anchor.diff:  (defun make-vars (x) :hidden
     (if (list? x) x (list x)))
   
  -(defun make-test (x) :hidden
  +(defun make-var (x) :hidden
     (if (list? x) (car x) x))
   
   (defun make-binding (xs) :hidden
  
positive.code: 
     When `bar` has an index `baz`, it will be bound to `foo` and
     printed. If not, the print statement will not be executed."
    `((lambda ,(make-vars (car var)) (when ,(make-test (car var)) ,@body)) ,(cadr var)))
  
  (defun make-setting (var) :hidden
    (if (= (n var) 2)
  
negative.code:      (when (and ,@(cars vars)) ,@body))
      ,@(map make-let-binding vars)))
  
  (defmacro when-let* (vars &body)
    "Bind each pair of `(name value)` of VARS, checking if the value is
     truthy before binding the next, and finally evaluating BODY. As with
  