220 23397 <4a61195c-a3b8-446f-9d36-5dcc7287c24a@isocpp.org> article Path: news.gmane.org!not-for-mail From: Dejan Milosavljevic Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Dynamic/Temporal constatization Date: Sat, 2 Jan 2016 06:08:25 -0800 (PST) Lines: 356 Approved: news@gmane.org Message-ID: <4a61195c-a3b8-446f-9d36-5dcc7287c24a@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_0_1484563950.1451743705442" X-Trace: ger.gmane.org 1451743711 22729 80.91.229.3 (2 Jan 2016 14:08:31 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sat, 2 Jan 2016 14:08:31 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBDFYFDOFWUGBBWVTT62AKGQEPEXAGCY@isocpp.org Sat Jan 02 15:08:30 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ob0-f200.google.com ([209.85.214.200]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1aFMr7-0005xE-5C for gclcip-std-proposals@m.gmane.org; Sat, 02 Jan 2016 15:08:29 +0100 Original-Received: by mail-ob0-f200.google.com with SMTP id or18sf632750816obb.2 for ; Sat, 02 Jan 2016 06:08:28 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:message-id: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=FwxYngvF1me95fkCoU5m/5NzbZ+ELVX3yu1y8+O7Nro=; b=eaQCLEPIYxnqEMOb2qLVQ8brhAbK7mBJWZC9BFGEuTSphVYxu6+5ZxOjZuUL9r99dn 9M9J1ugGTS8uMOcKk1gF6TyQ5jWVCd3rkaWb0JcYXnLfjn4EbMDp1UXEMhHjajfMVOV0 6obID5rnufUJBj0AikjP7SC+y0GKALA3wlvFo/OPOYkPMB8L8Q8qWkniMvvbLavfN2Dh f/0MtY9PfXjau2EFq12EmQFQwyCs5oRYXBQCevrrgmZQaPzXEHL7Exa4DUVCI4YzqRaw TMfodF1Y/DGEz7amyR1z6IgISCxdMYkbibqFNw8CHOWcNgD80AqYIlq5Z8YvYpat960Y aCww== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=date:from:to:message-id: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=FwxYngvF1me95fkCoU5m/5NzbZ+ELVX3yu1y8+O7Nro=; b=V47bsGYVZKeFzh6+BF6Ar7EmvwWBORrtI4e2KCmv1yuYVIFiQwKSB1KdpBQoMrldt4 38O/PF1mWebI3J37v49zdvdgPYxOU4TT4SynpXwHlWLPpsHL4BqRu2vMbr/6nE3Bhjxp y4l4DcwQOtVAMAv1gVqfdUdQ8OqYxxY51x3dAKNjFtzwWgXoU9hTziNGSIyC5039tjub Mal7QdX9yJNmsoeBYYEx9yWP7zUkkxfS4Y21bvzo4FduOYbOayd6bHohuKeZlCBBLSs6 6eNq/L5GxDNIc1W5yUM8YeFzjvSOu1VKoCXKXAuDuFIb0myfbODetpIZsvjysX14PZ3S 4tLQ== 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: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=FwxYngvF1me95fkCoU5m/5NzbZ+ELVX3yu1y8+O7Nro=; b=C37qrZxWbb6wVVXi8YJ/hw6H/iqH55k7md3aNaTEDjJiBe5CLJnSKrl/xoCiUYB1Yc T5PIse8N4CrfhGGwLlUnR12Vu/pTsLf5oYhLJIv0QjuBxzKCJTJC/WYh+7xeArzmliQT YvkWqXCinCOyRGtaNcEayiOK3MyVNf4ojlGA4lEW0mvE9ddSutDUibhtqPbBachCMSIk mXkEW1osEBaMia86tZ31HskkfodxlOVYMqWAfMzHiOcjRaljTDHHyzBcx04Hj4YS6abb K3u4aL2HDh/AZL9wvAH+XA3EGFAh3cvc+ueCunb7qgbeorfk9BCfvBaoSn/s5l3rrTfr 12MA== X-Gm-Message-State: ALoCoQnkEAjDj43na1gL/4+lAyQAApWZjS1fp5RFGGMJjo8Zi0XjLZHhNrQNvPt26qAtNIWEhKcZ6U6dLKPMVY8nGKBXWgg66A== X-Received: by 10.182.96.136 with SMTP id ds8mr22465553obb.17.1451743707932; Sat, 02 Jan 2016 06:08:27 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.18.137 with SMTP id 9ls2953918ios.106.gmail; Sat, 02 Jan 2016 06:08:26 -0800 (PST) X-Received: by 10.50.57.100 with SMTP id h4mr1173568igq.6.1451743706380; Sat, 02 Jan 2016 06:08:26 -0800 (PST) X-Original-Sender: dmilos@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:23397 Archived-At: ------=_Part_0_1484563950.1451743705442 Content-Type: multipart/alternative; boundary="----=_Part_1_1827313706.1451743705447" ------=_Part_1_1827313706.1451743705447 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable =20 Hi Idea is simple. Make instance temporally constant. =20 Small example: Container c;=20 func( *const*( c ) );=20 *const*( c ).f(); =20 =20 And in details: =20 =20 Table of Contents. - I. Abstract - II. Motivation - III. Solution - IV. Syntax - V. Summary - VI. Impact On the Standard =20 I. Abstract Dynamic constatization of instances.