is_lvalue_reference Template in C++

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

Syntax: 

template <class T > struct is_lvalue_reference;

Template Parameter: This template accepts a single parameter T (Trait class) to check whether T is a lvalue reference type or not.



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

  • True: if the type is a lvalue_reference.
  • False: if the type is a non-lvalue_reference.

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

Program 1:

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

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Output: 


is_lvalue_reference: 
gfg: false
gfg&: true
gfg&&: false





Program 2: 











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// C++ program to illustrate 


// std::is_lvalue_reference template 


  


#include <iostream> 


#include <type_traits> 


using namespace std; 


  


// main program 


int main() 


{ 


  


    cout << boolalpha; 


    cout << "is_lvalue_reference: "


         << '\n'; 


    cout << "int: "


         << is_lvalue_reference<int>::value 


         << '\n'; 


    cout << "int&: "


         << is_lvalue_reference<int&>::value 


         << '\n'; 


    cout << "int&&: "


         << is_lvalue_reference<int&&>::value 


         << '\n'; 


    cout << "char: "


         << is_lvalue_reference<char>::value 


         << '\n'; 


    cout << "char&: "


         << is_lvalue_reference<char&>::value 


         << '\n'; 


    cout << "char&&: "


         << is_lvalue_reference<char&&>::value 


         << '\n'; 


  


    return 0; 


} 



















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Output: 


is_lvalue_reference: 
int: false
int&: true
int&&: false
char: false
char&: true
char&&: false





Program 3: 











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// C++ program to illustrate 


// std::is_lvalue_reference template 


  


#include <iostream> 


#include <type_traits> 


using namespace std; 


  


// main program 


int main() 


{ 


  


    cout << boolalpha; 


    cout << "is_lvalue_reference: "


         << '\n'; 


    cout << "float: "


         << is_lvalue_reference<float>::value 


         << '\n'; 


    cout << "float&: "


         << is_lvalue_reference<float&>::value 


         << '\n'; 


    cout << "float&&: "


         << is_lvalue_reference<float&&>::value 


         << '\n'; 


    cout << "double: "


         << is_lvalue_reference<double>::value 


         << '\n'; 


    cout << "double&: "


         << is_lvalue_reference<double&>::value 


         << '\n'; 


    cout << "double&&: "


         << is_lvalue_reference<double&&>::value 


         << '\n'; 


  


    return 0; 


} 



















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Output: 


is_lvalue_reference: 
float: false
float&: true
float&&: false
double: false
double&: true
double&&: false







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