Christmas Trees in Elixir

xmastree.ex

defmodule Tree do
  def print(n) do
    for i <- 1 .. n do
      p(n - i, " ")
      p(i * 2 - 1, "*")
      w("\n")
    end
    p(n - 1, " ")
    w("|\n")
  end
  defp p(n, x)
  defp p(0, _), do: :ok
  defp p(n, x), do: for _ <- 1 .. n, do: w(x)
  defp w(x), do: IO.write(x)
end

defmodule BloatedTree do
  def print(n) do
    for i <- 1 .. n, do: p(d(n - i, " ") <> d(i * 2 - 1, "*"))
    p(d(n - 1, " ") <> "|")
  end
  defp d(n, s), do: String.duplicate(s, n)
  defp p(x), do: IO.puts(x)
end

defmodule SinglePrintTree do
  def print(n) do
    leaves = for i <- 1 .. n, do: d(n - i, " ") <> d(i * 2 - 1, "*")
    stem = d(n - 1, " ") <> "|"
    IO.puts(Enum.join(leaves ++ [stem], "\n"))
  end
  defp d(n, s), do: String.duplicate(s, n)
end

defmodule SinglePrintIOListTree do
  def print(n) do
    leaves = for i <- 1 .. n, do: [d(n - i, " "), d(i * 2 - 1, "*"), "\n"]
    stem = [d(n - 1, " "), "|"]
    IO.puts [leaves, stem]
  end
  defp d(n, s), do: String.duplicate(s, n)
end

defmodule SinglePrintNoDuplicateIOListTree do
  def print(n) do
    leaves = for i <- 1 .. n, do: [d(n - i, " "), d(i * 2 - 1, "*"), "\n"]
    stem = [d(n - 1, " "), "|"]
    IO.puts [leaves, stem]
  end
  defp d(n, s, a \\ [])
  defp d(0, _, a), do: a
  defp d(n, s, a), do: d(n - 1, s, [s | a])
end

test = fn ->
  for x <- 1 .. 10 do
    {a, _} = :timer.tc(fn ->
      for _ <- 1 .. 1000, do: Tree.print(x)
    end)
    {b, _} = :timer.tc(fn ->
      for _ <- 1 .. 1000, do: BloatedTree.print(x)
    end)
    {c, _} = :timer.tc(fn ->
      for _ <- 1 .. 1000, do: SinglePrintTree.print(x)
    end)
    {d, _} = :timer.tc(fn ->
      for _ <- 1 .. 1000, do: SinglePrintIOListTree.print(x)
    end)
    {e, _} = :timer.tc(fn ->
      for _ <- 1 .. 1000, do: SinglePrintNoDuplicateIOListTree.print(x)
    end)
    {x, a, b, c, d, e}
  end
end

((fn ->
  #
  # With I/O to STDIO
  #
  # [
  #   {1, 12529, 9639, 5628, 4913, 5047},
  #   {2, 40616, 15349, 4672, 5342, 7255},
  #   {3, 86754, 42744, 13583, 15537, 16900},
  #   {4, 179915, 23662, 10248, 6174, 9779},
  #   {5, 199164, 29099, 8647, 6944, 8353},
  #   {6, 275208, 33379, 9747, 7681, 7818},
  #   {7, 373047, 40429, 14440, 11855, 11288},
  #   {8, 532534, 42508, 17121, 31591, 16638},
  #   {9, 566551, 48979, 11900, 21552, 12687},
  #   {10, 723348, 55072, 12314, 24258, 14422}
  # ]
  #
  test.() |> IO.inspect
end).())

((fn ->
  #
  # Without I/O to STDIO via I/O capturing in ExUnit
  #
  # [
  #   {1, 5053, 4624, 3391, 2768, 2130},
  #   {2, 14860, 6711, 3154, 2536, 2491},
  #   {3, 34378, 14339, 6651, 4077, 4985},
  #   {4, 64317, 14771, 5655, 4150, 5587},
  #   {5, 151442, 21348, 7600, 5281, 5953},
  #   {6, 149298, 17912, 6075, 4475, 9791},
  #   {7, 174312, 18847, 6975, 4240, 5562},
  #   {8, 210175, 22379, 7177, 4889, 7097},
  #   {9, 254250, 25438, 9082, 5199, 7628},
  #   {10, 342061, 56717, 18038, 10416, 19400}
  # ]
  #
  {:ok, result_agent} = Agent.start_link(fn -> nil end)
  ExUnit.CaptureIO.capture_io(fn ->
    result = test.()
    Agent.update(result_agent, fn _ -> result end)
  end)
  Agent.get(result_agent, fn x -> x end) |> IO.inspect
end).())