C++ Primer Plus

Redefining Access with using

Public members of a base class become protected or private when you use protected or private derivation. Suppose you want to make a particular base-class method available publicly in the derived class. One option is to define a derived-class method that uses the base-class method. For example, suppose you want the Student class to be able to use the valarray sum() method. You can declare a sum() method in the class declaration and then define the method this way:

double Student::sum() const    // public Student method{    return std::valarray<double>::sum(); // use privately-inherited method}

Then a Student object can invoke Student::sum(), which, in turn, applies the valarray<double>::sum() method to the embedded ...