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Date: Thu, 25 Mar 2021 14:12:53 +0100
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To: internals@lists.php.net
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Subject: Re: [PHP-DEV] [RFC] Auto-capture multi-line closures and
 shortfunctions take 2
From: olleharstedt@gmail.com (=?UTF-8?Q?Olle_H=C3=A4rstedt?=)

I feel like some of these examples would be better covered by command
object pattern and data-transaction objects, instead of FP idioms.
wrap_in_buffer pretty clearly so.

2021-03-25 10:28 GMT+01:00, Rowan Tommins <rowan.collins@gmail.com>:
> 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]
>
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