Re: Emacs 21 and w3 on Debian

[Kevin Rodgers <ihs_4664@yahoo.com>]

Klaus Straubinger wrote:
 > Kevin Rodgers <ihs_4664@yahoo.com> wrote:
 >>How exactly is that improvement implemented?
 >>
 >>(cons redirect-uri url-callback-arguments)
 >>
 >>(if url-callback-arguments
 >>     (cons redirect-uri (cdr url-callback-arguments))
 >>   (list redirect-uri))
 >
 > I chose something like the second alternative:
 >
 >   (if url-callback-arguments
 >       (setcar url-callback-arguments redirect-uri)
 >     (setq url-callback-arguments (list redirect-uri)))

Is it necessary to destructively modify url-callback-arguments?  I.e.
is it used elsewhere that must reflect the redirection as well?

Note that setcar does not return the modified cons, so I think that
should be (asssuming setcar is indeed necessary):

   (if url-callback-arguments
       (progn
         (setcar url-callback-arguments redirect-uri)
         url-callback-arguments)
     (setq url-callback-arguments (list redirect-uri)))

 > The first would not be correct because the URL sometimes already
 > present as first argument in the url-callback-arguments list must be
 > replaced.

Again: destructively, or just in this particular call to url-retrieve?

 > Would it work then to simply write
 >
 >   (setq url-callback-arguments
 >           (append (list redirect-uri) (cdr url-callback-arguments)))
 >
 > independent of the value of url-callback-arguments?

Yes, it's not necessary to test url-callback-arguments and it's better
to avoid destructive operations on lists unless you're sure of what
you're doing.

But (append (list x) ...) is better expressed as (cons x ...):

   (cons redirect-uri (cdr url-callback-arguments))

Again, why setq?  Do you really need to change its global value?

-- 
Kevin Rodgers