a class-based society的用法和样例：
- The constructor initializer list supplies initial values for a class' base class and members.It does not specify the order in which those initializations are done.
- Pele was in a class of his own as a footballer.
- Every type should be based on a class.
- He is not so sick but he can attend a class.
- Her mother's cakes are in a class by themselves.