tuple_element Class <utility>
The latest version of this topic can be found at Visual Studio 2017 Documentation.
Wraps the type of a pair element.
Syntax
// CLASS tuple_element (find element by index)
template <size_t Index, class Tuple>
struct tuple_element;
// struct to determine type of element 0 in pair
template <class Ty1, class Ty2>
struct tuple_element<0, pair<Ty1, Ty2>>;
// struct to determine type of element 1 in pair
template <class Ty1, class Ty2>
struct tuple_element<1, pair<Ty1, Ty2>>;
// tuple_element for const
template <size_t Index, class Tuple>
struct tuple_element<Index, const Tuple>;
// tuple_element for volatile
template <size_t Index, class Tuple>
struct tuple_element<Index, volatile Tuple>;
// tuple_element for const volatile
template <size_t Index, class Tuple>
struct tuple_element<Index, const volatile Tuple>;
template <size_t Index, class Tuple>
using tuple_element_t = typename tuple_element<Index, Tuple>::type;
Parameters
Index
The position of the element; for pair this value is either 0 or 1.
T1
The type of the first pair element.
T2
The type of the second pair element.
type
Remarks
The templates are specializations of the template class tuple_element Class. Each has a single member typedef, type, which is a synonym for the type of the element at the specified position in the pair, with any const and/or volatile qualifications preserved. tuple_element_t is a convenient alias for tuple_element<N, pair<T1, T2>>::type. Use the get Function <utility> to return the element at a specified position or (in C++14 / Visual Studio 2015) of a specified type.
Example
#include <utility>
#include <iostream>
using namespace std;
typedef pair<int, double> MyPair;
int main()
{
MyPair c0(0, 1.333);
// display contents " 0 1"
cout << " " << get<0>(c0);
cout << " " << get<1>(c0) << endl;
// display first element " 0" by index
tuple_element<0, MyPair>::type val = get<0>(c0);
cout << " " << val;
// display second element by type
tuple_element<1, MyPair>::type val2 = get<double>(c0);
cout << " " << val2 << endl;
}
/*
Output:
0 1.333
0 1.333
*/
Requirements
Header: <utility>
Namespace: std