*/
public Item evaluateItem(XPathContext c) throws XPathException {
AtomicValue gp0 = (AtomicValue)argument[0].evaluateItem(c);
NumericValue gp = (NumericValue)gp0.getPrimitiveValue();
RegexIterator iter = c.getCurrentRegexIterator();
if (iter == null) return null;
String s = iter.getRegexGroup((int)gp.longValue());
if (s == null) return null;
return new StringValue(s);
}