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To: Sara Golemon <pollita@php.net>
Cc: internals@lists.php.net
In-Reply-To: <2B.E1.14828.4130D834@pb1.pair.com>
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Organization: InterJinn
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Date: Tue, 29 Nov 2005 20:51:54 -0500
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Subject: Re: [PHP-DEV] Labeled Break (nothing at all whatsoever to do with
	GOTO)
From: robert@interjinn.com (Robert Cummings)

On Tue, 2005-11-29 at 20:40, Sara Golemon wrote:
> But first, this word from our sponsor:
> Group A wants anything resembling goto to burn in the fires of hell
> Group B wants full non-crippled goto or nothing at all
> Group C wants partial goto (non-backward jumping) or nothing at all
> Groups B and C both (generally) want it called either GOTO or JUMP, not
> BREAK
> 
> Since no group this size will ever come to an agreement on something this
> divisive, I'd like to turn the topic to a completely different language
> feature which (might) please enough people to get a rousing consensus.
> 
> Actual labeled breaks.  Not the break+jump that was proposed earlier in the
> guise of a break statement, but an actual straightforward, no funny-business
> labeled break which does no more and no less than the current break N;
> construct, but allows the use of identifier labels rather than numbers which
> may change as the result of the addition or removal of break containers.
> 
> http://libssh2.org/patches/true_labeled_break.diff
> 
> Usage:
> 
> while FOO ($condition) {
>     /* statements */
>     break FOO;
>     /* more statements */
> }
> 
> Or a stacked example:
> 
> for FOO(;;) {
>     while BAR (true) {
>         foreach BAZ ($arr as $val) {
>             switch Foof ($value) {
>                 default:
>                     do Plop {
>                         break FOO;
>                     } while (false);
>             }
>         }
>     }
> }
> 
> Notes on this implementation:
> 
> * Labels can't be repeated in an ancestral line.  For example, the parser
> will throw an ERROR on the following:
> while FOO(true) {
>     while FOO(true) {
>         break FOO;
>     }
> }
> 
> * Labels can be repeated by siblings.  I'm not married to this, and it
> certainly has WTF potential.  This behavior is easily modified to throw an
> error.  I left it permissable because there was no technical reason to
> disallow it.  For example, the following is okay:
> while FOO(true) {
>     break;
> }
> while FOO(true) {
>     break FOO;
> }
> 
> * Labeled breaks also apply to continue;  For example:
> foreach FOO($arr as $key => $val) {
>     if ($key % 2) continue FOO;
>     if (empty(%key)) break FOO;
> }

Hello, I represent group B (not in any way officially or anything else
that might give my words an iota of weight), but I (*cough cough*) WE
think that the above break system would make a terrible system for
finite state machines. 

Additionally at this time I'd like to make clear that we are in support
for full uncrippled break WITHIN scope. Group A can feel free to travel
to the burning fires of hell and have a barbecue, and group C should
join us so that at least they get what they want as a subset.

As an aside, from what I've read, the multitude were in favour of
unrestricted goto. Quite a few were in favour of none at all (but not as
many as in group B) and those in favour of none at all had a large
subset that were in favour of unrestricted goto in the event that group
B should get their way :)

Cheers,
Rob.
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