anchor.diff:    (setf a 100)
     (setf b 23)
     (setf c 456)
  -  (let ((a 0)
  -        (b __)
  -        (c __))
  +  (let ((a 100)
  +        (b 200)
  +        (c "Jellyfish"))
       (assert-equal a 100)
       (assert-equal b 200)
       (assert-equal c "Jellyfish"))
  
positive.code: 
  (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 
       the implications of this in the equality-distinctions lesson"
    (let* ((name "John")
           (lastname (case name ("John" "Doe")
  
negative.code:   (setf a 100)
    (let ((a 5)
          (b (* 10 a)))
      (assert-equal b 50)))
  
  (define-test test-let*-bindings-are-series
      "let* is like let, but successive bindings may use values of previous ones"
    (setf a 100)
    (let* ((a 5)
           (b (* 10 a)))
      (assert-equal b 50))
    (assert-equal a 100))
  
  
  (define-test write-your-own-let-statement
  