Another update from ingydotnet^djgoku

Task/Langtons-ant/Elixir/langtons-ant.elixir

@@ -0,0 +1,29 @@
+defmodule Langtons do
+  def ant(sizex, sizey) do
+    {px, py} = {div(sizex,2), div(sizey,2)}     # start position
+    move(HashSet.new, sizex, sizey, px, py, {1,0}, 0)
+  end
+
+  defp move(plane, sx, sy, px, py, _, step) when px<0 or sx<px or py<0 or sy<py, do:
+    print(plane, sx, sy, px, py, step)
+  defp move(plane, sx, sy, px, py, dir, step) do
+    {plane2, {dx,dy}} = if Set.member?(plane, {px,py}),
+                          do:   {Set.delete(plane, {px,py}), turn(dir, :right)},
+                          else: {Set.put(plane, {px,py}), turn(dir, :left)}
+    move(plane2, sx, sy, px+dx, py+dy, {dx,dy}, step+1)
+  end
+
+  defp turn({dx, dy}, :right), do: {dy, -dx}
+  defp turn({dx, dy},      _), do: {-dy, dx}
+
+  defp print(plane, sx, sy, px, py, step) do
+    IO.puts "out of bounds after #{step} moves: (#{px}, #{py})"
+    Enum.each(0..sy, fn j ->
+      Enum.map(0..sx, fn i ->
+        if Set.member?(plane, {i,j}), do: "#", else: "."
+      end) |> Enum.join |> IO.puts
+    end)
+  end
+end
+
+Langtons.ant(100, 100)