Or that OO is stupid?
Actually, it doesn’t mean any of these things. The sad reality is that it means your intuition is wrong. Look, I have received and answered dozens of passionate e-mail messages about this subject. I have taught it hundreds of times to thousands of software professionals all over the place. I know it goes against your intuition. But trust me; your intuition is wrong. The real problem is your intuitive notion of “kind of” doesn’t match the OO notion of proper inheritance (technically called “subtyping”). The bottom line is that the derived class objects must be substitutable for the base class objects. In the case of Circle/Ellipse, the setSize(x,y) member function violates this substitutability. You have three choices: [1] remove the setSize(x,y) member function from Ellipse (thus breaking existing code that calls the setSize(x,y) member function), [2] allow a Circle to have a different height than width (an asymmetrical circle; hmmm), or [3] drop the inheritance relationship. Sorry, bu
