Probably bad mean in elixir

math_mean.exs

defmodule FastMath do
  def mean([]), do: 0
  def mean([a]), do: a

  def mean(list) do
    _mean(list, 0, 0)
  end

  # terminal condition
  defp _mean([], total, count) do
    total / count
  end

  defp _mean([head|tail], total, count) do
    new_count = count + 1
    new_total = total + head
    _mean(tail, new_total, new_count)
  end

end