Many of the examples described in this book follow the functional programming paradigm. Since ReactiveX is already using several principals of functional programming, it is a natural way to structure such applications. However, only a subset of the functional programming principals will be used. The structure and separation of responsibilities that will be done in the code rely on the following:

• Lambdas and closure: These ease the readability of the code
• Side effects and pure functions: These allow you to write deterministic and testable code
• Higher-order functions: These are building blocks for many code constructs