After reading this book, you might be surprised (and possibly frustrated) by the fact that I didn’t talk about monads. Monads are a hot topic, and you can find many so-called “Monad tutorials” on the web. The topic of monads seems to be very intimidating, and many programmers read these tutorials one after the other in the hope that they’ll eventually understand what monads are. Of course, many other programmers do understand monads, but very few are able to explain monads in simple terms.
The reason why there are so many monad tutorials is probably because there’s no definitive tutorial, so people keep trying to roll their own. This appendix is not another monad tutorial. I wouldn’t want to write one for two reasons: