is-union-class.md

description	title	ms.date	f1_keywords	helpviewer_keywords	ms.assetid
Learn more about: is_union Class	is_union Class	11/04/2016	type_traits/std::is_union	is_union class is_union	80eda256-40b8-4db5-9ac1-d58bb8032a3e

is_union Class

Tests if type is a union.

Syntax

template <class Ty>
struct is_union;

Parameters

Ty
The type to query.

Remarks

An instance of the type predicate holds true if the type Ty is a union type or a cv-qualified form of a union type, otherwise it holds false.

Example

// std__type_traits__is_union.cpp
// compile with: /EHsc
#include <type_traits>
#include <iostream>

struct trivial
    {
    int val;
    };

union ints
    {
    int in;
    long lo;
    };

int main()
    {
    std::cout << "is_union<trivial> == " << std::boolalpha
        << std::is_union<trivial>::value << std::endl;
    std::cout << "is_union<int> == " << std::boolalpha
        << std::is_union<int>::value << std::endl;
    std::cout << "is_union<ints> == " << std::boolalpha
        << std::is_union<ints>::value << std::endl;

    return (0);
    }

is_union<trivial> == false
is_union<int> == false
is_union<ints> == true

Requirements

Header: <type_traits>

Namespace: std

See also

<type_traits>
is_class Class