std::rank

From Cppreference

Defined in header `<type_traits>`

template< class T > struct rank;		(C++11 feature)

If T is an array type, provides the member constant value equal to the number of dimensions of the array. For any other type, value is 0.

Inherited from std::integral_constant

Member constants


`value`	the number of dimensions of `T` or zero (public static member constant)

Member functions


`operator std::size_t`	converts the object to std::size_t, returns `value` (public member function)

Member types


Type	Definition

`value_type`	`std::size_t`

`type`	std::integral_constant<std::size_t, value>

[edit] Equivalent definition

template<class T>
struct rank : std::integral_constant<std::size_t, 0> {};
 
template<class T>
struct rank<T[]> : public std::integral_constant<std::size_t, rank<T>::value + 1> {};
 
template<class T, size_t N>
struct rank<T[N]> : public std::integral_constant<std::size_t, rank<T>::value + 1> {};

[edit] Example

#include <iostream>
#include <type_traits>
 
int main()
{
    std::cout << std::rank<int[1][2][3]>::value << '\n';
    std::cout << std::rank<int[][2][3][4]>::value << '\n';
    std::cout << std::rank<int>::value << '\n';
}

Output:

3
4
0

[edit] See also

is_array (C++11)

checks if a type is an array type
(class template)

extent (C++11)

obtains the size of an array type along a specified dimension
(class template)

remove_extent (C++11)

removes one extent from the given array type
(class template)

remove_all_extents (C++11)

removes all extents from the given array type
(class template)