std::is_rvalue_reference

From cppreference.com
< cpp‎ | types
 
C++
 
Utilities library
Type support (basic types, RTTI, type traits)
Dynamic memory management
Error handling
Program utilities
Variadic functions
Library feature-test macros
Date and time
Function objects
(C++11)
(C++11)
(C++14)
Relational operators (deprecated in C++20)
Comparisons (C++20)
Common vocabulary types
(C++11)
(C++17)
(C++17)
(C++17)
(C++17)
(C++17)

Swap, forward and move
(C++14)
(C++11)
(C++11)
(C++11)
Elementary string conversions
(C++17)
(C++17)
(C++17)
Type operations
(C++11)
(C++17)
(C++17)
 
Type support
Basic types
Fundamental types
Fixed width integer types (C++11)
Numeric limits
C numeric limits interface
Runtime type information
Type traits
Type categories
(C++11)
(C++14)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
is_rvalue_reference
(C++11)
(C++11)
(C++11)
(C++11)
Type properties
(C++11)
(C++11)
(C++11)
(C++11)
(C++14)
(C++11)
(C++17)
(C++11)
(C++11)
(C++11)
(C++11)(until C++20)
(C++11)(deprecated in C++20)
(C++11)
(C++11)
(C++20)
(C++20)
(C++17)
Type trait constants
(C++11)(C++17)(C++11)(C++11)
Metafunctions
(C++17)
(C++17)
(C++17)
Endian
(C++20)
Constant evaluation context
(C++20)
Supported operations
(C++11)(C++11)(C++11)
(C++11)(C++11)(C++11)
(C++11)(C++11)(C++11)
(C++11)(C++11)(C++11)
(C++11)(C++11)(C++11)
(C++11)(C++11)(C++11)
(C++11)(C++11)(C++11)
(C++11)(C++11)(C++11)
(C++11)
(C++17)(C++17)(C++17)(C++17)
Relationships and property queries
(C++11)
(C++11)
(C++11)
(C++17)(C++17)(C++17)(C++17)
Type modifications
(C++11)(C++11)(C++11)
(C++11)(C++11)(C++11)
(C++11)
(C++11)
Type transformations
(C++11)
(C++11)
(C++11)
(C++20)
(C++11)
(C++17)
(C++11)
(C++11)
(C++20)
(C++11)
(C++11)(until C++20)(C++17)
(C++20)
 
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

T - 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

Run this code
#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

See also

(C++11)
 checks if a type is a lvalue reference
(class template)
(C++11)
 checks if a type is either a lvalue reference or rvalue reference
(class template)
Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/types/is_rvalue_reference&oldid=97254"