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Reply-To: Levi Morrison <levi.morrison@datadoghq.com>
Date: Thu, 16 Sep 2021 20:50:09 -0600
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To: tyson andre <tysonandre775@hotmail.com>
Cc: "internals@lists.php.net" <internals@lists.php.net>
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Subject: Re: [PHP-DEV] RFC: Add `final class Vector` to PHP
From: internals@lists.php.net ("Levi Morrison via internals")

On Thu, Sep 16, 2021 at 8:10 PM tyson andre <tysonandre775@hotmail.com> wro=
te:
>
> Hi internals,
>
> I've created a new RFC https://wiki.php.net/rfc/vector proposing to add `=
final class Vector` to PHP.
>
> PHP's native `array` type is rare among programming language in that it i=
s used as an associative map of values, but also needs to support lists of =
values.
> In order to support both use cases while also providing a consistent inte=
rnal array HashTable API to the PHP's internals and PECLs, additional memor=
y is needed to track keys (https://www.npopov.com/2014/12/22/PHPs-new-hasht=
able-implementation.html - around twice as much as is needed to just store =
the values due to needing space both for the string pointer and int key in =
a Bucket, for non-reference counted values)).
> Additionally, creating non-constant arrays will allocate space for at lea=
st 8 elements to make the initial resizing more efficient, potentially wast=
ing memory.
>
> It would be useful to have an efficient variable-length container in the =
standard library for the following reasons:
>
> 1. To save memory in applications or libraries that may need to store man=
y lists of values and/or run as a CLI or embedded process for long periods =
of time
>    (in modules identified as using the most memory or potentially exceedi=
ng memory limits in the worst case)
>    (both in userland and in native code written in php-src/PECLs)
> 2. To provide a better alternative to `ArrayObject` and `SplFixedArray` f=
or use cases
>    where objects are easier to use than arrays - e.g. variable sized coll=
ections (For lists of values) that can be passed by value to be read and mo=
dified.
> 3. To give users the option of stronger runtime guarantees that property,=
 parameter, or return values really contain a list of values without gaps, =
that array modifications don't introduce gaps or unexpected indexes, etc.
>
> Thoughts on Vector?
>
> P.S. The functionality in this proposal can be tested/tried out at https:=
//pecl.php.net/teds (under the class name `\Teds\Vector` instead of `\Vecto=
r`).
> (That is a PECL I created earlier this year for future versions of iterab=
le proposals, common data structures such as Vector/Deque, and less commonl=
y used data structures that may be of use in future work on implementing ot=
her data structures)
>
> Thanks,
> Tyson
> --
> PHP Internals - PHP Runtime Development Mailing List
> To unsubscribe, visit: https://www.php.net/unsub.php
>

I'm okay with a final Vector class in general. I don't love the
proposed API but don't hate it either. Feedback on that at the end.

What I would _love_ is a `vec` type from hacklang, which is similar to
this but pass-by-value, copy-on-write like an array. Of course, this
would require engine work and I understand it isn't as simple to add.

Feedback on API:

-  `indexOf` returning `false` instead of `null` when it cannot be
found. If we are keeping this method (which I don't like, because
there's no comparator), please return `null` instead of false. The
language has facilities for working with null like `??`, so please
prefer that when it isn't needed for BC (like this, this is a new
API).
- `contains` also doesn't have a comparator.
-  Similarly but less strongly, I don't like the filter callable
returning `mixed` -- please just make it `bool`.
- I don't know what `setSize(int $size)` does. What does it do if the
current size is less than `$size`? What about if its current size is
greater? I suspect this is about capacity, not size, but without docs
I am just guessing.