std::tuple_element() and std::tuple_size() in C++ with Examples

A tuple is an object that can hold a number of elements. The elements can be different data types. The elements of tuples are initialized as arguments in the order in which they will be accessed.

The functions-
tuple_element() and tuple_size()
are only defined for elements using tuple_like interface.

tuple_element():
The C++ function tuple_element(array) provides compile-type indexed access to the type of the elements of the array using a tuple-like interface.

Syntax-

template< size_t I, class T, size_t N >
struct tuple_element<I, array<T, N> >;

Parameters-

T − type for which the tuple element is obtained.
I − index of the element.
N − the size of the array.

Example-
Below is the C++ program to implement the concept of tuple_element(array)-

C++

// C++ program to implement
// the above approach

#include <array>
#include <iostream>
#include <tuple>
#include <type_traits>
using namespace std;

// Driver code
int main()
{
    // Define array
    array<int, 3> data{ 3, 5, 10 };

    // Type of element at index 0
    using type = std::tuple_element<0,
                                    decltype(data)>::type;

    // Compare type with int
    // returns true
    cout << std::is_same<type,
                         int>::value
         << '\n';

    // Compare type with char
    // returns false
    cout << std::is_same<type,
                         char>::value
         << '\n';
}

Output

1
0

tuple_size():
The C++ function tuple_size(array) returns the total number of elements present in the array.

Syntax-

template< class T, size_t N >
class tuple_size< array<T, N> > :
 integral_constant<size_t, N>
{ };

Parameters-

T − type for which the tuple size is obtained.

Example-
Below is the C++ program to implement the concept of tuple_size()-

C++

// C++ program to implement
// the above approach
#include <array>
#include <iostream>
using namespace std;

// Driver code
int main()
{
    // Array of size 6
    array<int, 6> a;

    // Find size using tuple_size
    cout << tuple_size<decltype(a)>::value;
    return 0;
}

Output

6