std::is_union (3) - Linux Man Pages

std::is_union: std::is_union

NAME

std::is_union - std::is_union

Synopsis


Defined in header <type_traits>
template< class T > (since C++11)
struct is_union;


Checks whether T is a union type. Provides the member constant value, which is equal to true if T is a union type . Otherwise, value is equal to false.

Template parameters


T - a type to check


Helper variable template


template< class T > (since C++17)
inline constexpr bool is_union_v = is_union<T>::value;


Inherited from std::integral_constant

Member constants


value true if T is a union type , false otherwise
         (public static member constant)
[static]

Member functions


              converts the object to bool, returns value
operator bool (public member function)


operator() returns value
              (public member function)
(C++14)

Member types


Type Definition
value_type bool
type std::integral_constant<bool, value>

Example


// Run this code


  #include <iostream>
  #include <type_traits>


  struct A {};


  typedef union {
      int a;
      float b;
  } B;


  struct C {
      B d;
  };


  int main()
  {
      std::cout << std::boolalpha;
      std::cout << std::is_union<A>::value << '\n';
      std::cout << std::is_union<B>::value << '\n';
      std::cout << std::is_union<C>::value << '\n';
      std::cout << std::is_union<int>::value << '\n';
  }

Output:


  false
  true
  false
  false

See also


is_class checks if a type is a non-union class type
         (class template)
(C++11)