Re: chains of SXML transformations?

Hi,

Oleg wrote:
>The problem can be rectified, by changing pre-post-order as shown in
>the appendix. [...] This operation seems to make sure
>that each node of a tree is an SXML node. 

That's it!!! it's much cleaner than an a posteriori pass through the output, trying to remove superfluous nesting. Great solution!

Having the handlers during processing already see proper SXML is a clear improvement, which allows easier macros, e.g. a reliable "first" transfomer
 (first . ,(lambda (tag . elems) (first elems)))
; because elems is a proper SXML node/list
; ignore attributes (@)


Your solution is not 100% right, though (ah, those nasty border cases):
(define identity-transforms
  ;; A string is seen converted to (*text* string) by pre-post-order
  `((*default* . ,(lambda x x))
    (*text*    . ,(lambda (trigger str) str))))
(pre-post-order-proper '(Request (Prio 1) (stuff 3))
 (append
  `((Prio *macro* . ,(lambda x '()))
    ) identity-transforms))
-> (Request () (stuff 3))
ought to be: (Request (stuff 3)) for proper SXML.


>For a pure SXML-to-XML conversion, the splicing-in seems to be an
>overkill.
Indeed, SXML->X|HT|ML doesn't need it. It has proven useful so far.

Thank you very much again!
	Jorg Hohle.


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