Designing Elixir Systems With OTP

Build Your Functional Core

Now we’ll finally start coding. Our functional core is what some programmers call the business logic. This inner layer does not care about any of the machinery related to processes; it does not try to preserve state; and it has no side effects (or, at least, the bare minimum that we must deal with). It is made up of functions.

Our goal is to deal with complexity in isolation. Make no mistake, processes and side effects add complexity. Building our core allows us to isolate the inherent complexity of our domain from the complexity of the machinery we need to manage processes, handle side effects, and the like.

In a chess game, this logic would have functions that take a board, move an individual piece, and return an ...