Data commit

Task/Cumulative-standard-deviation/Elixir/cumulative-standard-deviation.elixir

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+defmodule Standard_deviation do
+  def add_sample( pid, n ), do: send( pid, {:add, n} )
+
+  def create, do: spawn_link( fn -> loop( [] ) end )
+
+  def destroy( pid ), do: send( pid, :stop )
+
+  def get( pid ) do
+    send( pid, {:get, self()} )
+    receive do
+      { :get, value, _pid } -> value
+    end
+  end
+
+  def task do
+    pid = create()
+    for x <- [2,4,4,4,5,5,7,9], do: add_print( pid, x, add_sample(pid, x) )
+    destroy( pid )
+  end
+
+  defp add_print( pid, n, _add ) do
+    IO.puts "Standard deviation #{ get(pid) } when adding #{ n }"
+  end
+
+  defp loop( ns ) do
+    receive do
+      {:add, n} -> loop( [n | ns] )
+      {:get, pid} ->
+        send( pid, {:get, loop_calculate( ns ), self()} )
+        loop( ns )
+      :stop -> :ok
+    end
+  end
+
+  defp loop_calculate( ns ) do
+    average = loop_calculate_average( ns )
+    :math.sqrt( loop_calculate_average( for x <- ns, do: :math.pow(x - average, 2) ) )
+  end
+
+  defp loop_calculate_average( ns ), do: Enum.sum( ns ) / length( ns )
+end
+
+Standard_deviation.task