基本のコード(純関数型)

stopwatchA.ex

defmodule StopwatchA do
  import System, only: [ monotonic_time: 1 ]
  
  def activate() do
    now = monotonic_time(100)
    {0, now}
  end
  
  def restart(last_time) do
    now = monotonic_time(100)
    {now - last_time, now}
  end
  
  def lap(last_time) do
    now = monotonic_time(100)
    {now - last_time, last_time}
  end
end