Programming Elixir ≥ 1.6

Turning Our Sequence Program into an OTP Application

So, here’s the good news. The application here is already a full-blown OTP application. When mix created the initial project tree, it added a supervisor (which we then modified) and enough information to our mix.exs file to get the application started. In particular, it filled in the application function:

def application do
  [
    mod: {
      Sequence.Application, []
    },
    extra_applications: [:logger],
  ]
end

This says that the top-level module of our application is called Sequence. OTP assumes this module will implement a start function, and it will pass that function an empty list as a parameter.

In our previous version of the start function, we ignored the arguments and instead hard-wired ...