CREATE OR REPLACE TYPE POINT AS OBJECT
( X INT
, Y INT
, label VARCHAR(1),
CONSTRUCTOR FUNCTION Point
( X INT
, Y INT
, label VARCHAR) RETURN SELF AS RESULT);
/

CREATE OR REPLACE TYPE BODY POINT AS
Constructor FUNCTION Point
(   X INT
 ,  Y INT
 ,  label VARCHAR
 ) RETURN SELF AS RESULT
IS
BEGIN
    IF X<0 THEN
        RAISE_APPLICATION_ERROR(-20001,'X value cannot be less than 0');
    ELSIF Y<0 THEN
        RAISE_APPLICATION_ERROR(-20002,'Y value cannot be less than 0');
    END IF;
    self.x := x;
    self.y := y;
    self.label := label;
    RETURN;
  END;
END;
/

CREATE TABLE POINTS OF POINT
(UNIQUE(X,Y),UNIQUE(label))

INSERT INTO points
VALUES(point(2,1,'b'))
/

INSERT INTO points
VALUES(point(1,1,'a'))
/

INSERT INTO points
VALUES(point(1,2,'e'))
/

--repeat and try to make not unique inserts

SELECT REF(p)
FROM points P

SELECT p.ep1.x,p.ep2.x,p.ep1.y,p.ep2.y
FROM lines p

CREATE OR REPLACE TYPE LINE AS Object
( EP1 REF POINT,
  EP2 REF POINT,
CONSTRUCTOR FUNCTION Line
(EP1 REF POINT,
 EP2 REF POINT) RETURN SELF AS RESULT);
/

CREATE OR REPLACE TYPE BODY LINE AS
Constructor FUNCTION LINE
( EP1 REF POINT,
  EP2 REF POINT
) RETURN SELF AS RESULT
IS
    x1 INTEGER;
    x2 INTEGER;
    y1 INTEGER;
    y2 INTEGER;
    valid BOOLEAN := FALSE;
BEGIN
RAISE_APPLICATION_ERROR(-20011,'congratulations, you''ve won, its'' running the constructor');
SELECT DEREF(ep1).x INTO x1 FROM dual;
SELECT DEREF(ep1).y INTO y1 FROM dual;
SELECT DEREF(ep2).x INTO x2 FROM dual;
SELECT DEREF(ep2).y INTO y2 FROM dual;
    IF x1 = x2 THEN
        valid := TRUE;
    END IF;
    IF y1 = y2 THEN
        valid := TRUE;
    END IF;
    IF valid THEN
        SELF.ep1    := ep1; --assigning the argument to the attribute
        SELF.ep2    := ep2;
        RETURN;
    ELSE
        RAISE_APPLICATION_ERROR(-20003,'X values are not equal, not making a stright line');
    END IF;
  END;
END;
/

CREATE TABLE Lines OF Line;

INSERT INTO Lines
VALUES(LINE(SELECT REF(p) FROM points p WHERE p.label='b')
,LINE(SELECT REF(p) FROM points p WHERE p.label='a'))