Std::rank (3) Linux Manual Page

std::rank – std::rank

Synopsis

Defined in header<type_traits>

    template <class T>
    (since C++ 11)

        struct rank;

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.
Helper variable template

template< class T >                                    (since C++17)

inline constexpr std::size_t rank_v = rank<T>::value;

Inherited from std::integral_constant

Member constants

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

Member functions

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

operator() returns value
(public member function)
(C++14)

Member types

Type Definition
value_type std::size_t
type std::integral_constant<std::size_t, value>

Possible implementation

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

Example

// Run this code

#include <iostream>

#include <type_traits>
int main()

{
    std::cout << std::rank<int>{} << "\n\n";
    std::cout << std::rank<int[5]>{} << '\n';
    std::cout << std::rank<int[5][5]>{} << '\n';
    std::cout << std::rank<int[][5][5]>{} << '\n';
}

Output:

  1
  2
  3

std::rank (3) Linux Manual Page