Re: [boost] [PQS] Resizable vectors/matrices

From: Bronek Kozicki (brok_at_[hidden])
Date: 2006-06-18 07:49:00

Janek Kozicki wrote:
>> BTW, this is where I'd really like to see templatized
>> typedefs in C++, allowing us to define:
>>
>>     template< int N, type T >
>>     typedef vector< N, T, false > fixed_vector;
>>
>>     template< int N, type T >
>>     typedef vector< N, T, true > resizable_vector;
>>
>> Thus we'd have:
>>
>>     fixed_vector<N,T>
>>     resizable_vector<N,T>
>>
>> while using the common vector template defined above.
> 
> 
> uh, wait. It's not possible currently? I'm not 100% sure but I think
> that I was using similar code some time in the past...

I think not. You probably meant feature described in 
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2003/n1489.pdf , but it's 
not in the C++0x draft, yet. There is simple way to emulate this, 
unfortunatelly with different semantics that would make metaprograms much more 
difficult to write:
   template< int N, type T >
   struct  resizable_vector : vector< N, T, true > {};

The difficulty comes from the fact that:
   some_useful_template<vector<10, int, true> >
and:
   some_useful_template<resizable_vector<10, int> >

are two distinct types

B.