This chapter has given us the technique for repeating the function invocation by using iteration and recursion. However, since recursion is more functional than iteration, we emphasized our discussion on recursion instead of iteration. We started with the difference between iteration and recursion. We then continued the discussion about refactoring the immutable function to become a recursive immutable function.
After we learned about the recursion, we found other better recursion techniques. We also discussed tail recursion to get this improved technique. Lastly, we enumerated three kinds of recursion--functional, procedural, and backtracking recursion. We usually use functional recursion when we expect the return value for the recursion. Otherwise, we use procedural recursion. And, if we need to break down the problem and undo the recursion performance when it doesn't work, we can use backtracking recursion to solve the problem.
In the next chapter, we will discuss lazy evaluation...