Question

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Use templates to get an array’s size and end address

Can someone explain this template code that gives me the size of an array? (the first answer includes obtaining the value as a compile time constant)

How to get size of an array using metaprogramming? Multidimensional would be also appreciated.
So for example if I pass a type to this struct (how ever it’s called, let’s say get_dim) I would get:

get_dim<int>::value; //0
get_dim<int[1]>::value //1
get_dim<int[2][3]>::value //2,3

Answer 1

For one dimensional Arrays,

template<typename T, size_t N>
size_t size_of_array(T (&)[N])
{
   return N;
}

int arr[]={1,2,2,3,4,4,4,54,5};
cout << size_of_array(arr) << endl;     

A a[] = {A(),A(), A(), A(), A()};
cout << size_of_array(a) << endl;

Output:

9
5

Full Demo at Ideone : http://ideone.com/tpWk8

---

EDIT:

Another way (after seeing your edit),

template<typename T>
struct get_dim;

template<typename T, size_t N>
struct get_dim<T[N]>
{
    static const int value = N;
};

int main() 
{
       cout << get_dim<int[100]>::value;
       return 0;
}

Output:

100

http://ideone.com/wdFuz

---

EDIT:

For two dimensional arrays:

struct size2D
{
   size_t X;
   size_t Y;
};

template<typename T, size_t M, size_t N>
size2D size_of_array(T (&)[M][N])
{
   size2D s = { M, N};
   return s;
}
int arr[][5]={ {1,2,2,5,3}, {4,4,4,54,5}} ;
size2D size = size_of_array(arr);
cout << size.X <<", "<< size.Y << endl; 

Output:

2, 5

Code : http://ideone.com/2lrUq