std::tuple_element<std::array>

 

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tuple_element

Deduction guides(C++17)

 

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

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

See also

tuple_element	obtains the type of the specified element (class template specialization)
std::tuple_element<std::pair> (C++11)	obtains the type of the elements of pair (class template specialization)