std::rank (3) - Linux Manuals

std::rank: std::rank

NAME

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:

  0

  1
  2
  3