std::is_union – cppreference.com

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definiert in Header `<type_traits>`

`template< class T > struct is_union;`		(seit C++11)

Wenn T a union-Typ ist, stellt das Mitglied konstanten value gleich true. Für jede andere Art, value ist false .

Original:

If T is a union type, provides the member constant value equal true. For any other type, value is false.

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Inherited from std::integral_constant

Member constants


	`true` wenn `T` is a union type , `false` anders Original: `true` if `T` is a union type , `false` otherwise The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (public static Mitglied konstanten)

Member functions


	wandelt das Objekt `bool`, gibt `value` Original: converts the object to `bool`, returns `value` The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (öffentliche Elementfunktion)

Member types


Type Original: Type The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.	Definition

`value_type`	`bool`

`type`	`std::integral_constant<bool, value>`

Beispiel

#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:

Siehe auch


	checks if a type is a class type (but not union type) (Klassen-Template) [edit]