std::is_reference (3) - Linux Manuals

std::is_reference: std::is_reference


std::is_reference - std::is_reference


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

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.

Template parameters

T - a type to check

Helper variable template

template< class T > (since C++17)
inline constexpr bool is_reference_v = is_reference<T>::value;

Inherited from std::integral_constant

Member constants

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

Member functions

              converts the object to bool, returns value
operator bool (public member function)

operator() 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 {};


// 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';



See also

is_lvalue_reference checks if a type is a lvalue reference
                    (class template)

is_rvalue_reference checks if a type is a rvalue reference
                    (class template)