Sort filenames in a natural way

fnsorter.rb

# convert a filename into an array suitable for sorting
def filename_to_sortable(fn)
  # convert numeric parts of the string given into actual numbers.
  # Keep a string (third element) to disambiguate
  fn.scan(/(\D*)(\d*)/).map{ |alpha, numeric| [alpha, numeric.to_i, numeric]}
end

# sort filenames in a "natural" way, keeping numeric parts ascending numerically
def sort_filenames(a)
  a.sort_by{ |fn| filename_to_sortable(fn) }
end

if __FILE__ == $0
 require 'test/unit'

 class FNS_MyTest < Test::Unit::TestCase
   def test_single
     assert_equal(["1", "2"], sort_filenames(["1", "2"]))
   end
   def test_numeric_normal
     assert_equal(["2", "18"], sort_filenames(["2", "18"]))
   end
   def test_numeric_inverse
     assert_equal(["18", "123"], sort_filenames(["123", "18"]))
   end
   def test_num_to_alpha
     assert_equal(["18", "a123"], sort_filenames(["a123", "18"]))
   end
   def test_alpha_simple_alpha
     assert_equal(["a18a", "a123a"], sort_filenames(["a123a", "a18a"]))
   end
   def test_alpha_diff_simple_alpha
     assert_equal(["a123a", "b18a"], sort_filenames(["a123a", "b18a"]))
   end
   def test_simple_alpha
     assert_equal(["18a", "123a"], sort_filenames(["123a", "18a"]))
   end
   def test_simple_alpha_diff
     assert_equal(["18b", "123a"], sort_filenames(["123a", "18b"]))
   end
   def test_disambiguate
     assert_equal(["a01a", "a1a", "a02a", "a2a"], sort_filenames(["a1a", "a01a", "a2a", "a02a"]))
   end
   def test_real
     sorted = %w(
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)
     assert_equal(sorted, sort_filenames(sorted.shuffle))
   end

 end
end