C++ Primer Plus

How Many Workers?

Suppose you begin by publicly deriving SingingWaiter from Singer and Waiter:

class SingingWaiter: public Singer, public  Waiter {...};

Because both Singer and Waiter inherit a Worker component, SingingWaiter winds up with two Worker components (see Figure 14.4).

Figure 14.4. Inheriting two base-class objects.

As you might expect, this raises problems. For example, ordinarily you can assign the address of a derived-class object to a base-class pointer, but this becomes ambiguous now:

SingingWaiter ed;Worker * pw = &ed;   // ambiguous

Normally, such an assignment sets a base-class pointer to the address of the base-class object ...