(defun range-extract (numbers)
  `@{(mapcar [iff [callf > length (ret 2)]
                  (ret `@[@1 0]-@[@1 -1]`)
                  (ret `@{@1 ","}`)]
             (mapcar (op mapcar car)
                     (split [window-map 1 :reflect
                                        (op list @2 (- @2 @1))
                                        (sort (uniq numbers))]
                            (op where [chain second (op < 1)])))) ","}`)