Here’s another option!

  def segment_path(path) when is_binary(path) do
    segments = String.split(path, "/", trim: true)

    paths =
      Enum.reduce(segments, [], fn
        segment, [] -> ["/#{segment}"]
        segment, [head | _tail] = whole -> ["#{head}/#{segment}" | whole]
      end)

    Enum.zip(segments, Enum.reverse(paths))
  end
end

What makes this more readable IMHO:

• Fewer LOC
• Contained in one function which tells me a clear story
• Building the paths as we move forward in a visually clear way with interpolation rather than list |> Enum.reverse() |> Enum.join()
• Only reversing one list at the end
• Using Enum.reduce/3 which is very familiar to most Elixir devs

You can of course pipe the reduce block into Enum.reverse() instead of inlining it in the zip call, if that’s your preference

As an added bonus this implementation benchmarks 20% faster on my machine than your original

Another way:

def segment_path(path) do
  path_levels =
    path
    |> String.split("/", trim: true)
    |> length()

  path
  |> breadcrumb()
  |> Stream.iterate(fn
    {segment, segment_path} ->
      parent_path = String.replace_trailing(segment_path, "/#{segment}", "")
      breadcrumb(parent_path)
  end)
  |> Enum.take(path_levels)
  |> Enum.reverse()
end

def breadcrumb(path) do
  segment = path
  |> String.split("/")
  |> List.last()

  {segment, path}
end

The solution with this code unfolds like this:

path = "/some/path/to/nowhere"

1. {"nowhere", "/some/path/to/nowhere"}
2. {"to", "/some/path/to"}
3. {"path", "/some/path"}
4. {"some", "/some"}

Then it’s reversed.

I won’t add reasoning on why (or whether) this is better, but just another implementation.

Hopefully this is at least par for the course . @Ninigi I’m interested in what you’d use instead of do_ here.

defmodule Example do
  def segment_path(path) do
    path |> String.split("/", trim: true) |> do_segment_path("")
  end

  defp do_segment_path([], _path), do: []

  defp do_segment_path([current | rest], path) do
    new_path = "#{path}/#{current}"
    [{current, new_path} | do_segment_path(rest, new_path)]
  end
end

Running:

iex(1)> Example.segment_path("path/to/segment")
[{"path", "/path"}, {"to", "/path/to"}, {"segment", "/path/to/segment"}]