anchor.diff:                  vm
                   "A user-defined primitive returned an unknown second value.")))
         (when should-finish-this-call
  -        (finish-primitive-call vm num-args result save-return-address)))))
  -
  -(defun finish-primitive-call (vm num-args result save-return-address)
  +        (finish-primitive-call vm result 
  +                               save-return-address new-stack)))))
  +
  +(defun finish-primitive-call (vm result save-return-address new-stack)
     (declare (optimize speed (safety 0)))
  -  (setf (vm-stack vm) (nthcdr num-args (vm-stack vm)))
  +  (setf (vm-stack vm) new-stack)
     (if save-return-address
         (incf (the fixnum (vm-program-counter vm)))
         (apply-return-address vm (pop (vm-stack vm))))
  
positive.code: (defun reversed-prefix (list n &optional acc)
    (declare (optimize speed (safety 0))
             (type fixnum n))
    (if (= n 0) acc
        (reversed-prefix (rest list) (1- n) (cons (first list) acc))))
  
  (defun finish-calling-required-primitive (primitive arg-values num-args save-return-address vm)
    (let ((result (apply primitive arg-values)))
      (finish-primitive-call vm num-args result save-return-address)))
  
  (defun finish-calling-user-defined-primitive (primitive arg-values num-args
                                                current-program-counter callable
                                                save-return-address
                                                vm)
    (multiple-value-bind(result what-next)
        (handler-case
  
negative.code:               expected-arity actual-arity)))
  
  (defun call-function (callable vm num-args save-return-address)
    (declare (optimize speed (safety 0)))
    (when save-return-address
      (push (make-return-address :program-counter (the fixnum (1+ (the fixnum (vm-program-counter vm))))
                                 :environment (vm-current-environment vm))
            (vm-stack vm)))
    (when (and (callable-num-args callable)
               (/= (the fixnum (callable-num-args callable))
                   (the fixnum num-args)))
      (arity-error vm (callable-num-args callable) num-args))
    (setf (vm-program-counter vm) (callable-program-counter callable)
          (vm-current-environment vm) (callable-environment callable)))
  