std::is_reference (3) - Linux Man Pages

std::is_reference: std::is_reference

NAME

std::is_reference - std::is_reference

Synopsis


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)
[static]

Member functions


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


operator() returns value
              (public member function)
(C++14)

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


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