Functional Reactive Programming - Stephen Blackheath, Anthony Jones

GoodReads Summary Functional Reactive Programming teaches the concepts and applications of FRP. It begins with a careful walk-through of the FRP core operations and introduces the concepts and techniques you'll need to use FRP in any language. Following easy-to-understand examples, you'll learn both how to use FRP in greenfield applications and how to refactor existing applications. Along the way, the book introduces the basics of functional programming in a just-in-time style, so you never learn anything before you need to use it. When you're finished, you'll be able to use FRP to spend more time adding features and less time fixing problems.

• (-) Some phrases are a bit hard to read. Maybe it's because I'm not a native English speaker¹, but some are akin to "my beautiful nature photos", which you can read in different ways ("my beautiful photos of nature", "my photos of beautiful nature") and I had to backtrack and read the whole thing again.
• (-) Code listings are a mess: long and with no separation of concerns. It is ok if you use lambdas for simpler functions, but when you keep piling lambdas over lambdas, things get a bit out of hand. Trying to explain some functionality in a 200 line function is not actually helpful.
• (-) The ePub version seriously need another check. Some code listings are pure text, following the font size the user set in their reader; other are screenshots/images of code, which get way out of hand, as some of those had a font 1/5 of the size I set up (yes, I use a large font, I'm reading at night without my glasses, but the point remains).
• (--) There is very little explanation on what FRP really is, but a lot about how to do things with Sodium, the authors' library. Instead of focusing on how to build your own FRP system, using Sodium as reference, the book focuses a lot in using Sodium and its relationship with FRP instead of explaining the concept behind the FRP functionality itself.
• (--) The authors show some weird prejudices against TDD. For example, they say that FRP doesn't require TDD and that using TDD is actually harmful for FRP (!!²), "unless you test logic" (???³). I have to ask: Seriously? What do you think TDD is about? Lines of code? TDD says that "tests should validate behaviors, not implementation" and I'm wondering why the authors are so reticent against TDD when their concept of TDD seems completely out of place.
• (---) There is a strong gatekeeping in the book. While talking about other frameworks, the authors decided to focus more on "why this framework is not pure FRP, while Sodium is" instead of, again, focusing on the concepts of FRP itself. "FRP says so and so, you can build this with framework X using that and that" is a good way to do it; "FRP says so and so, framework X do this which is not what the FRP says, so framework X is not FRP, but Sodium is!" is a dickish way to downplay other frameworks. Not only that, but every time Sodium break some FRP rule (rules that the authors themselves keep listing), they put a long explanation on why it's ok for you to break the rule there when using Sodium, but Sodium, although requiring you to break some FRP rule, is actually a pure-FRP framework, and not those pesky other frameworks that are not pure-FRP frameworks.

Honestly, I read the book and I still don't understand FRP; all I got was some concepts for a Sodium framework.