A fibonacci number generator that is pretty quick written in Elixir

better_fib.exs

defmodule BetterFib do
  # Fib Calculator that pushes totals forward
  def fib(num) when is_number(num) and num == 0, do: 0
  def fib(num) when is_number(num) and num == 1, do: 1

  def fib(num) when is_number(num) and num >= 2 do
    numList = Enum.to_list(2..num)
    fib(0, 1, num, numList)
  end

  def fib(_minusTwo, answer, _num, []), do: answer

  def fib(minusTwo, minusOne, _prevAnswer, [currentIndex | numList]) when is_list(numList) do
    current = minusOne + minusTwo
    fib(minusOne, current, currentIndex, numList)
  end
end