std:: tuple_size <std::tuple>
From cppreference.com
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Defined in header
<tuple>
|
||
|
template
<
class
...
Types
>
struct
tuple_size
<
std::
tuple
<
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
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operator std::size_t
|
converts the object to
std::
size_t
, returns
value
(public member function) |
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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
See also
| Structured binding (C++17) | binds the specified names to sub-objects or tuple elements of the initializer |
|
(C++11)
|
obtains the number of elements of a tuple-like type
(class template) |
|
(C++11)
|
obtains the size of a
pair
(class template specialization) |
|
(C++11)
|
obtains the size of an
array
(class template specialization) |
|
obtains the size of a
std::ranges::subrange
(class template specialization) |
|
|
(C++11)
|
tuple accesses specified element
(function template) |