The Strategy pattern should be considered whenever we design a system that does certain operations, but the exact implementation of these operations is uncertain, varied, or can change after the system is implemented—in other words, when we know the answer to what the system must do, but not how. Similarly, the compile-time strategy, or a policy, is a way to implement a class that has a specific function (what), but there is more than one way to implement that function (how).
Throughout this chapter, we will, to illustrate different ways to use policies, design a smart pointer class. A smart pointer has many other required and optional features besides policies, and we will not cover all of them—for a complete ...
