public Sequence eval(StaticContext context, DocumentSet docs, Sequence contextSequence, Item contextItem) throws XPathException {
public Sequence eval(DocumentSet docs, Sequence contextSequence, Item contextItem) throws XPathException {
	public Sequence eval(StaticContext context, DocumentSet docs, Sequence contextSequence, 		Item contextItem) throws XPathException {		if(getArgumentCount() < 2)			throw new XPathException ("concat requires at least two arguments");		if(contextItem != null)			contextSequence = contextItem.toSequence();		StringBuffer result = new StringBuffer();		for(int i = 0; i < getArgumentCount(); i++) {			result.append(getArgument(i).eval(context, docs, contextSequence).getStringValue());		}		return new StringValue(result.toString());	}