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Pre-assessment notes

Subclassing

The key things I wanted you to say were: subclassing lets you use object oriented polymorphism (this is far more important than that it lets you save a little typing); but it introduces tight coupling between the subclass and the superclass. To decide when it's sensible to make T a subclass of S, the main thing you should ask yourself is: is it true that every T is an S? The reason why this is the right question is that then, a client written to handle Ss should indeed be able to handle Ts automatically, which is what OO polymorphism will give you.

Very few people said what I wanted you to say, which goes along with few people understanding OO polymorphism. We'll talk about this. I'm glad I asked!

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