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is_rvalue_reference Template in C++
In this article we will be discussing the working, syntax and examples of std::is_rvalue_reference template in C++ STL. is_rvalue_reference template in C++ is used to check whether the defined type is a rvalue reference or not.
What is an rvalue?
Rvalues are the values which are on the right side of an assignment operator. Rvalues are the value
What is rvalue reference?
Rvalue reference is identified by double ampersand symbol (&&). This is used to initialise it with only the rvalue value.
Syntax
int&& a;
Syntax
template <class T> is_rvalue_reference;
Parameters
The template can have only parameter of type T, and check whether the given type is a rvalue reference or not
Return value
It returns a Boolean value, true if the given value is an rvalue reference, and false if the given value is not an rvalue reference or when we are referencing an unknown location.
Example
Input: is_rvalue<int&>::value; Output: False Input: is_rvalue<int&&>::value; Output: True
Example
#include <iostream>
#include <type_traits>
using namespace std;
int main() {
cout << std::boolalpha;
cout << "Checking for is_lvalue_reference: ";
cout << "\nint : "<<is_rvalue_reference<int>::value;
cout << "\nint& : "<< is_rvalue_reference<int&>::value;
cout << "\nint&&: "<< is_rvalue_reference<int&&>::value;
cout << "\nchar : "<<is_rvalue_reference<char>::value;
cout << "\nchar& : "<< is_rvalue_reference<char&>::value;
cout << "\nchar&&: "<< is_rvalue_reference<char&&>::value;
cout << "\nfloat : "<<is_rvalue_reference<float>::value;
cout << "\nfloat& : "<< is_rvalue_reference<float&>::value;
cout << "\nfloat&&: "<< is_rvalue_reference<float&&>::value;
cout << "\ndouble : "<<is_rvalue_reference<double>::value;
cout << "\ndouble& : "<< is_rvalue_reference<double&>::value;
cout << "\ndouble&&: "<< is_rvalue_reference<double&&>::value;
return 0;
}Output
If we run the above code it will generate the following output −
Checking for is_rvalue_reference: int : false int& : false int&&: ture char : false char& : false char&&: ture float : false float& : false float&&: ture double: false double : false double&&: ture
Example
#include <iostream>
#include <type_traits>
using namespace std;
class TP {
};
int main() {
cout << std::boolalpha;
cout << "Checking for is_lvalue_reference: ";
cout << "\nTP class : "<<is_rvalue_reference<TP>::value;
cout << "\nTP& : "<< is_rvalue_reference<TP&>::value;
cout << "\nTP&&: "<< is_rvalue_reference<TP&&>::value;
return 0;
}Output
If we run the above code it will generate the following output −
Checking for is_rvalue_reference: TP class : false TP& : false TP&&: true
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