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To: Stanislav Malyshev <stas@zend.com>
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Date: Wed, 18 Jun 2008 12:32:38 -0400
References: <4856A547.3080801@gmx.net> <698DE66518E7CA45812BD18E807866CE01B11811@us-ex1.zend.net> <cd5680a20806172336y4127faf4t37d409396482da34@mail.gmail.com> <FB990539-B2F4-4C78-AD84-FB79651660C9@wanderingknights.org> <4859234C.5010003@zend.com>
Subject: Re: [PHP-DEV] [PATCH] [RFC] Closures and lambda functions in PHP
From: gwynne@wanderingknights.org (Gwynne Raskind)

On Jun 18, 2008, at 11:01 AM, Stanislav Malyshev wrote:
>> The Lua interpreter handles this by resolving variable references  
>> as they're made; "someVariable1" is looked up in the closure's  
>> scope and not found, so the interpreter steps out one scope and  
>> looks for it
> You may get into a problem here - creator's scope may not exist when  
> you execute the closure, and using caller's scope would be very  
> unexpected - usually closures are intended to capture part of  
> creating environment, not calling environment. It would also impose  
> serious penalty if you just use undefined variable - you'd have to  
> go through whole stack up to the top.

This lookup happens at the time the closure is first declared, and the  
value is stored for later use by the closure; the calling scope  
doesn't need to exist anymore. The problem with going to the top of  
the stack is an issue, though; the Lua interpreter's idea of "scope"  
is rather different from PHPs, and it's not nearly the same penalty  
there.
>


-- Gwynne, Daughter of the Code
"This whole world is an asylum for the incurable."