defmodule MyList do
  def max([]), do: nil
  def max([head | tail]), do: findmax(head, head, tail)

  defp findmax(current, _next, [head | tail]) do
    if head > current, do: findmax(head, current, tail), else: findmax(current, current, tail)
  end

  defp findmax(current, next, []) do
    if current > next, do: current, else: next
  end
end