Doubt in Looping over a collection...?

Question

Hello,
As i was goin through some collections topics .. i have understood the basics, but i am NOT able to understand this line ... *" l_tab(l_tab.last) := i; "*
DECLARE
TYPE t_tab IS TABLE OF exception_test.id%TYPE;
l_tab t_tab := t_tab();
BEGIN
-- Fill the collection.
FOR i IN 1 .. 100 LOOP
l_tab.extend;
l_tab(l_tab.last) := i;
END LOOP;
End;
Why it is assigning like ' l_tab.LAST '.....?? y not from FIRST place....???
Thanks

Answer 1

Aijaz Mallick wrote:
Tht's Correct ... But why only LAST & why not FIRST....???Perhaps if you look at the contents while you do it, you'll get an idea...
SQL> ed
Wrote file afiedt.buf
  1  declare
  2    type t_coll is table of integer;
  3    v_coll t_coll := t_coll();
  4    --
  5    procedure show_coll is
  6      v_str varchar2(2000);
  7    begin
  8      for x in 1..v_coll.last
  9      loop
10        v_str := ltrim(v_str||','||v_coll(x),',');
11      end loop;
12      dbms_output.put_line('Array Size: '||to_char(v_coll.last,'99')||' : '||v_str);
13    end;
14    --
15  begin
16    for i in 1..10
17    loop
18      v_coll.extend;
19      v_coll(v_coll.last) := i;
20      show_coll;
21    end loop;
22* end;
SQL> /
Array Size:   1 : 1
Array Size:   2 : 1,2
Array Size:   3 : 1,2,3
Array Size:   4 : 1,2,3,4
Array Size:   5 : 1,2,3,4,5
Array Size:   6 : 1,2,3,4,5,6
Array Size:   7 : 1,2,3,4,5,6,7
Array Size:   8 : 1,2,3,4,5,6,7,8
Array Size:   9 : 1,2,3,4,5,6,7,8,9
Array Size:  10 : 1,2,3,4,5,6,7,8,9,10
PL/SQL procedure successfully completed.Whereas, if you where using FIRST instead of LAST, you'd get...
SQL> ed
Wrote file afiedt.buf
  1  declare
  2    type t_coll is table of integer;
  3    v_coll t_coll := t_coll();
  4    --
  5    procedure show_coll is
  6      v_str varchar2(2000);
  7    begin
  8      for x in 1..v_coll.last
  9      loop
10        v_str := ltrim(v_str||','||v_coll(x),',');
11      end loop;
12      dbms_output.put_line('Array Size: '||to_char(v_coll.last,'99')||' : '||v_str);
13    end;
14    --
15  begin
16    for i in 1..10
17    loop
18      v_coll.extend;
19      v_coll(v_coll.first) := i;
20      show_coll;
21    end loop;
22* end;
SQL> /
Array Size:   1 : 1
Array Size:   2 : 2,
Array Size:   3 : 3,,
Array Size:   4 : 4,,,
Array Size:   5 : 5,,,,
Array Size:   6 : 6,,,,,
Array Size:   7 : 7,,,,,,
Array Size:   8 : 8,,,,,,,
Array Size:   9 : 9,,,,,,,,
Array Size:  10 : 10,,,,,,,,,
PL/SQL procedure successfully completed.
SQL>