Re: [PATCH] [RFC] Closures and lambda functions in PHP

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."