Eddie Awad’s Blog - Latest Comments in What’s in a Label

Re: What’s in a Label

Duke Ganote — Mon, 11 Aug 2008 08:33:41 -0000

Wow. I'm moving pl/sql IF statements into the trash bin along side GOTOs, now that I see I can use labeled CASE instead. (Nested IFs are such a pain to visually decipher.)

Re: What’s in a Label

Eddie Awad — Fri, 17 Feb 2006 15:32:42 -0000

APC: I was merely pointing out that raising an exception is a special case of GOTO.

Ah! I see. when you raise an exception, you basically "go to" the corresponding exception block.

APC: Before I started in Oracle I worked on a particular flavour of COBOL that didn't support conditional ERFORMs. GOTOs were a way of life.

I started my programming career with COBOL, that was in 1992. COBOL and GOTO were best buddies.

In PL/SQL, I just cannot see a real need to use labels and GOTO's. Labels can be easily replaced with comments. GOTO's can be easily replaced with many other programming controls that provide a much better clarity to the program logic.

Re: What’s in a Label

FranÃ§ois Degrelle — Fri, 17 Feb 2006 08:14:55 -0000

Label could be an elegant solution to exit 2 nested loop

SQL> Declare
  2    LN$I pls_integer := 0 ;
  3    LN$J pls_integer := 0 ;
  4  Begin
  5    <<boucle1>>
  6    Loop
  7      LN$I := LN$I + 1 ;
  8      Loop
  9         LN$J := LN$J + 1 ;
 10         dbms_output.put_line( to_char( LN$I ) || ',' || to_char( LN$J ) ) ;
 11         EXIT boucle1 WHEN LN$J > 3 ;
 12      End loop ;
 13    End loop ;
 14  End ;
 15  /
1,1
1,2
1,3
1,4

ProcÃ©dure PL/SQL terminÃ©e avec succÃ¨s.

Re: What’s in a Label

Krishna — Fri, 17 Feb 2006 07:33:14 -0000

[OT] I don't think Dijkstra has revoked his fatwa.

I don't think he will ever be able to revoke it given that he passed away few years back :(

Re: What’s in a Label

APC — Fri, 17 Feb 2006 04:45:47 -0000

And what's wrong with GOTOs anyway? haven't they been officially considered not harmful for sometime now?

They have? Nobody tells me anything.

Actually I was thinking about the NTK newsletter and not some computer science pronouncement. I don't think Dijkstra has revoked his fatwa. Still, if you've ever had to follow the possible paths through a function that has over a dozen RETURN statements you might find yourself pining for a nice GOTO exit_point.

GOTOs are like triggers: there's nothing inherently wrong with the construct, it's simply the potential for abuse that renders their use suspect. Simply avoiding the use of GOTO statement does not make our code well-structured.

Re: What’s in a Label

APC — Fri, 17 Feb 2006 04:33:40 -0000

I take it you use GOTO to raise exceptions

Of course not. I was merely pointing out that raising an exception is a special case of GOTO. Particularly given a case like this:

    ....
    do_something_a;
    do_something_b;
EXCEPTION
   WHEN others THEN blah;

If do_something_a raises an exception to be handle by the calling program then essentially there is an invisible GOTO that bypasses do_something_b.

Before I started in Oracle I worked on a particular flavour of COBOL that didn't support conditional ERFORMs. GOTOs were a way of life. So I know bad use of GOTO create spaghetti code. I also know that well structured GOTOs have their place.

Of course, Oracle PL/SQL has a panoply of control structures and I have never had to use a GOTO since I stopped COBOLing. Indeed the other day I found myself with a LOOP that had more than one EXIT statement and felt unclean.

Re: What’s in a Label

Tom_Fox — Thu, 16 Feb 2006 15:50:10 -0000

I'm not a developer, but the term GOTO reminds me of writing BASIC on my Commodore 64. I can't believe it still exists, besides in Windows batch files.

Re: What’s in a Label

Eddie Awad — Thu, 16 Feb 2006 14:19:42 -0000

I take it you never raise exceptions either

I take it you use GOTO to raise exceptions ;)

Re: What’s in a Label

William Robertson — Thu, 16 Feb 2006 12:42:07 -0000

> And what's wrong with GOTOs anyway? haven't they been officially considered not harmful for sometime now?

They have? Nobody tells me anything.

Re: What’s in a Label

Tim Hall — Thu, 16 Feb 2006 11:23:50 -0000

I don't use GOTOs, but I do use labels for loops sometimes. It's really a clarity thing. If I have nested loops, the labels are handy to see which loop has ended, although a comment would do the same. I also use labels if I'm planning to exit a loop prematurely.

Cheers

Tim...

Re: What’s in a Label

Peter Lorenzen — Thu, 16 Feb 2006 11:17:34 -0000

I use labels in 3 situations: Loops, case statement and begin end block inside a procedure/function. I like that you can end the case or the begin with a label like this:

<<myBlock>>
begin
  x := y + 1;
end myBlock;

<<myCase>>
case xx
  when ..
end case myCase;

Re: What’s in a Label

yas — Thu, 16 Feb 2006 10:21:45 -0000

Unfortunately there are lots of developers insisting to use goto's. It is a tradition some people cannot give up.
It was imposible to get a degree for students using goto's in their assignments in my college years.

Re: What’s in a Label

APC — Thu, 16 Feb 2006 08:30:11 -0000

You missed what I think is a genuine use for labels: identifying nested loops.

<<dept>>
FOR d_rec IN ( SELECT deptno FROM scott.dept ) LOOP
   do_whatever;
   <<emp>>
   FOR e_rec IN (SELECT empno FROM scott.emp
                          WHERE deptno = d_rec.deptno ) LOOP
       blah(e-rec.empno);
   END LOOP emp;
   clean_up;
END LOOP dept;

And what's wrong with GOTOs anyway? haven't they been officially considered not harmful for sometime now? I take it you never raise exceptions either.

Cheers, APC