Adds koans about tasks

lib/koans/11_task.ex

@@ -0,0 +1,49 @@
+defmodule Tasks do
+  use Koans
+
+  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 == 10
+  end
+
+  koan "if you don't need a result, use start_link/1" do
+    {:ok, pid} = Task.start_link(fn -> 1+1 end)
+  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) == nil
+    assert Task.await(handle) == 9
+  end
+
+  koan "tasks can be aborted with shutdown" do
+    handle = Task.async(fn ->
+                             :timer.sleep(100)
+                             3 * 3
+                         end)
+    refute Task.shutdown(handle)
+  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, 9}
+  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 == [1,4,9,16]
+  end
+
+  def do_other_stuff do
+    :timer.sleep(50)
+  end
+end

lib/runner.ex

@@ -9,7 +9,8 @@ defmodule Runner do
     Arithmetic,
     Structs,
     PatternMatching,
-    Processes
+    Processes,
+    Tasks
   ]
 
   def run do