pmap.ex

 def map(collection, fun \\ &(&1)) do
    map_impl(collection, &spawn/1, &(invoke(fun, &1)))
  end

  def map!(collection, fun \\ &(&1)) do
    map_impl(collection, &spawn_link/1, fun)
  end

  defp map_impl(collection, spawn_fun, fun) do
    me = self
    collection
    |> Enum.map(fn (elem) ->
         spawn_fun.(fn -> (send me, { self, fun.(elem) }) end)
       end)
    |> Enum.map(fn (pid) ->
         receive do { ^pid, result } -> result end
       end)
  end

  defp invoke(fun, elem) do
    try do
      {:ok, fun.(elem)}
    rescue
      e -> {:error, e}
    end
  end