return-tuples-with-ok-elixir#example-from-stack-overflow1
(from http://stackoverflow.com/questions/31192923/lists-vs-tuples-what-to-use-and-when here is an example)
"Contrast this with a typical use-case for tuples - returning {:ok, result} or {:error, reason} from a method - here the number of elements is known up-front and so you don't pay an unacceptable price for the performance improvements of Tuples."
return-tuples-with-ok-elixir#example-from-stack-overflow1