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Re: Templated Casting operators

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On 07/ 8/11 08:16 PM, Narinder wrote:
> On Jul 8, 8:42 am, Kai-Uwe Bux<jkherci...@gmx.net>  wrote:
>>
>> I think, gcc gets it right and lets you observe a language quirk: In this
>> version, the two conversion operators differ by constness. Thus, overload
>> resolution should be based on constness of the klass object being converted:
>>
>>    klass k; // declares a non-const klass object k
>>    show(k); // should choose the T&  version
>>    show( klass() ); // should choose the T const&  version because of 8.5.3/5
>>    double x1 = k; // should choose the non-const member as k is non-const
>>    double x2 = klass(); // should choose the non-const member as the
>>                         // temporary klass() is non-const
>>
>> The last issue is an inconsistency in the language: though klass() is non-
>> const, the temporary cannot be used to initialize a non-const reference.
>>
>> Best,
>>
>> Kai-Uwe Bux
>
> Hi
> Thanks for the reply.
>
> I was under the impress that a temporary variable would be cast only
> as a
> const&, which would make sense.
>
> I find the output of the following code :
>
> --------------------------------------------------------------
> #include<iostream>
> using namespace std;
>
> double pi = 3.142;
> struct klass
> {
>
>         template<class T>
>         operator T&()
>         {
>                 cout<<  "I am NON-const version\n";
>                 return pi;
>         }
>
>         template<class T>
>         operator const T&()
>         {
>                 cout<<  "I am CONST version\n";
>                 return pi;
>         }
> };
>
> int main()
> {
>
>         klass k;
>         double&x = k;
>         const double&const_x = k;
>
> }
>
> -------------------------------------------------------------
>
>
> more 'intuitivley' correct with msvc.
> I am NON-const version
> I am CONST version
>
>
> than gcc
> I am NON-const version
> I am NON-const version

I think gcc is correct because k is non-const.

With gcc 4.5.1, I get

I am NON-const version
I am CONST version

So there must have been a recent change.

-- 
Ian Collins

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Templated Casting operators Narinder <narinder.claire@gmail.com> - 2011-07-07 16:34 -0700
  Re: Templated Casting operators Alexander Bartolich <alexander.bartolich@gmx.at> - 2011-07-08 00:58 +0000
    Re: Templated Casting operators Narinder <narinder.claire@gmail.com> - 2011-07-07 22:36 -0700
      Re: Templated Casting operators Kai-Uwe Bux <jkherciueh@gmx.net> - 2011-07-08 09:42 +0200
        Re: Templated Casting operators Narinder <narinder.claire@gmail.com> - 2011-07-08 01:16 -0700
          Re: Templated Casting operators Ian Collins <ian-news@hotmail.com> - 2011-07-08 20:23 +1200
        Re: Templated Casting operators Narinder <narinder.claire@gmail.com> - 2011-07-08 01:37 -0700
          Re: Templated Casting operators Narinder <narinder.claire@gmail.com> - 2011-07-08 06:28 -0700
        Re: Templated Casting operators Narinder <narinder.claire@gmail.com> - 2011-07-08 01:40 -0700
          Re: Templated Casting operators Kai-Uwe Bux <jkherciueh@gmx.net> - 2011-07-09 00:06 +0200
            Re: Templated Casting operators Narinder <narinder.claire@gmail.com> - 2011-07-09 03:16 -0700
              Re: Templated Casting operators Kai-Uwe Bux <jkherciueh@gmx.net> - 2011-07-09 13:34 +0200
                Re: Templated Casting operators Narinder <narinder.claire@gmail.com> - 2011-07-09 07:18 -0700
                Re: Templated Casting operators Kai-Uwe Bux <jkherciueh@gmx.net> - 2011-07-10 01:15 +0200
                Re: Templated Casting operators Narinder <narinder.claire@gmail.com> - 2011-07-09 21:39 -0700
                Re: Templated Casting operators Narinder <narinder.claire@gmail.com> - 2011-07-09 22:01 -0700
                Re: Templated Casting operators Kai-Uwe Bux <jkherciueh@gmx.net> - 2011-07-10 13:43 +0200
                Re: Templated Casting operators Narinder <narinder.claire@gmail.com> - 2011-07-10 05:55 -0700
                Re: Templated Casting operators Narinder <narinder.claire@gmail.com> - 2011-07-10 00:19 -0700
                Re: Templated Casting operators Kai-Uwe Bux <jkherciueh@gmx.net> - 2011-07-10 12:03 +0200

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