std::is_reference - cppreference.com (original) (raw)
| | | | | ------------------------------------------ | | ------------- | | template< class T > struct is_reference; | | (since C++11) |
std::is_reference is a UnaryTypeTrait.
If T is a reference type (lvalue reference or rvalue reference), provides the member constant value equal true. For any other type, value is false.
If the program adds specializations for std::is_reference or std::is_reference_v, the behavior is undefined.
Contents
[edit] Template parameters
[edit] Helper variable template
| template< class T > constexpr bool is_reference_v = is_reference<T>::value; | | (since C++17) | | --------------------------------------------------------------------------------- | | ------------- |
Inherited from std::integral_constant
Member constants
| | true if T is a reference type, false otherwise (public static member constant) | | --------------------------------------------------------------------------------- |
Member functions
| | converts the object to bool, returns value (public member function) | | ---------------------------------------------------------------------- | | | returns value (public member function) |
Member types
[edit] Possible implementation
[edit] Example
#include #include class A {}; int main() {
define REF(x) << #x " ?: " << x << '\n'
[std::cout](../io/cout.html) << [std::boolalpha](../io/manip/boolalpha.html)
REF(std::is_reference_v<A>)
REF(std::is_reference_v<A&>)
REF(std::is_reference_v<A&&>)
REF(std::is_reference_v<long>)
REF(std::is_reference_v<long&>)
REF(std::is_reference_v<long&&>)
REF(std::is_reference_v<double*>)
REF(std::is_reference_v<double*&>)
REF(std::is_reference_v<double*&&>);undef REF
}
Output: