* used for the value lookup, and the AtomicComparer used to compare values.
*/
public Object map(Item item, XPathContext context, Object info) throws XPathException {
HashSet lookup = (HashSet)((Object[])info)[0];
AtomicSortComparer comparer = (AtomicSortComparer)((Object[])info)[1];
AtomicSortComparer.ComparisonKey key = comparer.getComparisonKey((AtomicValue)item);
if (lookup.contains(key)) {
return null;
} else {
lookup.add(key);
return item;