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Visual Studio 2012

Visual C++

C++ Language and Standard Libraries

Standard C++ Library

Header Files

<type_traits>

add_const Class

add_cv Class

add_pointer Class

add_reference Class

add_volatile Class

aligned_storage Class

alignment_of Class

common_type Class

conditional Class

decay Class

enable_if Class

extent Class

false_type Typedef

has_nothrow_assign Class

has_nothrow_constructor Class

has_nothrow_copy Class

has_nothrow_copy_constructor Class

has_nothrow_default_constructor Class

has_trivial_assign Class

has_trivial_constructor Class

has_trivial_copy Class

has_trivial_copy_constructor Class

has_trivial_default_constructor Class

has_trivial_destructor Class

has_virtual_destructor Class

integral_constant Class

is_abstract Class

is_arithmetic Class

is_base_of Class

is_compound Class

is_convertible Class

is_enum Class

is_floating_point Class

is_function Class

is_fundamental Class

is_integral Class

is_lvalue_reference Class

is_member_function_pointer Class

is_member_object_pointer Class

is_member_pointer Class

is_object Class

is_pod Class

is_pointer Class

is_polymorphic Class

is_reference Class

is_rvalue_reference Class

is_same Class

is_scalar Class

is_signed Class

is_standard_layout Class

is_unsigned Class

is_void Class

is_volatile Class

make_signed Class

make_unsigned Class

rank Class

remove_all_extents Class

remove_const Class

remove_cv Class

remove_extent Class

remove_pointer Class

remove_reference Class

remove_volatile Class

true_type Typedef

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is_union Class

Visual Studio 2012

Tests if type is a union.

template<class Ty>
    struct is_union;

Ty: The type to query.

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.

// std_tr1__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

Header: <type_traits>

Namespace: std

Reference

<type_traits>

is_class Class

Other Resources

<type_traits> Members

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