Summary

In this chapter, we have studied, extensively, the applications of the Strategy pattern (also known as the policy pattern) to C++ generic programming. The combination of the two gives rise to one of the most powerful tools in the arsenal of a C++ programmer - the policy-based design of classes. This approach provides great flexibility by allowing us to compose the behavior of the class from many building blocks, or policies, each of which is responsible for a particular aspect of the behavior.

We have learned different ways to implement policies - these can be templates, classes with template member functions, classes with static functions, and even classes with constant values. Just as varied are the ways that we can use policies through composition, inheritance, or direct access to static members. Policy parameters can be types or templates, each with its own advantages and limitations.

A tool as powerful as the policy-based design is also easily misused or applied...