std::is_lvalue_reference (3) - Linux Manuals

std::is_lvalue_reference: std::is_lvalue_reference

NAME

std::is_lvalue_reference - std::is_lvalue_reference

Synopsis

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

Checks whether T is a lvalue reference type. Provides the member constant value which is equal to true, if T is a lvalue reference type. Otherwise, value is equal to false.

Template parameters

T - a type to check

Helper variable template

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

Inherited from std::integral_constant

Member constants

value true if T is an lvalue 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_lvalue_reference : std::false_type {};
  template<class T> struct is_lvalue_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_lvalue_reference<A>::value << '\n';
      std::cout << std::is_lvalue_reference<A&>::value << '\n';
      std::cout << std::is_lvalue_reference<A&&>::value << '\n';
      std::cout << std::is_lvalue_reference<int>::value << '\n';
      std::cout << std::is_lvalue_reference<int&>::value << '\n';
      std::cout << std::is_lvalue_reference<int&&>::value << '\n';
  }

Output:

  false
  true
  false
  false
  true
  false