| Defined in header <type_traits> | ||
|---|---|---|
template< class T > struct is_lvalue_reference; | (since C++11) |
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 > constexpr bool is_lvalue_reference_v = is_lvalue_reference<T>::value; | (since C++17) |
Inherited from std::integral_constant
Member constants
| value [static] | true if T is an lvalue reference type , false otherwise (public static member constant) |
Member functions
| operator bool | converts the object to bool, returns value (public member function) |
| operator() (C++14) | 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_lvalue_reference : std::false_type {};
template<class T> struct is_lvalue_reference<T&> : std::true_type {}; |
Example
#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
See also
| (C++11) | checks if a type is either lvalue reference or rvalue reference (class template) |
| (C++11) | checks if a type is rvalue reference (class template) |
| std::experimental::is_lvalue_reference_v
(library fundamentals TS) | variable template alias of std::is_lvalue_reference::value (variable template) |
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