-Received: by 10.50.45.100 with SMTP id l4mr210980igm.9.1442943539650; Tue, 22 Sep 2015 10:38:59 -0700 (PDT) In-Reply-To: <6a0ad653-4764-483b-afb5-74d444be15d9@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:20630 Archived-At: ------=_Part_284_642464533.1442943538915 Content-Type: multipart/alternative; boundary="----=_Part_285_1814952225.1442943538915" ------=_Part_285_1814952225.1442943538915 Content-Type: text/plain; charset=UTF-8 First, I didn't say it was necessary nor even imply it; I said it would be "a nice solution" Second, my examples were intentionally trivial. Thus if I wrote int val = connection ?: 5; your solution wouldn't work. On Tuesday, September 22, 2015 at 10:15:58 AM UTC-7, Nicol Bolas wrote: > > On Tuesday, September 22, 2015 at 1:03:47 PM UTC-4, 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); >> > > Or you could have just written: > > if(connection) connection->SendMessage(msg); > > That requires only one or two extra keystrokes. Both of these are > restricted to single lines to be executed. > > 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); >> > > Ultimately, I don't think good coding practices make this as necessary as > you let on. Most of the time, if you have a pointer, you know it's valid. > It was checked for validity when you received it, and you don't want to > constantly check to see if the thing that was valid before remains valid > now. > > We don't need to use up precious syntax for a relatively infrequent case. > > Likewise: >> >> bool success = connection ?: false; >> > > Also easily done like this: > > auto success = bool{connection}; > > `explicit operator bool` will be called here, since you explicitly asked > for it. > -- --- 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_285_1814952225.1442943538915 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
First, I didn't say it was necessary nor even imply it= ; I said it would be "a nice solution"

Second, my examples= were intentionally trivial.

Thus if I wrote

int val =3D conn= ection ?: 5;

your solution wouldn't work.


On Tuesday,= September 22, 2015 at 10:15:58 AM UTC-7, Nicol Bolas wrote:
On Tuesday, September 22, 20= 15 at 1:03:47 PM UTC-4, joewo...@gmail.com wrote:
Checking for null and then doing on= e thing is a common task. null-conditional and null-coalescing operators wo= uld be a nice solution.

For example, given the following pointer:
=C2=A0=C2=A0=C2=A0 unique_ptr<Connection> connection;

Thi= s 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(m= sg);
=C2=A0=C2=A0=C2=A0 }

A nice alternative would be:

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

Or you could have just written:

if(connection) connection->SendMessage(msg);

That requires only one or two extra keystrokes. Both of thes= e are restricted to single lines to be executed.

I've had situations where i= f anything resolves to false on the left, this ?: would be useful.

O= r even better, to carry the concept forward:

=C2=A0=C2=A0=C2=A0 conn= ection?->SendMessage(msg);

Ultimately, I = don't think good coding practices make this as necessary=20 as you let on. Most of the time, if you have a pointer, you know it's= =20 valid. It was checked for validity when you received it, and you don't= =20 want to constantly check to see if the thing that was valid before=20 remains valid now.

We don't need to use up precious syntax for a= relatively infrequent case.

Likewise:

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

Also easily done li= ke this:

auto success =3D bool{connection};

`explicit operator bool` will be = called here, since you explicitly asked for it.

--

---
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.
Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposals/<= /a>.
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