Er, I've never used a OO language that didn't allow you to add new operations freely without modifying a class. Not all of them allow you to add new methods, s

Er, I've never used a OO language that didn't allow you to add new operations freely without modifying a class. Not all of them allow you to add new methods, sure, but new functions and operators are par for the course. And surely you're not arguing the defining feature of a class is that it's closed?