Question

Is there a way in C++ to extend/”inherit” enums?

I.E:

enum Enum {A,B,C};
enum EnumEx : public Enum {D,E,F};

or at least define a conversion between them?

Answer 1

No, there is not.

enum are really the poor thing in C++, and that’s unfortunate of course.

Even the class enum introduced in C++0x does not address this extensibility issue (though they do some things for type safety at least).

The only advantage of enum is that they do not exist: they offer some type safety while not imposing any runtime overhead as they are substituted by the compiler directly.

If you want such a beast, you’ll have to work yourself:

• create a class MyEnum, that contains an int (basically)
• create named constructors for each of the interesting values

you may now extend your class (adding named constructors) at will…

That’s a workaround though, I have never found a satistifying way of dealing with an enumeration…