recursive_1.ex

deltas = loop([], nil, measurements)

  defp loop(acc, prev, list) do
    case list do
      [] -> acc
      [head | tail] when prev == nil -> loop(acc, head, tail)
      [head | tail] ->
        delta = (head.value - prev.value) / diff_string_date(prev.date, head.date)
        loop([delta | acc], head, tail)
    end
  end