Exercise 42: Is-A, Has-A, Objects, and Classes

An important concept that you have to understand is the difference between a class and an object. The problem is, there is no real "difference" between a class and an object. They are actually the same thing at different points in time. I will demonstrate by a Zen koan:

What is the difference between a fish and a salmon?

Did that question sort of confuse you? Really sit down and think about it for a minute. I mean, a fish and a salmon are different but, wait, they are the same thing, right? A salmon is a kind of fish, so I mean it's not different. But at the same time, a salmon is a particular type of fish so it's actually different from all other fish. That's what makes it a salmon and not a halibut. So a salmon and a fish are the same but different. Weird.

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