std::tuple_sizestd::tuple - cppreference.com (original) (raw)

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

Contents

• 1 Helper variable template
• 2 Inherited from std::integral_constant
  • 2.1 Member constants
  • 2.2 Member functions
  • 2.3 Member types
  • 2.4 Example
  • 2.5 See also

[edit] 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

| | sizeof...(Types) (public static member constant) | | --------------------------------------------------- |

Member functions

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

Member types

[edit] Example

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

Possible output:

[edit] See also