Whoever tries to learn Scala immediately encounters talk about Functional Programming.

The first step is having functions as first-class citizens. This opens up new ways of programming, and the Scala collection library if far superior to Java's because of it. There are many examples of how boilerplate loops of creating and populating new collections can be replaced by a succint one liner of using `map`.

In this post I'll try to explain the more advanced concepts of Functors, Applicatives and Monads. I'm doing it starting from everyday OO and building the API and the implementation as we go along.

(Note: This paper was not easy to write and may still be confusing despite my best efforts. I would love to hear your thoughts and suggestions in the comments, or through twitter: @ittayd)