std::is_rvalue_reference

Defined in header `<type_traits>`
template< class T > struct is_rvalue_reference;		(since C++11)

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

Template parameters

a type to check

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>`

Possible implementation

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

Example

#include <iostream>
#include <type_traits>
 
class A {};
 
int main() 
{
    std::cout << std::boolalpha;
    std::cout << std::is_rvalue_reference<A>::value << '\n';
    std::cout << std::is_rvalue_reference<A&>::value << '\n';
    std::cout << std::is_rvalue_reference<A&&>::value << '\n';
    std::cout << std::is_rvalue_reference<int>::value << '\n';
    std::cout << std::is_rvalue_reference<int&>::value << '\n';
    std::cout << std::is_rvalue_reference<int&&>::value << '\n';
}

Output:

false
false
true
false
false
true

is_lvalue_reference (C++11)	checks if a type is a lvalue reference (class template)
is_reference (C++11)	checks if a type is either a lvalue reference or rvalue reference (class template)