Programming Elixir 1.3

When Specifications Are Used

Elixir type specifications come from Erlang. It is very common to see Erlang code where every exported (public) function is preceded by a -spec line. This is metadata that gives type information. The following code comes from the Elixir parser (which is [currently] written in Erlang). It says the return_error function takes two parameters, an integer and any type, and never returns.

-spec return_error(integer(), any()) -> no_return().
return_error(Line, Message) ->
      throw({error, {Line, ?MODULE, Message}}).

One of the reasons the Erlang folks do this is to document their code. You can read it inline while reading the source, and you can also read it in the pages created by their documentation tool.

The other ...