Strange `file-name-sans-extension' behavior

[Jens Schmidt]

This bug report will be sent to the Free Software Foundation,
not to your local site managers!
Please write in English, because the Emacs maintainers do not have
translators to read other languages for them.

Your bug report will be posted to the bug-gnu-emacs@gnu.org mailing list,
and to the gnu.emacs.bug news group.

In GNU Emacs 21.1.1 (i386-msvc-nt4.0.1381)
 of 2001-10-22 on buffy

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

(file-name-sans-extension "sys/types.h")

-> "c:/home/jschmidt/sys/types"

I would have expected the result "sys/types".

What about the following version of `file-name-sans-extension':

(defun file-name-sans-extension (filename)
  "Return FILENAME sans final \"extension\".
The extension, in a file name, is the part that follows the last `.'."
  (let ((file (file-name-sans-versions (file-name-nondirectory filename)))
          directory)
      (if (string-match "\\.[^.]*\\'" file)
          (if (setq directory (file-name-directory filename))
              (concat (file-name-as-directory directory)
                      (substring file 0 (match-beginning 0)))
            (substring file 0 (match-beginning 0)))
        filename)))

Regards

Jens