Add bang-bang controller.

lib/bangbang_controller.ex

@@ -0,0 +1,11 @@
+defmodule ControlLoop.BangBangController do
+  require Record
+
+  Record.defrecord(:bb_controller, setpoint: 0, output_off: 0, output_on: 0)
+
+  def update( bb_controller(setpoint: setpoint, output_off: output_off, output_on: output_on) = controller, input) do
+    output = if input > setpoint, do: output_on, else: output_off
+
+    {output, controller}
+  end
+end

lib/control_loop.ex

@@ -2,17 +2,4 @@ defmodule ControlLoop do
   @moduledoc """
   Documentation for `ControlLoop`.
   """
-
-  @doc """
-  Hello world.
-
-  ## Examples
-
-      iex> ControlLoop.hello()
-      :world
-
-  """
-  def hello do
-    :world
-  end
 end

lib/pid_controller.ex

@@ -0,0 +1,3 @@
+defmodule ControlLoop.PIDController do
+
+end

test/bang_bang_controller_test.exs

@@ -0,0 +1,30 @@
+defmodule BangBangControllerTest do
+  use ExUnit.Case
+  import ControlLoop.BangBangController, only: :macros
+  alias ControlLoop.BangBangController
+
+  describe "setup" do
+    test "basic creating and fetching" do
+      c = bb_controller(setpoint: 1, output_off: 2, output_on: 3)
+
+      assert bb_controller(c, :setpoint) == 1
+      assert bb_controller(c, :output_off) == 2
+      assert bb_controller(c, :output_on) == 3
+    end
+  end
+
+  describe "updating" do
+    setup do
+     %{c:  bb_controller(setpoint: 1, output_off: 2, output_on: 3)}
+    end
+    test "update returns off value for below or at setpoint", %{c: controller} do
+      assert { 2, controller } == BangBangController.update(controller, 0)
+      assert { 2, controller } == BangBangController.update(controller, 1)
+    end
+
+    test "update returns on value for above setpoint", %{c: controller} do
+      assert { 3, controller } == BangBangController.update(controller, 2)
+    end
+  end
+
+end