Re: Problems with xml-parse-string

[Chong Yidong]

Lars Magne Ingebrigtsen <address@hidden> writes:

> Here's a pretty piece of code, chosen at random:
>
> (defun nnrss-find-el (tag data &optional found-list)
> ...
> The horror!

I think that code might just be crufty.  Here's an implementation,
assuming sxml format:

  (defun nnrss-find-el (tag data &optional found-list)
   "Find the all matching elements in the data.
  Careful with this on large documents!"
   (nreverse (nnrss-find-el-1 tag data)))

  (defun nnrss-find-el-1 (tag data &optional found-list)
    (and (consp data)
         (not (eq (car data) '@))
         (if (equal tag (car data))
             (push data found-list)
           (dolist (bit (cdr data))
             (setq found-list
                   (nnrss-find-el-1 tag bit found-list)))))
    found-list)

Doesn't seem too horrific.  Here's the example tree:

  (setq test-sxml-tree
        '(tag (@ (attr1 "value1")
                 (attr2 "value2"))
              "Free text"
              (foo "Text node 1")
              (bar "Text node 2")
              (baz
                "More free text"
                (foo "Text node 3")
                (bar "Text node 4"))))

> To take a concrete example: You want the src of the img node you have.
>
> xml.el:  (cdr (assq 'img (cadr node)))
> sxml.el: (if (and (consp (cadr node))
>                   (eq (caadr node) '@))
>              (cadr (assq 'img node)))
>
> (And I'm not even sure that's correct.  It's probably not.  Which is my
> point.)
>
> libxml: (cdr (assq :img (cdr node)))
>
> (The difference between libxml and xml.c for attributes is minuscule.)

I think this example is confused.  If you're scanning at top-level,
without descent, the code for all three cases is practically identical:
it's a simple assq.