std:: is_lvalue_reference

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

std::is_lvalue_reference is a UnaryTypeTrait .

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

If the program adds specializations for std::is_lvalue_reference or std::is_lvalue_reference_v , the behavior is undefined.

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

Run this code 
#include <type_traits>
 
class A {};
static_assert(std::is_lvalue_reference_v<A> == false);
static_assert(std::is_lvalue_reference_v<A&> == true);
static_assert(std::is_lvalue_reference_v<A&&> == false);
 
static_assert(std::is_lvalue_reference_v<int> == false);
static_assert(std::is_lvalue_reference_v<int&> == true);
static_assert(std::is_lvalue_reference_v<int&&> == false);
 
int main() {}

See also

(C++11)
checks if a type is either an lvalue reference or rvalue reference
(class template)
(C++11)
checks if a type is an rvalue reference
(class template)
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