NodeSet set = ((ArraySet)contextSet).getChildren(doc, contextNode.getGID());
NodeSet set = ((ArraySet)contextSet).getSiblings(doc, contextNode.getGID());
    public Value eval(StaticContext context, DocumentSet docs, NodeSet contextSet,     	NodeProxy contextNode) {        DocumentImpl doc = contextNode.getDoc();        NodeSet set = ((ArraySet)contextSet).getChildren(doc, contextNode.getGID());        // determine position of current node in the set        NodeProxy p;        double count = 1.0;        for(Iterator i = set.iterator(); i.hasNext(); count++) {            p = (NodeProxy)i.next();            if(p.gid == contextNode.gid && contextNode.doc.getDocId() == contextNode.doc.getDocId())                return new ValueNumber(count);        }        return new ValueNumber(-1);    }