(defun freq-list (alist &optional (num.bins 10))
  "Given a list of numbers, count frequencies."
  (let* ((slist (sort (copy-list alist) #'<))
	 (size (/ (- (car (last slist))
		     (first slist))
		  num.bins))
	 (max (first slist))
	 (al nil)
	 (at 0)
	 (curr 0)
	 (next 1))
    (dotimes (i num.bins)
      (setf al (append al (list `(,max . 0))))
      (setf max (+ max size)))
    (setf curr (car (nth at al))
	  next (car (nth (+ at 1) al)))
    (dolist (item slist)
      (if (not (<= curr item next))
	  (progn
	    (setf at 0)
	    (dolist (bin al)
	      (if (< (car bin) item)
		  (incf at)))
	    (if (< (+ at 1) num.bins)
		(progn
		  (setf curr (car (nth at al))
			next (car (nth (+ at 1) al))))
		(setf curr (car (nth (- at 1) al))
		      next most-positive-fixnum))))
      (setf (cdr (assoc curr al)) (+ (cdr (assoc curr al)) 1)))
    al))

(defun demo-freq-list ()
  (freq-list '(4 3 56 2 3 4 7 15 32 4 25 25 25 25 25)))