grouping.cl

(defun group-adjacent (list &key (test #'eql))
  ((
    (lambda (group x)
      (if (or (funcall test (car group) x) (funcall test x (car group)))
          (progn
            (push group result)
            (list x))
          (cons x group)))

    (cdr list) 
    :initial-value (list (car list)))
   (nreverse result)))

(defun compare-letters (a b)
  (< (abs a) (abs b)))

(defun total-letters (group)
  (reduce #'+ (mapcar #'signum group)))

(defun sum-distinct (word)
  (reduce #'+
          (mapcar #'abs
                  (mapcar #'total-letters
                          (group-adjacent (sort (copy-list word) #'compare-letters) :test #'compare-letters)))))