First commit

chapter5/calculator_refactor.ex

@@ -0,0 +1,35 @@
+defmodule Calculator do
+  def start do
+    spawn(fn -> loop(0) end)
+  end
+
+  defp loop(current_value) do
+    new_value =
+      receive do
+        message -> process_message(current_value, message)
+      end
+
+    loop(new_value)
+  end
+
+  defp process_message(current_value, {:value, caller}) do
+    send(caller, {:response, current_value})
+    current_value
+  end
+
+  defp process_message(current_value, {:add, value}) do
+    current_value + value
+  end
+
+  defp process_message(current_value, {:sub, value}) do
+    current_value - value
+  end
+
+  defp process_message(current_value, {:mul, value}) do
+    current_value * value
+  end
+
+  defp process_message(current_value, {:div, value}) do
+    current_value / value
+  end
+end