[xsl] Alternative to except operator that preserves order?

[TW <zupftom@xxxxxxxxxxxxxx>]

I'm processing a sorted sequence of elements, recursively eliminating
elements that have already been processed.  I'm using "except" for
this purpose, but except destroys the order and returns the remaining
elements in document order, so I have to re-sort them every time.  Not
so much of a problem because the sequences are not very large, but I
wondered, whether in general there is a better idiom for preserving
the pre-sorted order in situations like this.  The archive didn't make
me any wiser.

Thomas W.