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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.

// 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

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.

#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  
*/  

Header: <utility>

Namespace: std

<utility>
get Function <utility>
tuple_size Class

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