return comparator.isLess(((Pair)left).first, ((Pair)right).second);
return comparator.isLess(((Pair)left).first, ((Pair)right).first);
        public boolean isLess(Object left, Object right)        {            ASSERT(left instanceof Pair);            ASSERT(right instanceof Pair);            return comparator.isLess(((Pair)left).first, ((Pair)right).second);        }