(defstruct range-details feature range size details)

(defun splitter (x &key
                 baseline 
                 detail
                 debug
                 (compare  #'-)            
                 (overall  #'range-details-weighted-sum))
  (let (best
        (max -1)
        (classi (xindex-classi x))
        (before (funcall baseline x)))
    (dotimes (feature (xindex-width x) best)
      (unless (= feature classi)
        (let* ((after
                (range-details-all feature x
                                   :detail detail
                                   :overall overall))
              (delta (funcall compare before after)))
          (if debug (o feature delta))
          (if (> delta max)
              (setf max delta
                    best feature )))))))
         
(defun range-details-all (feature x &key detail overall)
  (let ((details (mapcar #'(lambda(range)
                             (range-details-one feature range x detail))
                         (xindex-feature feature x))))
    (funcall overall details feature x)))

(defun range-details-one (feature range x detail)
  "collect information on one range"
  (let ((n  (xindex-unique-n x feature range )))
    (make-range-details
     :feature feature
     :range range
     :size  n
     :details (funcall detail feature range n x))))

(defun range-details-weighted-sum (details feature x)
  "return the weighted sum of the details weighted sum"
  (let* ((total 0)
         (weights (mapcar #'(lambda (d)
                              (let ((tmp (range-details-size d)))
                                (incf total tmp)
                                (cons tmp
                                      (range-details-details d))))
                         details)))
    (weighted-sum weights total)))