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[209.85.220.41]) by mx.google.com with SMTPS id j10sor1445776pfe.78.2018.03.11.00.59.07 for (Google Transport Security); Sun, 11 Mar 2018 00:59:07 -0800 (PST) Received-SPF: pass (google.com: domain of gasper.azman@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; X-Received: by 10.98.196.84 with SMTP id y81mr4243629pff.11.1520758746586; Sun, 11 Mar 2018 00:59:06 -0800 (PST) Original-Received: by 10.236.133.141 with HTTP; Sun, 11 Mar 2018 00:58:46 -0800 (PST) In-Reply-To: <1fea07df-46a6-4df2-865a-849be8f8d129@isocpp.org> X-Original-Sender: gasper.azman@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=XpBxEq7f; spf=pass (google.com: domain of gasper.azman@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=gasper.azman@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:37288 Archived-At: --94eb2c11d754e1238605671f3c11 Content-Type: text/plain; charset="UTF-8" There is a binary form of the conditional operator that is a gnu extension: void foo(int *x) { x = x?:new int; } It's defined as CEXPR ?: FEXPR; and rewritten into { auto&& x = CEXPR; if (x) { return x; } else { return FEXPR; } } 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 easier to implement if you have it. G On Sun, Mar 11, 2018, 08:38 wrote: > 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 == nullptr) { > x = 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 = x || new int; > } > > or even (ducks for cover) > > void foo(int *x) { > x ||= new int; > } > > would be nice. > > Currently, if I am not mistaken, || (excluding user-defined overloads) is > 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 pointers > 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-hand > one is false. Then the whole point as I see it would be lost - the above > examples would merely leak memory. > > - Jefferson Carpenter > > -- > 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/1fea07df-46a6-4df2- > 865a-849be8f8d129%40isocpp.org > > . > -- 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/CAANG%3DkVsGNaXGZLtbNm%3D9cJxjLXwu0cgL%3Dp_kYa1TCRSKfNCvg%40mail.gmail.com. --94eb2c11d754e1238605671f3c11 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
There is a binary form of the condi= tional operator that is a gnu extension:

void foo(= int *x) {
=C2=A0 x =3D x?:new int;
}

It's defined as

CEXPR ?: FEXPR;

and rewritten into

{
= =C2=A0 =C2=A0auto&& x =3D CEXPR;
=C2=A0 =C2=A0if (x) { re= turn x; } else { return FEXPR; }
}

Perha= ps 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 easie= r to implement if you have it.

G




On Sun, Mar 11, 2018, 08:38 <jeffersoncarpenter2@gmai= l.com> wrote:
Not sure how this will be received -- I haven't posted here mu= ch.=C2=A0 Just thought it would be worth mentioning this idea.

Suppo= se you have an API that you want to optionally allocate storage for your us= er.=C2=A0 They can either pass in a pointer to some existing allocated spac= e, or pass in a null pointer and space is allocated for them.

void f= oo(int *x) {
=C2=A0 if (x =3D=3D nullptr) {
=C2=A0=C2=A0=C2=A0 x =3D = new int;
=C2=A0 }
=C2=A0 // etc.
}

Just figured it would be= a decent idea if the || operator received a pointer overload.=C2=A0 Then y= ou could write the more succinct

void foo(int *x) {
=C2=A0 x =3D = x || new int;
}

or even (ducks for cover)

void foo(int *x)= {
=C2=A0 x ||=3D new int;
}

would be nice.

Currently, = if I am not mistaken, || (excluding user-defined overloads) is a boolean-on= ly operator.=C2=A0 It is indeed the case that nullptr is the only value tha= t becomes false when cast to a boolean, and all other pointer values become= true.=C2=A0 So I don't see how adding an || overload for pointers woul= d 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-hand one is false.=C2=A0 Then the whole point a= s I see it would be lost - the above examples would merely leak memory.
=
- Jefferson Carpenter

--
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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/1fea07df-46a6-4df2-865a-849be8f8d129%40isocpp.org.

--
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