When you want to write a function that behaves differently depending on the type of its arguments, you’re looking at a polymorphic function. Elixir protocols give you a tidy and controlled way to implement this. Whether you’re integrating your types into the existing Elixir library or creating a new library with a flexible interface, protocols let you package the behaviour in a well-documented and disciplined way.
And with that, we’re almost done. But when you write about a language, there are always little details that don’t seem to fit anywhere. That’s why the next chapter is full of odds and ends.