Re: [boost] Typeof registration of partially specialized templates

From: Tobias Schwinger (tschwinger_at_[hidden])
Date: 2006-01-27 11:07:28

Arkadiy Vertleyb wrote:
> "Tobias Schwinger" <tschwinger_at_[hidden]> wrote
> 
> 
>>That's not exactly what I meant. It's possible to
>>
>>   #define REG_SPEC(a,b) \
>>      ... struct my_traits< a_private_return_type b > { ... }
> 
> 
> Do you mean:
>     ... struct my_traits< a_private_return_type(b) > { ... }
> ?
> 

No, the original should be OK because input for 'b' must be parenthesized to allow any number of commas. For the expansion it means

   ... struct my_traits< a_private_return_type (b-without-parentheses) > ...
 
, though.

>>And then use "my_traits< a_private_return_type(T) >".
>>However, we can't apply this technique globally because not all types are
>>valid function parameter types 
> 
> Which types are not valid?  void?
> 

Well, is this code legal?

    #include <boost/mpl/assert.hpp>
    #include <boost/type_traits/is_same.hpp>

    template<typename R,typename T> struct func1
    {
      typedef R type(T);
    };

    BOOST_MPL_ASSERT(( boost::is_same< func1<void,void>::type, void() > ));

MSVC thinks it is but GCC and Comeau disagree -- I'm not sure which one is right (according to 8.3.5-9). Fact is, it means trouble in practice. Completely illegal would be cv-void.

> [... experiments with line breaking options of news clients]
> 
> I don't have such option.  Trying maximum (132).
> 

Me not either - just entered 0 ;-) (Thunderbird).

Regards,

Tobias