Function call expecting list works with a tuple

donnieparka
Wed, 22 Jan 2025 12:01:14 +0000
Questions / Help

defmodule Navigator do
  def navigate(dir) do
    expanded_dir = Path.expand(dir)

    go_through([expanded_dir])
  end

  def go_through([]), do: nil

  def go_through([content | rest]) do
    print_and_navigate(content, File.dir?(content))

    go_through(rest)
  end

  def print_and_navigate(_dir, false), do: nil

  def print_and_navigate(dir, true) do
    IO.puts(dir)

    children_dirs = File.ls!(dir)

    go_through(expand_dirs(children_dirs, dir))
  end

  def expand_dirs([], relativeto), do: []

  def expand_dirs([dir | dirs], relative_to) do
    expanded_dir = Path.expand(dir, relative_to)

    [expanded_dir | expand_dirs(dirs, relative_to)]
  end
end

in:

def print_and_navigate(dir, true) do
   IO.puts(dir)

   children_dirs = File.ls!(dir)

   go_through(expand_dirs(children_dirs, dir))
 end

children_dirs is a tuple and expand_dirs expects a list so why do i not get an error? do functions pattern match incoming arguments before throwing errors of arguments compatibility? where can i read more about where and when pattern matching happens?

8 posts - 3 participants