Re: [boost] [range] as_array broken

From: Eric Niebler (eric_at_[hidden])
Date: 2007-01-11 11:28:07

Thorsten Ottosen wrote:
> Eric Niebler wrote:
>> Thorsten Ottosen wrote:
> 
>>>> This is on HEAD, BTW.
>>> Fixed
>>
>> Thanks. You might want to add a test for this as well <nudge>.
> 
> Will don when I get some more time.

Thanks.

>> While we're at it, this trivial code fails to compile on msvc-7.1:
>>
>>    int rg[5] = {};
>>    boost::begin(rg);
>>
>> Clearly, it's a compiler bug. But the work-around is simple enough. In 
>> range/begin.hpp, the begin() overloads have the following signatures:
>>
>>    template< class T >
>>    typename range_iterator<T>::type begin( T& r )
>>
>>    template< class T >
>>    typename range_iterator<const T>::type begin( const T& r )
>>
>> If there were defined as follows:
>>
>>    template< class T >
>>    typename range_mutable_iterator<T>::type begin( T& r )
>>
>>    template< class T >
>>    typename range_const_iterator<T>::type begin( const T& r )
>>
>> .... the problem would go away, I think. Same is true for end(), size(), 
> 
> Hm ... I don't recall vc7.1 having any problems with this before. 
> AFAICT, it has to do with mpl:
> 
> ..\..\..\boost\range\iterator.hpp(33) : error C2039: 'type' : is not a 
> member of
>   'boost::mpl::eval_if_c<C,F1,F2>'
>          with
>          [
>              C=false,
>              F1=boost::range_const_iterator<boost::remove_const<wchar_t 
> [20]>::ty
> pe>,
>              F2=boost::range_mutable_iterator<wchar_t [20]>
>          ]

This is not an mpl-specific problem. As Shunsuke correctly observed, it 
has to do with your use of "T const" in the begin() function's return 
type, when T is deduced by msvc-7.1 as an array type. Please either try 
my suggestion above, or Shunsuke's (to use "add_const<T>::type" instead 
of "T const") to confirm that it does indeed fix the problem.

Thanks.

-- 
Eric Niebler
Boost Consulting
www.boost-consulting.com