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

[Dave Love <d.love@dl.ac.uk>]

>>>>> "PJ" == Paul Jarc <prj@po.cwru.edu> writes:

 PJ> It depends on the contents of "file-name".  If it might contain
 PJ> something that really needs to be normalized, then it should be
 PJ> handed to expand-file-name.  If it should be interpreted
 PJ> literally, then expand-file-name might do something unintended.
 PJ> Consider, e.g., "foo/../bar", where foo is a symlink.

I don't understand this.  One of the points about expand-file-name is
that it gets to do magic depending on the file name.  I have changed
such uses of `concat' where I've found it in the sources and I'd need
some convincing that that's wrong, as well as a contribution to the
Lisp manual.

 PJ> I think file-name-as-directory and directory-file-name are
 PJ> idempotent on all platforms, although they aren't documented as
 PJ> such, AFAICT.

I'm not sure why that's relevant, but even if it's generally true in
the absence of handlers -- I don't know -- I don't think you can say
what a random handler might do, e.g. for remote files on an arbitrary
system.