Future experiments from Elixir meetup

future.ex

defmodule Future do
  def new(fun) do
    fn(x) ->
          spawn_link fn ->
            value = try do
              { :ok, fun.(x) }  
            rescue
              e -> { :error, e }
            end

            receive do 
              pid -> 
                pid <- {self, value} 
            end
          end
    end 
  end

  def value(pid, timeout // :infinity, default // {:error, :timeout}) do
      pid <- self
      receive do
          {^pid, {:ok, value}} -> value
          {^pid, {:error, e}}  -> raise e
      after 
          timeout -> default
      end 
  end
end

defmodule Parallel do
  def pmap(collection, fun) do 
    collection
    |> Enum.map(Future.new(fun))
    |> Enum.map(Future.value(&1, 1000, {:error}))
  end
end

IO.inspect Parallel.pmap([1,2,3,4], fn x -> :timer.sleep(1000); x+1 end)