Pmap in Elixir the old way

pmap.ex

defmodule Pmap do
  @moduledoc """
  Parrallel map calculator

  Calculates a result of a &function/1
  """

  @doc """
  emit a process, which calculates a number
  and sends a message
  """
  def emit(arg, main_ref) do
    spawn fn ->
      send(main_ref, {self(), function(arg)})
    end
  end

  def emit(arg, main_ref, func) do
    spawn fn ->
      send(main_ref, {self(), func.(arg)})
    end
  end

  @doc """
  listens on a process, blocks,
  matches exactly on the pid in order to preserve the place in the list
  """

  def listen(pid) do
    receive do
      {^pid, result} -> result
    end
  end

  @doc """
  Calculator
  ## Examples
    iex> [1,2,3] |> Pmap.calc()
    [1,4,9]

    iex> [1,2,3] |> Pmap.calc(fn(n)-> :math.pow(n,n) |> Kernel.trunc() end)
    [1, 4, 27]
  """


  def calc(arr) do
    arr
    |> Enum.map(&emit(&1, self()))
    |> Enum.map(&listen/1)
  end

  def calc(arr, fun) do
    arr
    |> Enum.map(&emit(&1, self(), fun))
    |> Enum.map(&listen/1)
  end

  def function(n), do: n * n
end