Implementing First In First Out Behaviour Using PL/SQL object types

Question

Hi Friends,
I have a Integer Array of type Varray, I want to implement first in first out behaviour using Pl/SQL object type.Please provide me some idea that i can proceed. If you can provide me any sample code or any documentation,i will be very much thankful to you.Eagerly waiting for your reply.
Thanks

Answer 1

basically i have to implement a queue using pl/sql object types to traverse a tree as we can implement stack (LIFO).
I can give an example of Stack implementation...
CREATE or replace TYPE IntArray AS VARRAY(50) OF INTEGER;
CREATE or replace TYPE IntStack_O AS OBJECT (
maximalSize INTEGER
,top INTEGER
,position IntArray
,MEMBER PROCEDURE initialize
,MEMBER FUNCTION full RETURN BOOLEAN
,MEMBER FUNCTION empty RETURN BOOLEAN
,MEMBER FUNCTION getAnzahl RETURN INTEGER
,MEMBER PROCEDURE push (n IN INTEGER)
,MEMBER PROCEDURE pop (n OUT INTEGER)
CREATE or replace TYPE body IntStack_O AS
MEMBER PROCEDURE initialize IS
BEGIN
top := 0;
-- Call Constructor und set element 1 to NULL
position := IntArray(NULL);
maximalSize := position.LIMIT; -- Get Varray Size
position.EXTEND(maximalSize -1, 1); -- copy elements 1 in 2..50
END initialize;
MEMBER FUNCTION full RETURN BOOLEAN IS
BEGIN
RETURN (top = maximalSize); — Return TRUE when Stack is full
END full;
MEMBER FUNCTION empty RETURN BOOLEAN IS
BEGIN
RETURN (top = 0); — Return TRUE when Stack is empty
END empty;
MEMBER FUNCTION getAnzahl RETURN integer IS
BEGIN
RETURN top;
END;
MEMBER PROCEDURE push (n IN INTEGER) IS
BEGIN
IF NOT full
THEN
top := top + 1; — Push Integer onto the stack
position(top) := n;
ELSE
–Stack ist voll!
RAISE_APPLICATION_ERROR(-20101, ‘Error! Stack overflow. ‘
||’limit for stacksize reached.’);
END IF;
END push;
MEMBER PROCEDURE pop (n OUT INTEGER) IS
BEGIN
IF NOT empty
THEN
n := position(top);
top := top -1; — take top element from stack
ELSE
–Stack ist leer!
RAISE_APPLICATION_ERROR(-20102, ‘Error! Stack underflow. ‘
||’stack is empty.’);
END IF;
END pop;
END;
Now if i run this..i will be getting the following output...
DECLARE
stack intstack_o := intstack_o(NULL,NULL,NULL);
a INTEGER;
BEGIN
stack.initialize;
dbms_output.put_line('Anzahl: ' || stack.getAnzahl);
stack.push(1111);
dbms_output.put_line('Anzahl: ' || stack.getAnzahl);
stack.push(1112);
dbms_output.put_line('Anzahl: ' || stack.getAnzahl);
stack.push(1113);
dbms_output.put_line('Anzahl: ' || stack.getAnzahl);
stack.pop(a);
dbms_output.put_line('Anzahl: ' || stack.getAnzahl);
dbms_output.put_line(a);
stack.pop(a);
dbms_output.put_line('Anzahl: ' || stack.getAnzahl);
dbms_output.put_line(a);
stack.pop(a);
dbms_output.put_line('Anzahl: ' || stack.getAnzahl);
dbms_output.put_line(a);
stack.pop(a);
dbms_output.put_line('Anzahl: ' || stack.getAnzahl);
dbms_output.put_line(a);
END;
Output...
Anzahl: 0
Anzahl: 1
Anzahl: 2
Anzahl: 3
Anzahl: 2
1113
Anzahl: 1
1112
Anzahl: 0
1111
Above is the Stack (Last In First Out) Implementations of integer array.Now my Requirement is Queue(First In First Out) Implementation of Integer array.