Reposition MapSets koans. Reposition some of the koans to make it clear why MapSets are interesting.

lib/koans/16_tasks.ex

@@ -0,0 +1,55 @@
+defmodule Tasks do
+  use Koans
+
+  @intro "Tasks"
+
+  koan "Tasks can be used for asynchronous computations with results" do
+    task = Task.async(fn -> 3 * 3 end)
+    do_other_stuff()
+    assert Task.await(task) + 1 == ___
+  end
+
+  koan "If you don't need a result, use start_link/1" do
+    {result, _pid} = Task.start_link(fn -> 1+1 end)
+    assert result == ___
+  end
+
+  koan "Yield returns nil if the task isn't done yet" do
+    handle = Task.async(fn ->
+                             :timer.sleep(100)
+                             3 * 3
+                         end)
+    assert Task.yield(handle, 10) == ___
+  end
+
+  koan "Tasks can be aborted with shutdown" do
+    handle = Task.async(fn ->
+                             :timer.sleep(100)
+                             3 * 3
+                         end)
+
+    %Task{pid: pid} = handle
+    Task.shutdown(handle)
+
+    assert Process.alive?(pid) == ___
+  end
+
+  koan "Shutdown will give you an answer if it has it" do
+    handle = Task.async(fn -> 3 * 3 end)
+    :timer.sleep(10)
+    assert Task.shutdown(handle) == {:ok, ___}
+  end
+
+  koan "You can yield to multiple tasks at once and extract the results" do
+    squares = [1 ,2 ,3 ,4]
+             |> Enum.map(fn(number) -> Task.async(fn -> number * number end) end)
+             |> Task.yield_many(100)
+             |> Enum.map(fn({_task,{:ok, result}}) -> result end)
+
+    assert squares == ___
+  end
+
+  def do_other_stuff do
+    :timer.sleep(50)
+  end
+end