std::tuple_size<std::tuple>

Since C++11

Header: <tuple>

Provides access to the number of elements in a tuple as a compile-time constant expression.

# Declarations

template< class... Types >
struct tuple_size< std::tuple<Types...> >
: std::integral_constant<std::size_t, sizeof...(Types)> { };

(since C++11)

# Example

#include <iostream>
#include <tuple>
 
template <class T>
void test(T value)
{
    int a[std::tuple_size_v<T>]; // can be used at compile time
 
    std::cout << std::tuple_size<T>{} << ' ' // or at run time
              << sizeof a << ' '
              << sizeof value << '\n';
}
 
int main()
{
    test(std::make_tuple(1, 2, 3.14));
}

# See also