xyzzy: replace '/' <--> '\' at current line (for path string win and linux)

discrete.l

(defun slash-to-backslash-line ()
  "replace '/' <--> '\' at current line. (toggle)"
  (interactive)
  (save-excursion
    (let ((eol (progn (goto-eol) (point)))
          (bol (progn (goto-bol) (point))))
      (save-restriction
        (narrow-to-region bol eol)
        (let (from to)
          (cond ((looking-for "\\") (setq from "\\")
                                    (setq to "/"))
                ((looking-for "/")  (setq from "/")
                                    (setq to "\\")))
          (when from
              (replace-buffer from to)))))))