Re: simplifying following-sibling and preceding-sibling

  Hello Dmitry,

  thank you very much for comments!

On Fri, 14 Jan 2005 17:54:29 +0300
"Dmitry Lizorkin" <[email protected]> wrote:

> Hello!
> 
> Well, with the simplifications you suggested your implementation for
> "sxml:following-sibling" and "sxml:preceding-sibling" calls the child
> axis twice on the parent node of the context node:
>  a) the first time the child axis is called when locating the parent of
>  the
> context node, i.e. in the body of "sxml:parent";
>  b) the second time the child axis is called when you select siblings of
>  the
> context node.
> 
> The "tricky enough code" you mentioned in the implementation for
> following-sibling and preceding-sibling axes provided in
> "sxpath-ext.scm" is designed to eliminate the duplicate call to the
> child axis considered above.

  Thank you for the explanation. I understand how sxml:following-sibling
works in general, but I've missed the elimination trick.

  Anyway, in my case (I hope to make a posting about it soon) I'll use
my variant, slightly modified:

  ...
  ; Get all siblings which are the kids of the parent,
  ; find the node position and filter the rest
  (let* (
      (kids    ((sxml:child  sxml:node?) (nsxml:parent node)))
      (inkids  (memq node kids)))
    (if inkids
      ((sxml:filter test-pred?) (cdr inkids))
      '()))))))

  Usage of "nsxml:parent" is explicit here. The function "nsxml:parent"
stands for "native sxml parent". It knows how to get parents very fast,
and I'd like to exploit it.

...

> 
> Regards,
> Dmitry
>

  Regards, Oleg



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