Re: [boost] Discovering array size

From: Pavol Droba (droba_at_[hidden])
Date: 2003-12-03 08:00:46

On Wed, Dec 03, 2003 at 12:31:05PM +0000, AlisdairM wrote:
> The following seems such an obvious utility, I was surprised I could not 
> find it in the boost distribution.  Could someone point me to the 
> equivalent if I am missing it.  Alternatively, is this worth cleaning up 
> for a submission?
> 
> Basic problem is to know the size of the following array:
> 
> int[] aInts = { 1, 2, 3 );
> 
> 
> The implementation is simple enough:
> 
> 
> template< class T, std::size_t N >
> std::size_t size( const T (&)[N] )
> {
>     return N;
> }
> 
> assert( size(aInts) == 3 );
> 
> 
> We can also overload for boost::array.
> 
> 
> I suspect there may be a way to make this a compile-time constant, but 
> can't figure out the automatic type deduction yet.
> 
> If runtime is preferred, then adding an overload for classes with the size 
> member function allows standard containers to work as well.
> 
> 
> template< class T, std::size_t N>
> inline std::size_t size( const boost::array<T, N> & )
> {
>     return  N;
> }
> 
> template< class T >
> inline std::size_t size( const T &t )
> {
>     return  t.size();
> }
> 

Such a functionality is present in container_traits. Check the implementation in the sandbox. 
string_algo implementation contains also some workarounds for broken compilers.

Regards,

Pavol