anchor.diff:  
   
   (defun vowelp (c)
  -  "returns true iff c is a vowel"
  +  "returns true if c is a vowel"
     (find c "AEIOUaeiou"))
   
   (defun vowels-to-xs (my-string)
  
positive.code:     (assert-equal ___ how-many-in-list)
      (assert-equal ___ biggest-in-list))
    (let ((sum 0))
      "write your own do-list here to calculate the sum of some-primes"
      "you may be interested in investigating the 'incf' function"
      ;(dolist ... )
      (assert-equal 999607602 sum)))
  
negative.code:       variable in turn"
    (let ((how-many-in-list 0)
          (biggest-in-list (first some-primes)))
      "this dolist loops over some-primes, defined above"
      (dolist (one-prime some-primes)
        (if (> one-prime biggest-in-list)
            (setf biggest-in-list one-prime))
  