| Defined in header <type_traits> | ||
|---|---|---|
template< class T > struct rank; | (since C++11) |
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 > constexpr std::size_t rank_v = rank<T>::value; | (since C++17) |
Inherited from std::integral_constant
Member constants
| value [static] | 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) |
| operator() (C++14) | returns value (public member function) |
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
#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
See also
| (C++11) | checks if a type is an array type (class template) |
| (C++11) | obtains the size of an array type along a specified dimension (class template) |
| (C++11) | removes one extent from the given array type (class template) |
| (C++11) | removes all extents from the given array type (class template) |
| std::experimental::rank_v
(library fundamentals TS) | variable template alias of std::rank::value (variable template) |
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