Benchmarking /r/elixir/comments/f4z9gn/evenodd_indexes/

benchmark.exs

defmodule Aseigo do
  def split_even_odd_index(list) do
    split_even_odd_index(list, true, {[], []})
  end

  defp split_even_odd_index([], _even_odd, result), do: result

  defp split_even_odd_index([head | tail], true, {evens, odds}) do
    split_even_odd_index(tail, false, {[head | evens], odds})
  end

  defp split_even_odd_index([head | tail], false, {evens, odds}) do
    split_even_odd_index(tail, true, {evens, [head | odds]})
  end
end

Benchee.run(
  %{
    "conrad" => fn list ->
      result_odd_index = Enum.drop_every(list, 2)
      {list -- result_odd_index, result_odd_index}
    end,
    "newking34_v1" => fn list ->
      list
      |> Stream.with_index()
      |> Enum.reduce([[], []], fn {x, i}, [evens, odds] ->
        case rem(i, 2) do
          0 -> [evens ++ [x], odds]
          _ -> [evens, odds ++ [x]]
        end
      end)
    end,
    "newking34_v2" => fn list ->
      %{even: even, odd: odd} =
        list
        |> Enum.with_index()
        |> Enum.group_by(
          fn
            {_n, idx} when rem(idx, 2) == 0 -> :even
            _ -> :odd
          end,
          fn {n, _idx} -> n end
        )
    end,
    "aseigo" => fn list ->
      Aseigo.split_even_odd_index(list)
    end
  },
  inputs: %{
    "scaled2good" => [99, 99, 99, 99, 99],
    "generated" => Enum.to_list(1..10_000),
    "duplicated" => [0, 1, 1, 2, 2, 3, 4, 5]
  },
  print: [fast_warning: false]
)