anchor.diff:    (let ((x 0)
           (y 0))
       (double-setf-BAD x y (+ x 100))
  -    (assert-equal x ____)
  -    (assert-equal y ____)))
  +    (assert-equal x 100)
  +    (assert-equal y 200)))
   
   ;; sets sym1 and sym2 to val
   (defmacro double-setf-SAFER (sym1 sym2 val)
  
positive.code:    to the list *log-with-value* and then evalues the body normally"
    `(let ((logform nil)
           (retval ,form))
  
       ;; YOUR MACRO COMPLETION CODE GOES HERE.
  
       retval))
  
  
  
negative.code:   (let ((x 0)
          (y 0))
      (double-setf-SAFER x y (+ x 100))
      (assert-equal x 100)
      (assert-equal y 100)))
  
  
  ;; ----
  