Flatten implementation written in elixir without language helpers functions

readme.md

Flatten elixir implementation

This script to be executed requires elixir to be installed

To run this script execute $ elixir flatten.exs

The output should be something like this:

$ elixir flatten.exs
.

Finished in 0.02 seconds (0.02s on load, 0.00s on tests)
1 test, 0 failures

flatten.exs

defmodule Flatten do
  @moduledoc """
    List flatten recursive implementation without language helpers
  """

  @doc """
  Flat a nested list of list.

  Returns list flattend.

  ## Examples

    iex> Flatten.flatten([1,[2],[3,4]])
    [1, 2, 3, 4]

  """
  def flatten(list) do
    flatten(list, []) |> reverse([])
  end


  def flatten([], accum), do: accum
  def flatten([[]| tail], accum), do: flatten(tail, accum)
  def flatten([[_|_] = head|tail], accum), do: flatten(tail, flatten(head, accum))
  def flatten([head|tail], accum), do: flatten(tail, [head | accum])

  def reverse([], accum), do: accum
  def reverse([head | tail], accum), do: reverse(tail, [head | accum])
end


ExUnit.start()

defmodule FlattenTest do
  use ExUnit.Case

  setup do
    list_to_flatten = [
      [1, [2], [3, 4]],
      [[1, 2], [3], 4],
      [1, 2, 3, [4]],
      [[1], [2], [3], [4]],
      [[1], 2, 3, [4]],
      [1, [2, 3], 4],
      [[1, 2, 3], [4]],
      [1, 2, [3, 4]],
      [[1, 2], [3, 4]],
      [[1], 2, 3, 4],
      [[1, 2, 3, 4]],
      [[1], [2, 3, 4]]
    ]
    [list_to_flatten: list_to_flatten]
  end
  test "Flatten a list of list", context do
    Enum.each(context[:list_to_flatten], fn(list) ->
     assert Flatten.flatten(list) == [1, 2, 3, 4]
    end)
  end
end