std::tuple_size<std::tuple>

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Defined in header `<tuple>`

template< class T > class tuple_size; /undefined/	(1)	(since C++11)

template< class... Types > class tuple_size<tuple<Types...> > : public std::integral_constant<std::size_t, sizeof...(Types)> { };	(2)	(since C++11)

template< class T > class tuple_size<const T> : public std::integral_constant< typename std::remove_cv<decltype(std::tuple_size<T>::value)>::type, std::tuple_size<Tp>::value> { };	(3)	(since C++11)

template< class T > class tuple_size< volatile T > : public std::integral_constant< typename std::remove_cv<decltype(std::tuple_size<T>::value)>::type, std::tuple_size<Tp>::value> { };	(4)	(since C++11)

template< class T > class tuple_size< const volatile T > : public std::integral_constant< typename std::remove_cv<decltype(std::tuple_size<T>::value)>::type, std::tuple_size<Tp>::value> { };	(5)	(since C++11)

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

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)

Member types


Type	Definition

`value_type`	`std::size_t`

`type`	std::integral_constant<std::size_t, value>

[edit] Example

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

Output:

[edit] See also


std::tuple_size<std::array>	obtains the size of an `array` (class template specialization)

std::tuple_size<std::pair> (C++11)	obtains the size of a `pair` (class template specialization)

get	accesses specified element (function template)

tuple_element	obtains the type of the specified element (class template specialization)

std::tuple_size<std::tuple>

From Cppreference

Contents

Inherited from std::integral_constant

Member constants

Member functions

Member types

[edit] Example

[edit] See also