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std::is_union

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Revision as of 11:59, 14 May 2013 by P12 (Talk | contribs)

 
 
 
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is_union
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Template:ddcl list begin <tr class="t-dsc-header">

<td>
Defined in header <type_traits>
</td>

<td></td> <td></td> <tr class="t-dcl ">

<td >
template< class T >
struct is_union;
</td>

<td class="t-dcl-nopad"> </td> <td > (since C++11) </td> </tr> Template:ddcl list end

Checks whether T is an union type. Provides the member constant value which is equal to true, if T is an union type . Otherwise, value is equal to false.

Contents

Template parameters

T - a type to check

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)

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 class type (but not union type)
(class template) [edit]