std::tuple_size<std::tuple>
From cppreference.com
| Defined in header <tuple>
|
||
template< class... Types >
struct tuple_size< std::tuple<Types...> >
: std::integral_constant<std::size_t, sizeof...(Types)> { };
|
(since C++11) | |
Provides access to the number of elements in a tuple as a compile-time constant expression.
Helper variable template
template< class T >
constexpr std::size_t tuple_size_v = tuple_size<T>::value;
|
(since C++17) | |
Inherited from std::integral_constant
Member constants
value [static] |
sizeof...(Types) (public static member constant) |
Member functions
operator std::size_t |
converts the object to std::size_t, returns value (public member function) |
operator() (C++14) |
returns value (public member function) |
Member types
| Type | Definition |
value_type
|
std::size_t
|
type
|
std::integral_constant<std::size_t, value>
|
Example
Run this code
#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));
}
Possible output:
3 12 16