Counter with no Enum

counter.exs

defmodule AncientEgyptianMultiplication do  
  def count_of([_head | tail]) do
    count_of(tail, 1)
  end
  def count_of([], state), do: state
  def count_of([_head | tail], state) do
    count_of(tail, state + 1)
  end
end