std::tuple_element<std::array> (3) - Linux Manuals

std::tuple_element<std::array>: std::tuple_element<std::array>

NAME

std::tuple_element<std::array> - std::tuple_element<std::array>

Synopsis

Defined in header <array>
template< std::size_t I, class T, std::size_t N > (since C++11)
struct tuple_element<I, array<T, N> >;

Provides compile-time indexed access to the type of the elements of the array using tuple-like interface

Member types

Member type Definition
type the type of elements of the array

Possible implementation

  template<std::size_t I, class T>
    struct tuple_element;

  template<std::size_t I, class T, std::size_t N>
    struct tuple_element<I, std::array<T,N> >
    {
       using type = T;
    };

Example

// Run this code

  #include <array>
  #include <iostream>
  #include <tuple>
  #include <type_traits>

  int main()
  {
     // define compile time constant array and get the type of the element at position 0
     std::array<int, 10> data {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
     using T = std::tuple_element<0, decltype(data)>::type; // int

     std::cout << std::boolalpha;
     std::cout << std::is_same<T, int>::value << '\n';

     const auto const_data = data;
     using CT = std::tuple_element<0, decltype(const_data)>::type; // const int

     // the result of tuple_element depends on the cv-qualification of the tuple-like type
     std::cout << std::is_same<T, CT>::value << '\n';
     std::cout << std::is_same<CT, const int>::value << '\n';
  }

Output:

  true
  false
  true