Arrow is a great project that give us many possibilities to manage null values, create composed accessors among many other functionalities. One of the things that I trully enjoy about this project is that it provides an easy way to create code and access values in our data structures using something called optics. This is only an example. Arrow Optics implement a pattern that allows us to use Lens, which is another feature of it, and that enable us to create easy access to complex types that are structured in the form of a tree. I find this project fascinating.