:UP vs. :BACK

In LWW 5.0.1 I see this behaviour:

  CL-USER 18 > (truename
                (make-pathname :name "app" 
                               :type "lisp"
                               :directory '(:absolute "tmp" :up "tmp")))
  #P"c:/tmp/../tmp/app.lisp"

  CL-USER 19 > (truename
                (make-pathname :name "app"
                               :type "lisp"
                               :directory '(:absolute "tmp" :back "tmp")))
  #P"c:/tmp/app.lisp"

If I understand 19.2.2.4.3 correctly (none of the directories involved
has multiple names), the results should be EQUAL, but they aren't.

So, is this a bug or am I missing something?

Re: :UP vs. :BACK

On Sun, 25 Mar 2007 19:59:38 -0400, Gary King <gwking@metabang.com> wrote:

> I would think that :up and :back could differ in the case of
> symbolic links (I haven't tried this yet)

Sure.  That's why I said none of the directories involved has multiple
names.

Re: :UP vs. :BACK

On 25 Mar 2007, at 23:13, Edi Weitz wrote:

> If I understand 19.2.2.4.3 correctly (none of the directories involved
> has multiple names), the results should be EQUAL, but they aren't.

I don't think I can think of a case where TRUENAME on a Unixoid FS  
would involve path components named "..", since there is always a  
better canonical name for any file, and TRUENAME is meant to find that.

>
> So, is this a bug or am I missing something?

I think it is.