anchor.diff:  
   (define-test test-limits-of-case
       "case is not suitable for all kinds of values, because
  -     it uses the function eql for comparisons. We will explore 
  +     it uses the function eql for comparisons. We will explore
        the implications of this in the equality-distinctions lesson"
     (let* ((name "John")
            (lastname (case name ("John" "Doe")
  
positive.code:     "setf is used to assign values to symbols.  These symbols may refer to
       variables with lexical or dynamic scope."
    (setf my-name "David")
    (assert-equal my-name ____)
    " In SBCL, if the symbol isn't defined as a variable, via a top-level defvar
    or let statement, the setf call may result in a warning."
    (setf my-clones-name my-name)
    (assert-equal "David" ____)
    (setf a 5)
    (setf b 10)
    (setf c ___)
    (assert-equal 50 c))
  
  
  
negative.code:   (setf a 100)
    (setf b 23)
    (setf c 456)
    (let ((a 100)
          (b 200)
          (c "Jellyfish"))
      (assert-equal a 100)
      (assert-equal b 200)
      (assert-equal c "Jellyfish"))
  