public int hashCodeBase() {
   Tuple subThis = new Tuple(fields.subList(0, fields.size() - 1));
   return subThis.hashCode();
 }
 public int compareToBase(Tuple other) {
   Tuple subThis = new Tuple(fields.subList(0, fields.size() - 1));
   Tuple subThat = new Tuple(other.fields.subList(0, other.fields.size() - 1));
   return subThis.compareTo(subThat);
 }