std::is_union
Defined in header <type_traits>
|
||
template< class T > struct is_union; |
(since C++11) | |
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 > inline constexpr bool is_union_v = is_union<T>::value; |
(since C++17) | |
Inherited from std::integral_constant
Member constants
value [static] |
true if T is a union type , false otherwise (public static member constant) |
Member functions
operator bool |
converts the object to bool, returns value (public member function) |
operator() (C++14) |
returns value (public member function) |
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
(C++11) |
checks if a type is a non-union class type (class template) |