std::is_union
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Cpp/docs/latest/types/is union
std::is_union
Defined in header <type_traits>
|
||
---|---|---|
|
(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
|
(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
#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) |
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