anchor.diff:  
   (defun sort-stable-demo ()
     (let ((a (map 'vector #'cons
  -                (random-array 10 :bound 5)
  -                (random-array 10 :bound 100))))
  +                (gen-random-vector 10 :bound 5)
  +                (gen-random-vector 10 :bound 100))))
       (flet ((cmp (x y) (< (car x) (car y))))
         (print (sort a #'cmp))
         (print (sort a #'cmp))
  
positive.code:           (ackermann (- m 1) (ackermann m (- n 1))))))
  
  ;; bound should be integer, float, long-float
  (defun random-array (n &key (bound 1.0) (rng *random-state*))
    (let ((a (make-array n)))
      (dotimes (i n)
        (setf (aref a i) (random bound rng)))
      a))
  
  (defun shuffle-array (n)
    (let ((a (make-array n)))
      (dotimes (i n)
        (setf (aref a i) i))
      (dotimes (i n)
        (rotatef (aref a i) (aref a (random n))))
      a))
  
  ;; same as logcount
  (defun count-ones-v1 (n)
  
negative.code:         (t 0)))
  
  (defun test-sum-array (&optional (n 10))
    (let* ((a (gen-random-vector n :bound 100))
           (v (list (sum-array-v0 a)
                    (sum-array-v1 a)
                    (sum-array-v2 a)
  