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Date: Sat, 18 Sep 2021 01:32:56 -0400
Cc: "internals@lists.php.net" <internals@lists.php.net>
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To: tyson andre <tysonandre775@hotmail.com>
Subject: Re: [PHP-DEV] RFC: Add `final class Vector` to PHP
From: mike@newclarity.net (Mike Schinkel)

> On Sep 16, 2021, at 10:09 PM, tyson andre <tysonandre775@hotmail.com> =
wrote:
>=20
> Hi internals,
>=20
> I've created a new RFC https://wiki.php.net/rfc/vector proposing to =
add `final class Vector` to PHP.
>=20
> PHP's native `array` type is rare among programming language in that =
it is 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 =
internal array HashTable API to the PHP's internals and PECLs, =
additional memory is needed to track keys =
(https://www.npopov.com/2014/12/22/PHPs-new-hashtable-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 =
least 8 elements to make the initial resizing more efficient, =
potentially wasting memory.
>=20
> It would be useful to have an efficient variable-length container in =
the standard library for the following reasons:=20
>=20
> 1. To save memory in applications or libraries that may need to store =
many lists of values and/or run as a CLI or embedded process for long =
periods of time=20
>   (in modules identified as using the most memory or potentially =
exceeding 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` for use cases=20
>   where objects are easier to use than arrays - e.g. variable sized =
collections (For lists of values) that can be passed by value to be read =
and modified.
> 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.
>=20
> Thoughts on Vector?

Given there seems to be a lot of concern about the approach the RFC =
proposes would it not address the concerns about memory usage and =
performance if several methods were added to SplFixedArray instead (as =
well as functions like indexOf(), contains(), map(), filter(), =
JSONSerialize(), etc., or similar):

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

setCapacity(int) =E2=80=94 Sets the Capacity, i.e. the maximum Size =
before resize
getCapacity():int =E2=80=94 Gets the current Capacity.

setGrowthFactor(float) =E2=80=94 Sets the Growth Factor for push(). =
Defaults to 2
getGrowthFactor():float =E2=80=94 Gets the current Growth Factor

pop([shrink]):mixed =E2=80=94 Returns [Size] then subtracts 1 from Size. =
If (bool)shrink passed then call shrink().
push(mixed) =E2=80=94 Sets [Size]=3Dmixed, then Size++, unless =
Size=3DCapacity then setSize(n) where n=3Dround(Size*GrowthFactor,0) =
before Size++.

grow([new_capacity]) =E2=80=94 Increases memory allocated. Sets Capacity =
to Size*GrowthFactor or new_capacity.
shrink([new_capacity]) =E2=80=94 Reduces memory allocated. Sets Capacity =
to current Size or new_capacity.

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

If you had these methods then I think you would get the memory and =
performance improvements you want, and if you really want a final Vector =
class for your own uses you could roll your own using inheritance or =
containment.

Would this not work?

-Mike

P.S. I also think asking for new methods on SplFixedArray has a much =
greater chance of successful than an RFC for Vector. #jmtcw