This chapter began by explaining why FP matters, and then it introduced the key paradigms of FP in general. Furthermore, it introduced the basics of the Swift programming language with code examples. At this point, we should have a broad view of FP concepts and the Swift programming language. All the topics in this chapter will be covered in detail in the upcoming chapters.

We will begin to dive deeper into these topics with functions, as they are the most essential building blocks in FP. Therefore, the following chapter will explain functions and give examples for pure, first-class, higher-order, and nested functions. Also, it will explain slightly more advanced topics such as memoization, function currying, and composition.