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Date: Thu, 25 Mar 2021 09:28:27 +0000
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Subject: Re: [PHP-DEV] [RFC] Auto-capture multi-line closures and
 shortfunctions take 2
From: rowan.collins@gmail.com (Rowan Tommins)

On 25/03/2021 04:12, Mike Schinkel wrote:

> Actually, there is a way to declare a local variable.  Use the long function syntax instead as there is no proposal to deprecate it.

That's not quite what I meant. I meant that you can't say "capture by 
default, but this variable is definitely local".

I'm guessing maybe "$foo = null;" at the top of the function would stop 
it auto-capturing, but the semantics of what exactly gets captured 
aren't spelled out in the RFC. That really needs to be added IMO.


> Instead of using array_filter() with a side-effect free closure, I use a for loop because it is easier to reason about visually.


Is that a bad thing? In many cases it's probably more efficient, and 
easier to read.




> It is not clear to me from reading the PEP how a "with" statement obviates the benefit of variable auto-capture? Maybe because I don't "think" in Python, so from reading their examples I cannot see how this relates?


I didn't mean to say that the "with" statement would replace closures in 
general, but it would make them unnecessary *for some specific use 
cases*. You mentioned:

 > prime examples are database transactions and using throw-aware 
buffering handlers.

If your current code looks something like this:

wrap_in_buffer(function($transaction) use ($to, $library, $thread, 
$author, $title, $library_name, $top_post) {
     doSomething($to, $library, $thread);
     andThenSomethingElse($author, $title, $library_name, $top_post);
});

That's a perfect use case for a Context Manager:

with ( wrap_in_buffer() ) {
     doSomething($to, $library, $thread);
     andThenSomethingElse($author, $title, $library_name, $top_post);
}

There's no callback, so no need to capture anything, and the 
implementation of all the try-catch-finally logic would be baked into 
the language, so the implementation of wrap_in_buffer() would also be 
much simpler.


Regards,

-- 
Rowan Tommins
[IMSoP]