Nice, although one thing to note is that although eex accepts ‘nil’, it should not really ever be used. Returning an empty list of [] is always a better approach than returning nil as it then allows it to be embedded further without worry. I consider nil’s returned from a function that could ever possibly end up going to a template as a bug.

Other than that your article looks like a fairly accurate high level view.

I honestly don’t think this is a good idea. Erlang uses nil to mean empty list only because that’s the naming in lisp. But I don’t think there’s a strong technical reason for it.

Erlang itself most often uses the atom undefined for uninitialised state, so I think using an atom for this purpose in elixir makes the most sense.

[] is not Erlang’s nil. That notation is used only in the abstract syntax tree and in Erlang code nil has exactly the same as nil in Elixir.

Plus [] has the notion of cardinality, which nil is devoid of. Given Elixir has both collections and base types, I believe it is important to represent nothingness without a notion of cardinality built-in.