220 21344 article Path: news.gmane.org!not-for-mail From: Vlad from Moscow Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Conversion from lvalue to rvalue Date: Tue, 6 Oct 2015 04:06:49 -0700 (PDT) Lines: 173 Approved: news@gmane.org Message-ID: References: <0a839ad1-1a3c-4323-a20c-3cd910ec08f4@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_35_119634074.1444129609270" X-Trace: ger.gmane.org 1444129614 21358 80.91.229.3 (6 Oct 2015 11:06:54 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Tue, 6 Oct 2015 11:06:54 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCXLLRHD7IDRBSWWZ2YAKGQEH2P5Z5I@isocpp.org Tue Oct 06 13:06:53 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pa0-f70.google.com ([209.85.220.70]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ZjQ57-0007GI-6I for gclcip-std-proposals@m.gmane.org; Tue, 06 Oct 2015 13:06:53 +0200 Original-Received: by pablk4 with SMTP id lk4sf122114616pab.1 for ; Tue, 06 Oct 2015 04:06:52 -0700 (PDT) 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: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=Vbcd0IpV5uVxTlzV2goAiUHb0T+ASe0Rqk6+gwvEKUE=; b=WWt/rPBnYZmW0EFVPtZCr8+0W7uQmamEnD4+q18tgV0lHMQIV+qjOh/Na9K8MXnS+X U4bqV8VnST8Xu0iSPBxa3Pc4l4lOs5Y/8Twgbzf+uvOAqquLbSVPswCOvSRZJezHZvlP 4TeiBG80QjYfs9QogVaPyd8A/8ap/RLS1DWHwkMLiwp9qMyJdET/CzW3Uelsbf0TNai4 r9sjw+/EKUGLy1lqyk/2rSuE2RJyTFDNrrpBmXSrGXq4/OMUQ5fcu48+0bwgvkIgofw9 Fkjf7ff+cmjw1YrGel7R7kQHRJ61xxnKblHCtc0/mItX/gU2soB+clLgjuj0Axy44DSe EKjg== X-Gm-Message-State: ALoCoQnldawdeBK/5odIRdHDks+Cos95ws1Ov2LBoUE03aG3D2C2zMNBhZtma2qz/LxaYVEHyE4T X-Received: by 10.66.158.229 with SMTP id wx5mr31264088pab.3.1444129611965; Tue, 06 Oct 2015 04:06:51 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.160.67 with SMTP id j64ls1961284ioe.3.gmail; Tue, 06 Oct 2015 04:06:50 -0700 (PDT) X-Received: by 10.50.79.195 with SMTP id l3mr76371igx.11.1444129610304; Tue, 06 Oct 2015 04:06:50 -0700 (PDT) In-Reply-To: <0a839ad1-1a3c-4323-a20c-3cd910ec08f4@isocpp.org> X-Original-Sender: vlad.moscow@mail.ru 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:21344 Archived-At: ------=_Part_35_119634074.1444129609270 Content-Type: multipart/alternative; boundary="----=_Part_36_1099146795.1444129609270" ------=_Part_36_1099146795.1444129609270 Content-Type: text/plain; charset=UTF-8 On Tuesday, October 6, 2015 at 1:56:04 PM UTC+3, Vlad from Moscow wrote: > > > On Monday, October 5, 2015 at 11:24:39 PM UTC+3, Vlad from Moscow wrote: >> >> One of methods to convert lvalue to rvalue is to use the functional of >> explicit conversion. >> >> Compare these two examples >> >> //... >> >> int main() >> { >> { >> int a = 10; >> int b = 5; >> >> std::tie( a, b ) = std::minmax( a, b ); >> std::cout << "a = " << a << ", b = " << b << std::endl; >> } >> { >> int a = 10; >> int b = 5; >> >> std::tie( a, b ) = std::minmax( int { a }, int { b } ); >> std::cout << "a = " << a << ", b = " << b << std::endl; >> } >> } >> >> The out put correspondingly is >> >> a = 5, b = 5 >> a = 5, b = 10 >> >> I am suggesting to use the following general syntax >> >> std::tie( a, b ) = std::minmax( auto( a ), auto( b ) ); >> >> > A simplified example that demonstrates the idea > > #include > > void f( int &&x ) { std::cout << "f( int &&( " << x << " ) )\n"; } > void f( int &x ) { std::cout << "f( int &( " << x << " ) )\n"; } > > int main() > { > int x = 3; > > f( x ); > f( 3 ); > } > > So in the code above I want to substitute the call f( 3 ) for > > f( auto( x ) ); > > > I think that in the preceding example l f( auto( 3 ) ); auto( 3 ) should not have any effect. Or more interesting example #include void f( int &&x ) { std::cout << "f( int &&( " << x << " ) )\n"; } void f( int &x ) { std::cout << "f( int &( " << x << " ) )\n"; } int main() { int x = 3; int y = 5; f( x < y ? x : y ); f( auto( x < y ? x : y ) ); } -- --- 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_36_1099146795.1444129609270 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable

