> ../s[matches(@c, '^[ab]$') and matches(., $re)]/position()
>
> obviously wrong since it will always return 1, given the above XML, e.g., I need the position() in ../s not the position() of the resulting nodeset from the match criteria.

It sounds like instead of

/position()

you want

/preceding-sibling::s

wrapped in a count(1 + .....)


-- 
Andrew Welch
http://andrewjwelch.com
Kernow: http://kernowforsaxon.sf.net/