4.5 Exercises, 2. Write a foo function and make it called from a class that has a foo method.
4.5 Exercises, 3. Write a Real base class and a derived Integer class with all common operators (+,-,*,/)
4.5 Exercises, 4. Write a Singleton class such that only one object of this class can be created.
+ Updated zzz.cpp template for future exercises.
4.5 Exercises, 5. Write a functor class.