=20 II. Motivation Problem 1:[*Example*:=20 template< typename T> class Container{ public: typedef T* iterator; typedef T const* const_iterator; iterator begin(); const_iterator begin()const; iterator end(); const_iterator end()const; void f(); void f()const; }; Container cont; for( auto const & iter : cont ){ // in here we want to be called *begin()= const* and *end()const* } =E2=80=94*end example*] =20 Problem 2: [*Example*:=20 void func( Container & c ); void func( Container const & c ); void do_something(){ Container cont; func(cont); // In here we want to call func( Container const& c ); } =E2=80=94*end example*]=20 =20 III. Solution Solutions within current standard=20 =20 - Bloat code with new functions that has different name which will serve= =20 to only to only one purpose. Examples are: vector::cbegin and vector::cend, vector::crbegin,=20 vector::crend.=20 - Use helper variable with const qualifier. =20 [*Example*:=20 =20 { Container const& ccont =3D cont; for( auto & iter : cont ){ } } =20 =E2=80=94*end example*]=20 - Use some of existing cast operator which will directly lead to=20 misunderstanding and possible to something more serious.=20 [*Example*:=20 =20 // Some companies might forbid usage of reinterpret_cast for( auto const & iter : reinterpret_cast< Container const& >( co= nt ) ){ // ... ... ... } =20 for( auto const & iter : static_cast< Container const& >( cont ) = ){ // ... ... ... } // it is expected that const_cast remove constness not to add for( auto const & iter : const_cast< Container const& >( cont ) )= { // ... ... ... } =20 for( auto const & iter : ( Container const& )( cont ) ){ // ... ... ... } =20 =20 =E2=80=94*end example*] =20 In all cases code become less readable if we have type with realy long= =20 name e.g. std::map< std::string, std::pair< std::string, std::string > >= ..=20 =20 =20 By adding ability to const to act on instances.On range loop: [*Example*:=20 Container cont; for( auto &iter : const( cont ) ){ // ... } =E2=80=94*end example*]=20 =20 On instance: [*Example*:=20 Container cont; func( const( cont ) ); const( cont ).f(); =E2=80=94*end example*]=20 =20 On pointers: [*Example*:=20 Container cont; Container * cp1 =3D &cont; const( cp1 )->f(); Container *const cp2 =3D &cont; const( cp2 )->f(); Container const* cp3 =3D &cont; const( cp3 )->f(); =E2=80=94*end example*]=20 IV. Syntax*const-operator:*const ( *expression* ) V. Summary - Avoid code bloat by adding functions which to allow explicit call of= =20 const functions. - Avoid misusing of cast operators to add temporal constness. - Avoid using of temporal const references. VI. Impact On the Standard Core No effect. No new keywords.=20 No new tokens.=20 No changes to old syntax.=20 Pure extension.=20 Backward compatible.=20 Library No effect. Existing code. No effect. --=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. Visit this group at https://groups.google.com/a/isocpp.org/group/std-propos= als/. ------=_Part_1_1827313706.1451743705447 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
=C2=A0

