std::is_reference

 

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Defined in header <type_traits>
template< class T > struct is_reference;		(since C++11)

If T is a reference type (lvalue reference or rvalue reference), provides the member constant value equal true. For any other type, value is false.

Inherited from std::integral_constant

Member constants

value [static]	true if T is a reference type , false otherwise (public static member constant)

Member functions

operator bool	converts the object to bool, 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_reference : std::false_type {}; template <class T> struct is_reference<T&> : std::true_type {}; template <class T> struct is_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_reference<A>::value << '\n';
    std::cout << std::is_reference<A&>::value << '\n';
    std::cout << std::is_reference<A&&>::value << '\n';
    std::cout << std::is_reference<int>::value << '\n';
    std::cout << std::is_reference<int&>::value << '\n';
    std::cout << std::is_reference<int&&>::value << '\n';
}

Output:

false
true
true
false
true
true

See also

is_lvalue_reference (C++11)	checks if a type is lvalue reference (class template)
is_rvalue_reference (C++11)	checks if a type is rvalue reference (class template)