C++ – Is “enum class” a Class Type?

c++c++11c++17enums

I read about enumeration declaration in C++ using cppreference.

Then I have made Enum class and check whether it is a class type or not using std::is_class. 

#include <iostream>

enum class Enum 
{
    red = 1, blue, green
};

int main() 
{
    std::cout << std::boolalpha;
    std::cout << std::is_class<Enum>::value << '\n';
}

Then I compiled and ran in G++ compiler on Linux platform, it prints false value.

So Is enum class type or not? If enum is a class type, then why I'm getting false value?

Best Answer

enum class is not a class definition - the combination of keywords is used to define a scoped enumeration, which is a completely separate entity from a class.

std::is_class correctly returns false here. If you use std::is_enum, it will return true.

From the Standard:

The enumeration type declared with an enum-key of only enum is an unscoped enumeration, and its enumerators are unscoped enumerators. The enum-keys enum class and enum struct are semantically equivalent; an enumeration type declared with one of these is a scoped enumeration, and its enumerators are scoped enumerators.

There is no mention of an enum class being a "class type" anywhere in the Standard.

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