tuple_size Class <tuple>

2018-01-02

The latest version of this topic can be found at tuple_size Class;.

Reports the number of elements that a tuple contains.

Syntax

// TEMPLATE STRUCT tuple_size  
template <class Tuple>  
struct tuple_size;  
 
// size of tuple  
template <class... Types>  
struct tuple_size<tuple<Types...>>  
: integral_constant<size_t, sizeof...(Types)>;  
 
// size of const tuple  
template <class Tuple>  
struct tuple_size<const Tuple>;  
 
// size of volatile tuple  
template <class Tuple>  
struct tuple_size<volatile Tuple>;  
 
// size of const volatile tuple  
template <class Tuple>  
struct tuple_size<const volatile Tuple>;

Parameters

Tuple
The type of the tuple.

Remarks

The template class has a member value that is an integral constant expression whose value is the extent of the tuple type Tuple.

Example

#include <tuple>   
#include <iostream>  
  
using namespace std;  
  
typedef tuple<int, double, int, double> MyTuple;  
int main()  
{  
    MyTuple c0(0, 1.5, 2, 3.7);  
  
    // display contents " 0 1 2 3"   
    cout << " " << get<0>(c0);  
    cout << " " << get<1>(c0);  
    cout << " " << get<2>(c0);  
    cout << " " << get<3>(c0) << endl;  
  
    // display size " 4"   
    cout << " " << tuple_size<MyTuple>::value << endl;  
}  
  
/*  
Output:  
0 1.5 2 3.7  
4  
*/

Requirements

Header: <tuple>

Namespace: std

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