< cpp‎ | utility‎ | tuple
Utilities library
Language support
Type support (basic types, RTTI)
Library feature-test macros (C++20)
Dynamic memory management
Program utilities
Coroutine support (C++20)
Variadic functions
Debugging support
Three-way comparison
General utilities
Date and time
Function objects
Formatting library (C++20)
Relational operators (deprecated in C++20)
Integer comparison functions
Swap and type operations
Common vocabulary types
Elementary string conversions

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.


[edit] Helper variable template

template< class T >
inline constexpr std::size_t tuple_size_v = tuple_size<T>::value;
(since C++17)

Inherited from std::integral_constant

Member constants

(public static member constant)

Member functions

operator std::size_t
converts the object to std::size_t, returns value
(public member function)
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 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

[edit] See also

Structured binding (C++17) binds the specified names to sub-objects or tuple elements of the initializer[edit]
obtains the number of elements of a tuple-like type
(class template) [edit]
obtains the size of a pair
(class template specialization) [edit]
obtains the size of an array
(class template specialization) [edit]
obtains the number of components of a std::ranges::subrange
(class template specialization) [edit]
tuple accesses specified element
(function template) [edit]