Sequence seq = getArgument(0).eval(docs, contextSequence, contextItem);
Sequence seq = getArgument(0).eval(contextSequence, contextItem);
	public Sequence eval(		DocumentSet docs,		Sequence contextSequence,		Item contextItem)		throws XPathException {		Sequence seq = getArgument(0).eval(docs, contextSequence, contextItem);		IntegerValue posArg = (IntegerValue)			getArgument(1).eval(docs, contextSequence, contextItem).convertTo(Type.INTEGER);		long pos = posArg.getValue();		if(pos < 1 || pos > seq.getLength())			throw new XPathException("Invalid position: " + pos);		return seq.itemAt((int)pos - 1).toSequence();	}