Hi

Idea is simple. M= ake instance temporally constant.
=C2= =A0
Small example:
=C2=A0=C2=A0=C2=A0 Container<int> c;=C2=A0
=C2=A0= =C2=A0=C2=A0 func( const( c ) );=C2=A0
=C2=A0=C2=A0=C2= =A0 const( c ).f();
=C2=A0
=C2=A0
And in details:
=C2=A0=C2=A0
=C2=A0
= Table of Contents.
  • I. Abstract=
  • II. Motivation
  • III. Solution
  • IV. Synta= x
  • V. Summary
  • VI. Impact On the Standard
I. Abstract
Dynamic constatization of i= nstances.
II. Motivation
=
Problem 1:
[Example: 
template< typename T>
 class Container{
   public:
     typedef T* iterator;
     typedef T const* const_iterator;
     iterator begin();
     const_iterator begin()const;
     iterator end();
     const_iterator end()const;
     void f();
     void f()const;
  };

  Container<int> cont;

  for( auto const & iter : cont ){ // in here we want to be called b=
egin()const and end()const
  }
=E2=80=94end example]
=C2=A0
Problem 2:
[Ex= ample: 
   void func( Container<int>=
 & c );
   void func( Container<int> const & c );

   void do_something(){
    Container<int> cont;

    func(cont); // In here we want to call func( Container<int> const=
& c );
   }
=E2=80=94end example= ]
=C2=A0
<= p class=3D"NovaStranica">

III. Solu= tion
Solutions within current sta= ndard
  • Bloat code with new functions that has different nam= e which will serve to only to only one purpose.
    Examples ar= e: vector::cbegin and vector::cend, vector:= :crbegin, vector::crend.
  • Use hel= per variable with const qualifier.
    =C2=A0
    [Ex= ample: 
      {
   Container<int> const& ccont =3D cont;
   for( auto & iter : cont ){
   }
  }
    =E2=80=94end example] =
  • Use some of existing cast operator which will= directly lead to misunderstanding and possible to something more serious. =
    [Example: 
      //=
 Some companies might forbid usage of reinterpret_cast
  for( auto const & iter : reinterpret_cast< Container<int> co=
nst& >( cont ) ){
    // ... ... ...
  }

  for( auto const & iter : static_cast< Container<int> const&a=
mp; >( cont ) ){
    // ... ... ...
  }
  // it is expected that const_cast remove constness not to add
  for( auto const & iter : const_cast< Container<int> const&am=
p; >( cont ) ){
    // ... ... ...
  }

  for( auto const & iter : ( Container<int> const& )( cont ) =
){
      // ... ... ...
  }
 =20
    =E2=80=94end example]=C2=A0
In all cases co= de become less readable if we have type with realy long name e.g. std::map< std::string, std::pair< std::string, std::string > &= gt;.
By adding ability to const to act on= instances.
On range loop:
[Example:
= 
Container<int> cont;
for( auto &iter : const( cont ) ){
 // ...
 }
=E2=80=94<= i>end example]
=C2=A0
On instance:
[Examp= le: 
Container<int>=
; cont;

func( const( cont ) );

const( cont ).f();
=E2=80=94<= i>end example]
=C2=A0
On pointers:
[Examp= le: 
Container<int>=
; cont;

Container<int> * cp1 =3D &cont;
const( cp1 )->f();
Container<int> *const cp2 =3D &cont;
const( cp2 )->f();
Container<int> const* cp3 =3D &cont;
const( cp3 )->f();
=E2=80=94<= i>end example]

IV. Syntax
const-operator:
const ( expression )

V. Summary
    Avoid code bloat by adding functions which to allow explicit call of const functions.
  • Avoid misusing of cast operators to add t= emporal constness.
  • Avoid using of temporal const= references.
= VI. Impact On the Standard
= =C2=A0 Core
=C2=A0=C2=A0=C2=A0 No effect.
=C2=A0=C2=A0=C2= =A0 No new keywords.
=C2=A0=C2=A0=C2=A0 No new tokens.=
=C2=A0=C2=A0=C2=A0 No changes to old syntax.
=C2=A0=C2=A0=C2=A0 Pure extension.
=C2=A0= =C2=A0=C2=A0 Backward compatible.
=C2=A0 Library
=C2=A0=C2=A0=C2=A0 No effect.
<= div class=3D"NaslovPod ">=C2=A0 Existing code.
=C2=A0=C2=A0= =C2=A0 No effect.

--

---
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.
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