is_rvalue_reference Template in C++

Last Updated : 19 Nov, 2018

The std::is_rvalue_reference template of C++ STL is used to check whether the type is a rvalue reference type or not. It returns a boolean value showing the same.

Syntax:

template <class T > struct is_rvalue_reference;

Parameters: This template accepts a single parameter T (Trait class) to check whether T is a rvalue reference type.

Return Value: This template returns a boolean value as shown below:

True: if the type is a rvalue_reference type.
False: if the type is a non-rvalue_reference type.

Below programs illustrate the std::is_lvalue_reference template in C++ STL:

Program 1:

// C++ program to illustrate 
// std::is_rvalue_reference template 
  
#include <iostream> 
#include <type_traits> 
using namespace std; 
  
// main program 
  
class gfg { 
}; 
  
int main() 
{ 
    cout << std::boolalpha; 
    cout << "is_rvalue_reference: "
         << '\n'; 
    cout << "gfg: "
         << is_rvalue_reference<gfg>::value 
         << '\n'; 
    cout << "gfg&: "
         << is_rvalue_reference<gfg&>::value 
         << '\n'; 
    cout << "gfg&&: "
         << is_rvalue_reference<gfg&&>::value 
         << '\n'; 
  
    return 0; 
} 

Output:

is_rvalue_reference: 
gfg: false
gfg&: false
gfg&&: true

Program 2:

// C++ program to illustrate 
// std::is_rvalue_reference template 
  
#include <iostream> 
#include <type_traits> 
using namespace std; 
  
// main program 
int main() 
{ 
  
    cout << std::boolalpha; 
    cout << "is_rvalue_reference: "
         << '\n'; 
    cout << "int: "
         << is_rvalue_reference<int>::value 
         << '\n'; 
    cout << "int&: "
         << is_rvalue_reference<int&>::value 
         << '\n'; 
    cout << "int&&: "
         << is_rvalue_reference<int&&>::value 
         << '\n'; 
    cout << "char: "
         << is_rvalue_reference<char>::value 
         << '\n'; 
    cout << "char&: "
         << is_rvalue_reference<char&>::value 
         << '\n'; 
    cout << "char&&: "
         << is_rvalue_reference<char&&>::value 
         << '\n'; 
  
    return 0; 
} 

Output:

is_rvalue_reference: 
int: false
int&: false
int&&: true
char: false
char&: false
char&&: true

Program 3:

// C++ program to illustrate 
// std::is_rvalue_reference template 
  
#include <iostream> 
#include <type_traits> 
using namespace std; 
  
// main program 
int main() 
{ 
    cout << std::boolalpha; 
    cout << "is_rvalue_reference: "
         << '\n'; 
    cout << "float: "
         << is_rvalue_reference<float>::value 
         << '\n'; 
    cout << "float&: "
         << is_rvalue_reference<float&>::value 
         << '\n'; 
    cout << "float&&: "
         << is_rvalue_reference<float&&>::value 
         << '\n'; 
    cout << "double: "
         << is_rvalue_reference<double>::value 
         << '\n'; 
    cout << "double&: "
         << is_rvalue_reference<double&>::value 
         << '\n'; 
    cout << "double&&: "
         << is_rvalue_reference<double&&>::value 
         << '\n'; 
  
    return 0; 
} 

Output:

is_rvalue_reference: 
float: false
float&: false
float&&: true
double: false
double&: false
double&&: true

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