anchor.diff:  (defun skip-expr-prefix-forward (line-buffer point)
     (skip-forward line-buffer point #'expr-prefix-char-p))
   
  -(defun skip-list-forward (line-buffer point)
  -  (loop :with depth := 0 :do
  +(defun skip-list-forward (line-buffer point &optional (depth 0))
  +  (loop
       (incf point)
       (when (<= (length line-buffer) point)
  -      (return (length line-buffer)))
  +      (throw 'scan-error nil))
       (case (forward-syntax-type line-buffer point)
         ((:open-paren)
          (incf depth))
  
positive.code: 
  (defun backward-sexp-point (line-buffer point)
    (setq point (skip-space-backward line-buffer point))
    (skip-sexp-backward line-buffer point))
  
  (defun backward-sexp (arg key)
    (setq rl:*point*
  
negative.code: (defun skip-expr-prefix-backward (line-buffer point)
    (skip-backward line-buffer point #'expr-prefix-char-p))
  
  (defun skip-list-backward (line-buffer point &optional (depth 0))
    (loop
      (decf point)
      (when (<= point 0)
        (throw 'scan-error nil))
      (case (backward-syntax-type line-buffer point)
        ((:closed-paren)
         (incf depth))
        ((:open-paren)
         (when (minusp (decf depth))
           (return (1- point))))
        ((:string-quote)
         (setq point (skip-string-backward line-buffer point))))))
  