Playing with concurrency in Elixir

concurrent.ex

defmodule Math do
  @doc """
  Calculate the square of a integer

  This function simualtes an expensive operation by sleeping for x seconds
  """
  def square(x) when is_integer(x) do
    Process.sleep(x * 1_000)
    x * x
  end
end

defmodule English do
  @doc """
  Pluralise a word

  This function simulates and expensive operation by sleeping for the length of the word in seconds

  eg. Given "bat" this function will sleep for three seconds 
  """
  def pluralise(word) when is_binary(word) do
    Process.sleep(String.length(word) * 1_000)
    word <> "s"
  end
end

defmodule Concurrent do
  @doc """
  Execute func for each element in the list concurrently
  """
  def execute(list, func) when is_function(func) do
    pid = self()
    # Enumerate through indexed list and execute func in seperate process
    Enum.each(Enum.with_index(list), fn {x, index} ->
     # Perform work in seperate process
     spawn fn ->
       send pid, {index, func.(x)}
     end
    end)
    collect(Enum.count(list))
  end

  @doc """
  Collect results from workers via the mailbox

  When the number of results is equal to the number of items in the original list return the results

  Results need to be sorted and then the data structure
  """
  defp collect(return_count, results \\ []) when is_integer(return_count) do
    if Enum.count(results) >= return_count do
      Enum.sort(results)
      |> Enum.map(fn {_index, result} -> result end)
    else
      receive do
        result -> collect(return_count, [result | results])
      end
    end
  end
end