std::is_lvalue_reference

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

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 <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() {}

is_reference (C++11)	checks if a type is either an lvalue reference or rvalue reference (class template)
is_rvalue_reference (C++11)	checks if a type is an rvalue reference (class template)
is_lvalue_reference_type (C++26)	checks if reflection represents an lvalue reference (function)