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std::is_rvalue_reference

From cppreference.com
< cpp‎ | types
 
 
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is_rvalue_reference
(C++11)
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Compile-time rational arithmetic
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Defined in header <type_traits>
template< class T >
struct is_rvalue_reference;
(since C++11)

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

The behavior of a program that adds specializations for is_rvalue_reference or is_rvalue_reference_v (since C++17) is undefined.

Contents

[edit] Template parameters

T - a type to check

[edit] Helper variable template

template< class T >
inline constexpr bool is_rvalue_reference_v = is_rvalue_reference<T>::value;
(since C++17)

Inherited from std::integral_constant

Member constants

value
[static]
true if T is an rvalue reference type , false otherwise
(public static member constant)

Member functions

operator bool
converts the object to bool, returns value
(public member function)
operator()
(C++14)
returns value
(public member function)

Member types

Type Definition
value_type bool
type std::integral_constant<bool, value>

[edit] Possible implementation

template <class T> struct is_rvalue_reference      : std::false_type {};
template <class T> struct is_rvalue_reference<T&&> : std::true_type {};

[edit] Example

#include <type_traits>
 
class A {};
 
int main()
{
    static_assert( not std::is_rvalue_reference_v<A> );
    static_assert( not std::is_rvalue_reference_v<A&> );
    static_assert(     std::is_rvalue_reference_v<A&&> );
    static_assert( not std::is_rvalue_reference_v<int> );
    static_assert( not std::is_rvalue_reference_v<int&> );
    static_assert(     std::is_rvalue_reference_v<int&&> );
}

[edit] See also

checks if a type is a lvalue reference
(class template) [edit]
checks if a type is either a lvalue reference or rvalue reference
(class template) [edit]