How to flatten a map?

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6

Here is a slightly simpler implementation that you may be able to evaluate more easily:

defmodule Foo do

  def flatten_map(map) when is_map(map) do
    map
    |> Map.to_list
    |> do_flatten([])
    |> Map.new
  end

  defp do_flatten([], acc), do: acc

  defp do_flatten([{_k, v} | rest], acc) when is_map(v) do
    v = Map.to_list(v)
    flattened_subtree = do_flatten(v, acc)
    do_flatten(flattened_subtree ++ rest, acc)
  end

  defp do_flatten([kv | rest], acc) do
    do_flatten(rest, [kv | acc])
  end
end
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