Re: Desperate Questions: [1]Absolute-Child-Number

[David Megginson <dmeggins@xxxxxxxxxx>]

W. Eliot Kimber writes:

 > I need the ordinal position of %element%'s parent within the children
 > property of its parent.

If you have an implementation of ipreced already, this is quite easy
to do:

  (define (absolute-child-number snl)
    (if (absolute-first-sibling? snl)
	1
	(+ 1 (absolute-child-number (ipreced snl)))))

Love that tail recursion!  Jade does not yet have ipreced, but I seem
to remember seeing an implementation posted to this list before.  If
not, here's the sample definition from the DSSSL standard:

  (define (ipreced nl)
    (node-list-map (lambda (snl)
		     (let loop ((prev (empty-node-list))
				(rest (siblings snl)))
		       (cond ((node-list-empty? rest)
			      (empty-node-list))
			     ((node-list=? (node-list-first rest) snl)
			      prev)
			     (else
			      (loop (node-list-first rest)
				    (node-list-rest rest))))))
		   nl))

Now, however, you're missing an implementation of siblings.  Here's a
semi-broken one -- the result of over two seconds' though and perhaps
twice as long spent typing -- that will work only with elements (and
not the root element, at that):

  (define (siblings snl)
    (children (parent snl)))


All the best,


David

-- 
David Megginson                 ak117@xxxxxxxxxxxxxxxxxxx
Microstar Software Ltd.         dmeggins@xxxxxxxxxxxxx
University of Ottawa            dmeggins@xxxxxxxxxx
        http://www.uottawa.ca/~dmeggins

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