 
   defp hex(n) when n <= 9, do: <<n + ?0>>
   defp hex(n) when n > 15 do
-    hex(:erlang.bsr(n, 4)) <> hex(:erlang.band(n, 15))
+    hex(bsr(n, 4)) <> hex(band(n, 15))
   end
   defp hex(n), do: <<n + ?A - 10>>
 

                   fragment: nil, authority: nil,
                   userinfo: nil, host: nil, port: nil,
                   specifics: nil]

  @moduledoc """
  Utilities for working with and creating URIs.

  # to replace those with nil for consistency.
  defp nillify(l) do
    lc s in l do
      if size(s) > 0 do
        s
      else:
        nil
