[boost] Discovering array size

From: AlisdairM (alisdair.meredith_at_[hidden])
Date: 2003-12-03 07:31:05

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();
}

AlisdairM