On Tuesday, October 6, 2015 at 1:56:04 PM UTC+3, Vlad from Moscow w= rote:

On Monday, October 5, 2015 at 11:24:3= 9 PM UTC+3, Vlad from Moscow wrote:
One of methods to convert=C2=A0lvalue to rvalue is to use the= functional of explicit conversion.

Compare these = two examples

//...

int ma= in()
{
{
=C2=A0=C2=A0=C2=A0 int a =3D 10;
=C2=A0=C2=A0=C2=A0 in= t b =3D 5;
=C2=A0=C2=A0=C2=A0
=C2=A0=C2=A0=C2=A0 std::tie( a, b ) = =3D std::minmax( a, b );
=C2=A0=C2=A0=C2=A0 std::cout << "a = =3D " << a << ", b =3D " << b << std= ::endl;
}
{
=C2=A0=C2=A0=C2=A0 int a =3D 10;
=C2=A0=C2=A0=C2=A0= int b =3D 5;
=C2=A0=C2=A0=C2=A0
=C2=A0=C2=A0=C2=A0 std::tie( a, b )= =3D std::minmax( int { a }, int { b } );
=C2=A0=C2=A0=C2=A0 std::cout &= lt;< "a =3D " << a << ", b =3D " <<= ; b << std::endl;
}
}

The out=C2=A0put= correspondingly is

a =3D 5, b =3D 5
a =3D 5, b= =3D 10

I am suggesting to use the following gener= al syntax

=C2=A0=C2=A0=C2=A0 std::tie( a, b ) =3D = std::minmax(=C2=A0auto( a ),=C2=A0auto( b=C2=A0) );


A simplified example that demonstrates the ide= a

#include <iostream>

void f( int &&x ) { std::cout << "f( int &&( = " << x << " ) )\n"; }
void f(=C2=A0int &x= ) { std::cout << "f(=C2=A0int &( " << x <<= " ) )\n"; }

int main()
{
=C2=A0= =C2=A0=C2=A0 int x =3D 3;

=C2=A0=C2=A0=C2=A0 f= ( x );
=C2=A0=C2=A0=C2=A0 f( 3 );
}=C2=A0=C2=A0=C2=A0
=
So in the code above I want to substitute the call f( 3 ) fo= r

f( auto( x ) );

=C2=A0<= /div>

I think that in the preceding example= =C2=A0l=C2=A0

f( auto( 3 ) );

=
auto( 3 ) should not have any effect.

Or more= interesting example

#include <iostream>

void f( int &&x ) { std::cout << "= f( int &&( " << x << " ) )\n"; }
void= f( int &x ) { std::cout << "f( int &( " << x= << " ) )\n"; }

int main()
{=C2=A0=C2=A0=C2=A0 int x =3D 3;
=C2=A0=C2=A0=C2=A0 int y =3D 5;
=C2= =A0=C2=A0=C2=A0
=C2=A0=C2=A0=C2=A0 f( x < y ? x : y );
=C2=A0=C2= =A0=C2=A0 f( auto( x < y ? x : y ) );
}=C2=A0=C2=A0

=C2=A0=C2=A0
=C2=A0

--

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To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+unsubscribe@isocpp.org.
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