ex01.exs

defmodule Ex01 do

  @moduledoc """

  In this exercise you'll implement a simple process that acts as a
  counter. Each time you send it `{:next, from}`, it will send to
  `from` the tuple `{:next_is, value}`, and that value will increase
  by one on each call. You code will allow you to set the initial
  value returned.

  The tests in the following module are commented out.

  You'll uncomment each in turn, and then write the code in the
  Ex01 module to make that test pass. You've finished when all the
  tests are uncommented and pass.

  Do NOT use the Task or Agent libraries for this test.

  ------------------------------------------------------------------
  ## For each test (2 in all):  10

        6 does the code compile and pass the tests
        2 is the program written in an idiomatic style that uses
          appropriate and effective language and library features
        2 is the program well laid out,  appropriately using indentation,
          blank lines, vertical alignment
  """
  
  def counter(value \\ 0) do
  end

end

ExUnit.start()

defmodule Test do
  use ExUnit.Case

  # Start by uncommenting this test and getting it to pass
  # This test assumes you have a function `counter` that can be spawned
  # and which handles the `{:next, from}` message

  # test "basic message interface" do
  #   count = spawn Ex01, :counter, []
  #   send count, { :next, self }
  #   receive do
  #     { :next_is, value } ->
  #       assert value == 0
  #   end
  # 
  #   send count, { :next, self }
  #   receive do
  #     { :next_is, value } ->
  #       assert value == 1
  #   end
  # end

  # then uncomment this one
  # Now we add two new functions to Ex01 that wrap the use of
  # that counter function, making the overall API cleaner

  # test "higher level API interface" do
  #   count = Ex01.new_counter(5)
  #   assert  Ex01.next_value(count) == 5
  #   assert  Ex01.next_value(count) == 6
  # end

end