2 questions about types

Question

First question is how can I override the default constructor (or add an exception to it). I have an object like this
create or replace type date_object as object
     (quarter     number,
     year          number(4),
     member procedure set_date(d in date_object),
     member procedure set_date(d in date),
     member procedure set_date(v_qtr in number, v_year in number),
     constructor function date_object(d in date_object) return self as result,
     constructor function date_object(d in date) return self as result,
     --overriding constructor function date_object(v_qtr number, v_year number) return self as result,
     member function to_string return varchar2,
     member function get_quarter return number,
     member function get_year return number,
     member function get_quarter_as_string return varchar2);
/I want to replace date_object(v_qtr number, v_year number) with a new constructor that will call an exception if the quarter number is not 1,2,3,4. Oracle will not let me declare or overide function constructor function date_object(v_qtr number, v_year number) return self as result
Second question is, can I have an ADT as a primary key. This is what I am required to do, but it is not working for me:
create table financial_data
     (bank_code     number(7)     references banks(bank_code),
     qdate          date_object,
     total_assets     number,
     current_liabilities     number,
     long_term_liabilities     number,
     operating_income     number,
     investment_income     number,
     expenses     number);
     constraint     fd_pk          primary key (bank_code, qdate));

Answer 1

It would be much more simple having just a date (year and quarter can be easily extracted from)
Regards
Etbin