Another update from ingydotnet^djgoku

Task/Range-extraction/Elixir/range-extraction.elixir

@@ -0,0 +1,30 @@
+defmodule RC do
+  def range_extract(list) do
+    max = Enum.max(list) + 2
+    sorted = Enum.sort([max|list])
+    canidate_number = hd(sorted)
+    current_number = hd(sorted)
+    extract(tl(sorted), canidate_number, current_number, [])
+  end
+
+  defp extract([], _, _, range), do: Enum.reverse(range) |> Enum.join(",")
+  defp extract([next|rest], canidate, current, range) when current+1 >= next do
+    extract(rest, canidate, next, range)
+  end
+  defp extract([next|rest], canidate, current, range) when canidate == current do
+    extract(rest, next, next, [to_string(current)|range])
+  end
+  defp extract([next|rest], canidate, current, range) do
+    seperator = if canidate+1 == current, do: ",", else: "-"
+    str = "#{canidate}#{seperator}#{current}"
+    extract(rest, next, next, [str|range])
+  end
+end
+
+list = [
+   0,  1,  2,  4,  6,  7,  8, 11, 12, 14,
+  15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
+  25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
+  37, 38, 39
+]
+IO.inspect RC.range_extract(list)