table of contents
std::is_union(3) | C++ Standard Libary | std::is_union(3) |
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.
The behavior of a program that adds specializations for is_union
or is_union_v
(since C++17) is undefined.
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
[static] (public static member constant)
Member functions¶
operator bool converts the object to bool, returns value
(public member function)
operator() returns value
(C++14) (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¶
is_class checks if a type is a non-union class type
(C++11) (class template)
2022.07.31 | http://cppreference.com |