Part 3. Common structures in functional design

We’ve now written a number of libraries using the principles of functional design. In part 2, we saw these principles applied to a few concrete problem domains. By now you should have a good grasp of how to approach a programming problem in your own work while striving for compositionality and algebraic reasoning.

Part 3 takes a much wider perspective. We’ll look at the common patterns that arise in functional programming. In part 2, we experimented with various libraries that provided concrete solutions to real-world problems, and now we want to integrate what we’ve learned from our experiments into abstract theories that describe the common structure among those libraries.