A class interface can be deceptively simple. Even though it may consist of only a few functions, those few functions may confound a number of distinct concepts. Consider, for instance, a class whose interface consists of only three functions: getStandingBlueBall(), getSittingRedDoor(), and getRunningYellowDog(). There are, in fact, three distinct concepts bound up in this interface: action (standing, sitting, or running), color (blue, red, or yellow), and object (ball, door, or dog). Although these three functions are named in accordance with their respective purposes, these single-token names do not clearly distinguish the three aforementioned concepts. Using object-oriented techniques, you can better "unpack" a class interface to distinguish the various concepts bound up in it. To illustrate these techniques, consider how best to implement the interface to a polar array class.
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