is_lvalue_reference Template in C++
Last Updated :
19 Nov, 2018
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:
#include <iostream>
#include <type_traits>
using namespace std;
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;
}
|
Output:
is_lvalue_reference:
gfg: false
gfg&: true
gfg&&: false
Program 2:
#include <iostream>
#include <type_traits>
using namespace std;
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;
}
|
Output:
is_lvalue_reference:
int: false
int&: true
int&&: false
char: false
char&: true
char&&: false
Program 3:
#include <iostream>
#include <type_traits>
using namespace std;
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;
}
|
Output:
is_lvalue_reference:
float: false
float&: true
float&&: false
double: false
double&: true
double&&: false
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