anchor.diff:      "mapcar and reduce are a powerful combination.
        insert the correct function names, instead of WRONG-FUNCTION-X
        to define an inner product."
  -  (defun inner (x y) 
  +  (defun inner (x y)
       (reduce #'WRONG-FUNCTION-2 (mapcar #'WRONG-FUNCTION-3 x y)))
     (assert-equal 32 (inner '(1 2 3) '(4 5 6)))
     (assert-equal 310 (inner '(10 20 30) '(4 3 7))))
  
positive.code:     "We can apply a function to each member
       of a list using mapcar."
    (defun times-two (x) (* x 2))
    (assert-equal ____ (mapcar #'times-two '(1 2 3)))
    (assert-equal ____ (mapcar #'first '((3 2 1) 
                                        ("little" "small" "tiny") 
                                        ("pigs" "hogs" "swine")))))
  
  
  
negative.code:   (defun WRONG-FUNCTION-1 (&rest rest) '())
    (defun transpose (L) (apply #'mapcar (cons #'WRONG-FUNCTION-1 L)))
    (assert-equal '((1 4 7)
                    (2 5 8)
                    (3 6 9))
                  (transpose '((1 2 3)
                               (4 5 6)
                               (7 8 9))))
    (assert-equal '(("these" "pretzels" "are")
                    ("making" "me" "thirsty"))
  