lecture 02

lectures/02/lec2.ex

@@ -0,0 +1,91 @@
+defmodule ArithmeticServer do
+  # --- Server Implementation ---
+  def start() do
+    spawn(&loop/0) # capture variable?
+  end
+
+  defp loop() do
+    receive do
+      {from, :square, x} ->
+        send(from, x * x)
+      {from, :square_root, x} ->
+        send(from, (if x < 0, do: :error, else: :math.sqrt(x)))
+    end
+    loop()
+  end
+
+  # --- Client API ---
+  def square(pid, x) do
+    send(pid, {self(), :square, x})
+    receive do
+      x -> x
+    end
+  end
+
+  def sqrt(pid, x) do
+    send(pid, {self(), :square_root, x})
+    receive do
+      x -> x
+    end
+  end
+end
+
+defmodule Counter do
+  # --- Server Implementation ---
+  def start(n \\ 0) do ## double backslash indicated default value, so n defaults to 0
+    spawn(fn -> loop(n) end)
+  end
+
+  defp loop(n) do
+    receive do
+      {from, :value} ->
+        send(from, n)
+        loop(n)
+      :inc ->
+        loop(n + 1)
+    end
+  end
+
+  ## --- Client API ---
+  def value(pid) do
+    send(pid, self(), :value)
+    receive do
+      x -> x
+    end
+  end
+
+  def inc(pid) do
+    send(pid, :inc)
+  end
+end
+
+# Registered processes dont need to remember process ID
+# we can refer to a process by the name when its registered
+defmodule RegisteredCounter do
+  # --- Server Implementation ---
+  def start(n \\ 0) do
+    Processs.register(spawn(fn -> loop(n) end), __MODULE__) ## __MODULE__ refers to current module name
+  end
+
+  defp loop(n) do
+    receive do
+      {from, :value} ->
+        send(from, n)
+        loop(n)
+      :inc ->
+        loop(n + 1)
+    end
+  end
+
+  # --- Client API ---
+  def value() do
+    send(__MODULE__, {self(), :value})
+    receive do
+      x -> x
+    end
+  end
+
+  def inc() do
+    send(__MODULE__, :inc)
+  end
+end