SPUG: Loop styles: goto vs. redo

[Richard Anderson]

I'd have to concur with David's point that "the change of flow is much more
limited with redo than with goto" and his suggestion to use redo with a
label for extra clarity:

START_TESTS: {
    my $done = 1;
    for  (....) {
        unless(...) {
            ...
            $done = 0;
        }
    }
    redo START_TESTS unless $done;
}

Cheers,
Richard
richard at richard-anderson.org
www.richard-anderson.org
www.raycosoft.com
----- Original Message -----
From: "David Dyck" <dcd at tc.fluke.com>
To: "Richard Anderson" <richard at richard-anderson.org>
Cc: <spug-list at pm.org>
Sent: Tuesday, July 02, 2002 10:45 AM
Subject: Re: SPUG: Loop styles: goto vs. redo


> On Mon, 1 Jul 2002 at 21:10 -0700, Richard Anderson
<richard at richard-anders...:
>
> > For production code, which is better...
> >
>
> LINE:
> > {
> >     my $done = 1;
> >     for  (....) {
> >         unless(...) {
> >             ...
> >             $done = 0;
> >         }
> >     }
>       redo LINE unless $done;
> > }
>
>
> I'd suggest adding a label on your loop.
>
> from perldoc -f goto I'll quote
>     "The author of Perl has never felt the need to use this form of "goto"
>     (in Perl, that is--C is another matter).  (The difference being that
>     C does not offer named loops combined with loop control.  Perl does,
>     and this replaces most structured uses of "goto" in other languages.)"
>
> The label on the loop is a good clue that something is
> going on, and the change of flow is much more limited
> with redo than with goto, so I'd suggest using redo.
> If you are going to redo back more that a couple of lines
> I would strongly suggest using the label on the loop.
>
> Judging from your omited code "....", you could eliminate
> the $done variable, and have the redo action happen
> closer to the condition that set $done to 0, (undone)
> if you rewrite as:
>
> LINE:
> {
>     for  (....) {
>         unless(...) {
>             ...
>             redo LINE;
>         }
>     }
> }
>
>




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