# std::is_lvalue_reference

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< cpp‎ | types

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

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)

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