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Date: 29 Jul 2004 10:40:20 -0400
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Subject: Re: [PHP-DEV] GOTO operator
From: robert@interjinn.com (Robert Cummings)

On Thu, 2004-07-29 at 10:17, Leonardo Pedretti wrote:
> Goto is somewhat equivalent to 'case' combined with using 'continue' in loops. 
> More precisely, this 2 language constructions are the 'goto' implementation 
> with a different name so that Dijkstra does not get back from the grave to 
> punish us =D
> It is true that goto is a little 'off-paradigm' in OOP and truly structured 
> languages, however, the point is this: sometimes continue and case produce 
> code that is not so clear and small at the same time as a little well used 
> goto. BUT goto allows non experienced or not well educated programmers to 
> begin writing horrible and totally unstructured code, and go further 
> developing bad programming habits... IMHO, would php be a more restrictive 
> language (strongly typed, or something alike) I would be totally and 
> unconditionally on for a goto addon. However, i see the bad habits and bad 
> code promotion as something that should be very carefully noted before 
> deciding whether to apply it or not.
> I hope i have added some good points to help make the consideration deeper and 
> better =)

While it is true you can approximate the functionality of goto using
switch, or if/elseif/else constructs, these are inferior in efficiency.
Evaluation via switch or if/elseif/else system is O(n) just to get to
the desired block of code. Using goto, getting to the chosen code block
is O(1) (see note below). This is probably the most important reason why
many parsing implementations use goto.

Note
----
Goto jumping is O(1) if getting to the jump destination doesn't require
a hash lookup due to "wuring" of the destination at compile time. If a
hash lookup is required then it is probably something like O(lg n) which
is still superior in efficiency to O(n). Additionally, while it is true
that an O(lg n) lookup might be necessary at compile time to find the
pointer to the labeled code block, this is a one time event and has
little bearing on the efficiency overall when during runtime the goto
might be hit thousands or millions of times.

Cheers,
Rob.
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