Conway's Game of Life in Elixir

conway.exs

defmodule ConwayTest do
  use ExUnit.Case

  # The Rules

  # For a space that is 'populated':
  #    Each cell with one or no neighbors dies, as if by solitude.
  #    Each cell with four or more neighbors dies, as if by overpopulation.
  #    Each cell with two or three neighbors survives.
  # For a space that is 'empty' or 'unpopulated'
  #    Each cell with three neighbors becomes populated.


  test "gen_interesting" do
    world = [{1,1}, {1,2}, {1,3}]
    assert world != world |> gen_interesting
    assert world = world |> gen_interesting |> gen_interesting
  end

  def gen_interesting(cells) do
    cfilter = fn ({cell, cnt}) ->
                case cnt do
                  3 -> true
                  2 -> Enum.member?(cells, cell)
                  _ -> false
                end
              end

    cells
    |> Enum.map(&neighbours/1)
    |> Enum.concat
    |> Enum.group_by(&(&1))
    |> Enum.map(fn ({x,xs}) -> {x, Enum.count xs} end)
    |> Enum.filter(cfilter)
    |> Enum.map(fn {x, _} -> x end)
  end

  def neighbours({x,y}) do
    for i <- (-1..1), j <- (-1..1), i != 0 || j != 0, do: {x+i, y+j}
  end
end