Re: (concat "/dir/name/" "foo") --> (expand-file-name "foo" "/dir/name/")

[Kai.Grossjohann@CS.Uni-Dortmund.DE (Kai Großjohann)]

On 22 Oct 2000, Paul Jarc wrote:
> Kai.Grossjohann@CS.Uni-Dortmund.DE (Kai Großjohann) writes:
>> I have tried hard to come up with a reason why expand-file-name
>> could fail to be idempotent, but I can't come up with a reason.
> 
> A mischevious, badly-written, or maybe just an unconventional
> handler might give an expanded name that would, when re-expanded,
> give a different name.  But this probably doesn't happen in most
> normal situations.

So it's a bug when expand-file-name fails to be idempotent?  (What's
the opposite of idempotent?  Idemimpotent?)

>> But in any case, using concat to create a file name from a
>> directory and a relative path name is not a good thing, I think.
> 
> Why not?

Hm.  Maybe it isn't too bad after all, but one has to be very careful
to say (concat (file-name-as-directory D) F), not just (concat D F).
But I think you were saying that file-name-as-directory might not be
idempotent, either, right?  So we have just shifted the problem.

kai
-- 
I like BOTH kinds of music.