anchor.diff:                do (let ((gesture (buffer-object buffer scan-pointer)))
                      ;; Skip noise strings.
                      (cond ((typep gesture 'noise-string)
  -                          (incf scan-pointer))
  +                          (incf scan-pointer)
  +                          (setf last-was-noisy t))
                            ((and (not peek-p)
                                  (typep gesture 'accept-result))
                             (incf scan-pointer)
  
positive.code:     (with-accessors ((insertion-pointer stream-insertion-pointer)
                       (scan-pointer stream-scan-pointer)
                       (activation-gesture activation-gesture)) stream
        (let ((buffer (buffer (view (drei-instance stream)))))
          (loop
             (loop
                while (< scan-pointer insertion-pointer)
  
negative.code:                           (unless peek-p
                              (incf scan-pointer))
                            (return-from stream-read-gesture gesture))
                           (t (incf scan-pointer)
                              (setf last-was-noisy nil)))))
             (unless last-was-noisy ; This prevents double-prompting.
               (setf (stream-rescanning stream) nil))
             (when activation-gesture
               (return-from stream-read-gesture
                 (prog1 activation-gesture
  