EXPLORATION 38

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Virtual Functions

Deriving classes is fun, but there’s not a lot you can do with them—at least, not yet. The next step is to see how C++ implements type polymorphism, and this Exploration starts you on that journey.

Type Polymorphism

Recall from Exploration 36 that type polymorphism is the ability of a variable of type B to take the “form” of any class derived from B. The obvious question is: “How?” The key in C++ is to use a magic keyword to declare a member function in a base class and also implement the function in a derived class with a different magic word. The magic keyword tells the compiler that you want to invoke type ...

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