Reactive Design Patterns

Chapter 9. Nondeterminism by need

This chapter is the most abstract part of this book, and it is not required for initial understanding of the later chapters. You are welcome to skip ahead to chapter 10, as long as you promise to come back here at a later time.

In chapter 3, we introduced functional programming as one of the tools of the Reactive trade. The second part of this book has up to this point been concerned with splitting a problem into encapsulated modules that interact only via asynchronous message passing, an act that is fundamentally impure: sending a message to an external object implies that the state change of that other object cannot be modeled within the sender. It is necessarily a side effect. That is not incidental; it ...