XPath predicate in with-param's select

Hi,

   I'm trying to implement a fold "function" using XSLT. My current
attempt can be found here:
http://pastebin.com/m2334c86a

The code runs fine as is. But the processing time explodes (from 6s to
82m) if I change line 33 such that the select statement uses a
predicate on the node set. The comment at the end of the line includes
the predicate that I'd like to use. I'm trying to pass the "current"
node to the helping function. Please note that the current helping
function does not use the param for any kind of computation. A similar
problem (time wise) occurs if I try to shrink the node set that is
passed around in line 45, using a predicate such as
$node_set[position() > 1]. Wouldn't this be better practice? Or is
evaluating the predicate on a large node set (~10000) more expensive?

I'm using 4Suite's 1.0.2 4xslt and Python 2.5.1. Please let me know if
any further information would be of help.

Any hint as to why this is happening and how I could fix it would be
greatly appreciated.

I already posted this question on 4Suite's mailing list as I'm hoping
that I would get feedback with respect to the processor that I'm
using. Hopefully this is not considered spam.


~felix