I have noticed a change in behavior in "goto" statements recently. Whereas a statement like "goto PLACE;" would work fine no matter where "PLACE:" was in my code, I've noticed that scripts that used to work are now failing at the "goto" statement.
I can probably work out an example if needed, but the general question is: have any restrictions been put on "goto" recently? What are the real criteria needed to be satisfied for the destination to be successfully found?
Thanks,
Dave
Perl-Win32-Users mailing list
Perl-Win32-Users (AT) listserv (DOT) ActiveState.com
To unsubscribe:

Message
From: "Dave Ressler" <perl (AT) nettenna (DOT) com>
To: "Perl List" <perl-win32-users (AT) listserv (DOT) ActiveState.com>
Sent: Wednesday, July 13, 2005 11:06 AM
Subject: Change in "goto" behavior

I have noticed a change in behavior in "goto" statements recently. Whereas
a statement like "goto PLACE;" would work fine no matter where "PLACE:" was
in my code, I've noticed that scripts that used to work are now failing at
the "goto" statement.

I can probably work out an example if needed, but the general question is:
have any restrictions been put on "goto" recently? What are the real
criteria needed to be satisfied for the destination to be successfully
found?

Check 'perldoc -f goto'. If that doesn't answer the query, post a simple
example that demonstrates the problem.

The 'goto' documentation has changed a little from 5.6 to 5.8. I don't know
whether that represents a change in functionality, or just a re-wording.

Cheers,
Rob

Perl-Win32-Users mailing list
Perl-Win32-Users (AT) listserv (DOT) ActiveState.com
To unsubscribe:

Why on earth are you using a goto statement? They are pernicious.

HL

7/12/05, Dave Ressler <perl (AT) nettenna (DOT) comwrote:

I have noticed a change in behavior in "goto" statements recently. Whereas
a statement like "goto PLACE;" would work fine no matter where "PLACE:" was
in my code, I've noticed that scripts that used to work are now failing at
the "goto" statement.
I can probably work out an example if needed, but the general question
is: have any restrictions been put on "goto" recently? What are the real
criteria needed to be satisfied for the destination to be successfully
found?
Thanks,
Dave

Perl-Win32-Users mailing list
Perl-Win32-Users (AT) listserv (DOT) ActiveState.com
To unsubscribe:

Perl-Win32-Users mailing list
Perl-Win32-Users (AT) listserv (DOT) ActiveState.com
To unsubscribe:

At 08:30 AM 7/13/2005, Hugh Loebner wrote:
>Why on earth are you using a goto statement? They are pernicious.

We have a goto in our code. I hate it, but there just isn't a good "switch"
or "case" statement in Perl yet (I think I've heard that it's planned), and
the following just isn't efficient enough for us:

if ($op = 'thisop') {
}
elsif ($op = 'thatop') {
}

There are hundreds of possible values for $op. Anyway, I don't know how
many people are aware of it, but the destination of a "goto" can be a
variable, e.g.

goto $op;

thisop:
do_this();
thatop:
do_that();

course, you then have to prevent the fall through from the code for
thisop: to the code for thatop:, but that's another matter. (We initially
used a "goto FINISH", but I hated that, too. You can use a "break" if
you're in a loop.) We use a method that I really don't have time to
describe now, but doesn't use a "goto". I hate goto's, but for the example
above, it's efficient and much clearer than e.g. setting up a hash of op
names and code to handle each op.

