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Showing content from https://en.cppreference.com/w/cpp/language/../error/../language/../types/is_class.html below:

std::is_class - cppreference.com

template< class T > struct is_class;

(since C++11)

std::is_class is a UnaryTypeTrait.

Checks whether T is a non-union class type. Provides the member constant value which is equal to true, if T is a class type (but not union). Otherwise, value is equal to false.

If the program adds specializations for std::is_class or std::is_class_v, the behavior is undefined.

[edit] Template parameters [edit] Helper variable template

template< class T > constexpr bool is_class_v = is_class<T>::value;

(since C++17) Inherited from std::integral_constant Member constants true if T is a non-union class 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 <type_traits>
 
struct A {};
static_assert(std::is_class<A>::value);
 
class B {};
static_assert(std::is_class_v<B>);
static_assert(not std::is_class_v<B*>);
static_assert(not std::is_class_v<B&>);
static_assert(std::is_class_v<const B>);
 
enum class E {};
static_assert(not std::is_class<E>::value);
 
union U { class UC {}; };
static_assert(not std::is_class_v<U>);
static_assert(std::is_class_v<U::UC>);
 
static_assert(not std::is_class_v<int>);
 
static_assert(std::is_class_v<struct S>, "incomplete class");
static_assert(std::is_class_v<class C>, "incomplete class");
 
int main() {}

[edit] See also checks if a type is a union type
(class template) [edit]

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