lec03 generic servers

lectures/03/arithmetic.ex

@@ -0,0 +1,32 @@
+defmodule Arithmetic.Worker do
+    use GenServer
+
+    ### Client API ###
+    def start() do
+        GenServer.start(__MODULE__, nil)
+    end
+
+    def square(pid, x) do
+      GenServer.call(pid, {:square, x})
+    end
+
+    def sqrt(pid, x) do
+      GenServer.call(pid, {:sqrt, x})
+    end
+
+    ### Server Impl ###
+    @impl true
+    def init(_arg) do
+        {:ok, nil}
+    end
+
+    @impl true
+    def handle_call({:square, x}, _from, state) do
+      {:reply, x * x, state}
+    end
+
+    @impl true
+    def handle_call({:sqrt, x}, _from, state) do
+      {:reply, (if x < 0, do: :error, else: :math.sqrt(x)), state}
+    end
+end