template <typename T, std::size_t...>
constexpr auto object_count(T& t)
{
	return 1u;
}

template <std::size_t ... Ns, typename T, std::size_t n>
constexpr auto object_count(T (&arr)[n] )
{
	return n * object_count(arr[0]);
}

   // eg, with
    double d;
    double a1[5];
    double a2[5][3];
    double a3[5][4][2];

    // then
    static_assert(object_count(d)==1,"?");
    static_assert(object_count(a1)==5,"?");
    static_assert(object_count(a2)==15,"?");
    static_assert(object_count(d3)==40,"?);

     // some type T
     T d3[3][2][5];

      sizeof(d3)/sizeof(T)