220 37289 article Path: news.gmane.org!.POSTED!not-for-mail From: Jefferson Carpenter Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Pointer overload for || Date: Sun, 11 Mar 2018 04:01:41 -0500 Lines: 107 Approved: news@gmane.org Message-ID: References: <1fea07df-46a6-4df2-865a-849be8f8d129@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1520758785 15475 195.159.176.226 (11 Mar 2018 08:59:45 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 11 Mar 2018 08:59:45 +0000 (UTC) User-Agent: Mozilla/5.0 (Windows NT 6.2; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDMNDCNA64OBB6XASPKQKGQEJHIHHOA@isocpp.org Sun Mar 11 09:59:41 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-it0-f70.google.com ([209.85.214.70]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1euwpR-0003uo-6s for gclcip-std-proposals@m.gmane.org; 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([2601:441:8680:4631:ecd0:a4aa:6a04:1146]) by smtp.gmail.com with ESMTPSA id 30sm3290224iop.73.2018.03.11.01.01.44 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 11 Mar 2018 01:01:44 -0800 (PST) In-Reply-To: Content-Language: en-US X-Original-Sender: jeffersonCarpenter2@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=Duqp7hFQ; spf=pass (google.com: domain of jeffersoncarpenter2@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=jeffersoncarpenter2@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=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:37289 Archived-At: Indeed, that's very nice. On 3/11/2018 3:58 AM, Ga=C5=A1per A=C5=BEman wrote: > There is a binary form of the conditional operator that is a gnu extensio= n: >=20 > void foo(int *x) { > x =3D x?:new int; > } >=20 > It's defined as >=20 > CEXPR ?: FEXPR; >=20 > and rewritten into >=20 > { > auto&& x =3D CEXPR; > if (x) { return x; } else { return FEXPR; } > } >=20 > Perhaps you could propose that instead, as it's far more general. It's a > GNU extension because certain macros (assert comes to mind) are much easi= er > to implement if you have it. >=20 > G >=20 >=20 >=20 >=20 > On Sun, Mar 11, 2018, 08:38 wrote: >=20 >> Not sure how this will be received -- I haven't posted here much. Just >> thought it would be worth mentioning this idea. >> >> Suppose you have an API that you want to optionally allocate storage for >> your user. They can either pass in a pointer to some existing allocated >> space, or pass in a null pointer and space is allocated for them. >> >> void foo(int *x) { >> if (x =3D=3D nullptr) { >> x =3D new int; >> } >> // etc. >> } >> >> Just figured it would be a decent idea if the || operator received a >> pointer overload. Then you could write the more succinct >> >> void foo(int *x) { >> x =3D x || new int; >> } >> >> or even (ducks for cover) >> >> void foo(int *x) { >> x ||=3D new int; >> } >> >> would be nice. >> >> Currently, if I am not mistaken, || (excluding user-defined overloads) i= s >> a boolean-only operator. It is indeed the case that nullptr is the only >> value that becomes false when cast to a boolean, and all other pointer >> values become true. So I don't see how adding an || overload for pointe= rs >> would break any existing code. >> >> The main thing that would make this a no-go would be if the semantics of >> || required that both operands be evaluated -- whether or not the left-h= and >> one is false. Then the whole point as I see it would be lost - the abov= e >> examples would merely leak memory. >> >> - Jefferson Carpenter >> >> -- >> You received this message because you are subscribed to the Google Group= s >> "ISO C++ Standard - Future Proposals" group. >> To unsubscribe from this group and stop receiving emails from it, send a= n >> 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/1fea07df-46a6-4df2- >> 865a-849be8f8d129%40isocpp.org >> >> . >> >=20 --=20 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 e= mail 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/f2c867ca-f34f-e3ad-1f3e-b8aabc8e13b0%40gmail.com= .. .