std::is_reference

From Cppreference

Defined in header `<type_traits>`

template< class T > struct is_reference;		(C++11 feature)

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`	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>

[edit] Equivalent definition

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 {};

[edit] Example

#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

[edit] 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)