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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) http://cppreference.com 2022.07.31 std::is_union(3)
NAME | Synopsis | Template parameters | Member constants | Member functions | Member types | Example | Output: | See also
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