file-relative-name相当…のつもり #xyzzy

relative-pathnames.lisp

(defun relative-pathnames (fn dir)
  "dirを基準にしたfnの相対パスを返す"
  (if (string-equal (pathname-device #0=(merge-pathnames fn))
                    (pathname-device #1=(merge-pathnames dir)))
      (let ((fn (split-string #0# #\/))
            (dir (split-string #1# #\/)))
        (dotimes (i (length fn))
          (unless (string-equal (nth i fn) (nth i dir))
            (return (format nil "~{~A/~}~{~A/~}~{~A~}"
                            (make-list (- (length dir) i) :initial-element "..")
                            (butlast (last fn (- (length fn) i)))
                            (last fn))))))
    #0#))

間違いなく車輪の再発明…だと思う('A

truename だと存在しないパスの場合エラーが出ちゃうわ…