std::tuple_size<std::array>
Min standard notice:
Header: <array>
Provides access to the number of elements in an std::array as a compile-time constant expression.
# Declarations
template< class T, std::size_t N >
struct tuple_size< std::array<T, N> > :
std::integral_constant<std::size_t, N>
{ };
(since C++11)
# Example
#include <array>
int main()
{
auto arr = std::to_array("ABBA");
static_assert(std::tuple_size<decltype(arr)>{} == 5);
}