Elixir 練習問題 ModulesAndFunctions-4

defmodule Sum do

  def sum(1), do: 1
  def sum(n), do: n + sum(n - 1)

end

^o^ > iex
Eshell V8.0  (abort with ^G)
Interactive Elixir (1.3.4) - press Ctrl+C to exit (type h() ENTER for help)
iex(1)> c "practice_6_4.exs"
[Sum]
iex(2)> Sum.sum(10)
55