7/12/05, Dave Ressler <<mailto:perl (AT) nettenna (DOT) com>perl (AT) nettenna (DOT) comwrote:
>I have noticed a change in behavior in "goto" statements recently. Whereas
>a statement like "goto PLACE;" would work fine no matter where "PLACE:"
>was in my code, I've noticed that scripts that used to work are now
>failing at the "goto" statement.
>
>I can probably work out an example if needed, but the general question is:
>have any restrictions been put on "goto" recently? What are the real
>criteria needed to be satisfied for the destination to be successfully found?
>
>Thanks,
>Dave
>
>
>Perl-Win32-Users mailing list
><mailto:Perl-Win32-Users (AT) listserv (DOT) ActiveState.com>Perl-Win32-Users (AT) listserv (DOT) ActiveState.com
>
>To unsubscribe:
><>
>
>
>
>
>
>Scanned for Spam and Viruses.
>Content-Type: text/plain; charset="us-ascii"
>MIME-Version: 1.0
>Content-Transfer-Encoding: 7bit
>Content-Disposition: inline
>X-NAIMIME-Disclaimer: 1
>X-NAIMIME-Modified: 1
>
>
>Perl-Win32-Users mailing list
>Perl-Win32-Users (AT) listserv (DOT) ActiveState.com
>To unsubscribe:
>
>
>Scanned for Spam and Viruses.

Perl-Win32-Users mailing list
Perl-Win32-Users (AT) listserv (DOT) ActiveState.com
To unsubscribe:

At 15:55 2005-07-13, John Deighan wrote:
>but that's another matter. (We initially used a "goto FINISH", but I hated
>that, too. You can use a "break" if you're in a loop.) We use a method
>that I really don't have time to describe now, but doesn't use a "goto". I
>hate goto's, but for the example above, it's efficient and much clearer
>than e.g. setting up a hash of op names and code to handle each op.

I think you just demonstrated why the dispatch table really is the way to
go :)

For instance, did you remember to wrap the goto in an eval to catch missing
labels?

It's not that goto is inherently bad, but it has a so very, very, very
specific niche in modern languages with other program flow constructs. The
only useful example I can think of is in C where you can use it to simplify
resource allocation/deallocation. But in Perl no.

Unless, of course, you're talking about goto LINE:
http://search.cpan.org/~

;)

/J

-- -- -- - - - - -
Johan L Sourcerer @ Boss Casinos johanl AT DarSerMan.com

Latest bookmark: "TCP Connection Passing"
http://tcpcp.sourceforge.net/
dmoz: / 12

Perl-Win32-Users mailing list
Perl-Win32-Users (AT) listserv (DOT) ActiveState.com
To unsubscribe:

Hugh Loebner wrote:
My previous message was attached to the wrong posting.

I doubt very much whether there is any occasion where gotos are "most
appropriate." Please provide an example.

Check ot "Go To Statement
Considered Harmful" by Edsger W. Dijkstra

of course, this has been discredited in the following discussion
, for languages that do not have the
equivalent of last/next type constructs for exiting loops in the middle
of the loop (like C). it's a bit harder to find a justification while
coding in perl. :)

Perl-Win32-Users mailing list
Perl-Win32-Users (AT) listserv (DOT) ActiveState.com
To unsubscribe:

At 09:55 AM 7/14/2005, Lloyd Sartor wrote:
>My opinion is that the goto statement can be useful in error handling
>situations, particularly when parsing data. This removes the
>rarely-executed error handling code from the expected, normal processing
>code. This makes the normal code more cohesive, understandable, and
>maintainable (IM) because it remains sequential, uncluttered by
>unnecessary indentation, braces, etc. course, Perl provides synonyms
>for 'goto' in these scenarios (last, continue).

If you try it, you'll find that using eval {} and die() is much
better for error handling. Especially since you can die() in
arbitrarily nested subroutines. Even C (at least C++) has a similar
behavior via the "try" construct.

I think that it's absurd to claim that work done by Edsger W.
Dijkstra, one of the most brilliant minds in Computer Science, has
been discredited by someone with lesser credentials. The only case
where I think that a 'goto' is justified is when no other alternative
is available in the language you're using (usually a failing of the
language) that is as computationally efficient, and computational
efficiency is a major issue (it usually isn't). I've used it, but
only in a very few cases.

Personally (and I hope I'm not starting a spam war here), I feel the
same way about last and continue, which usually indicate a
not-too-well thought out loop condition. We have 101,396 lines of
production code with 2 goto's, 0 continue's and 7 last's.

Perl-Win32-Users mailing list
Perl-Win32-Users (AT) listserv (DOT) ActiveState.com
To unsubscribe: