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Subject: Re: Fwd: [PHP-DEV] clarify the destructuring list() concept
From: rowan.collins@gmail.com (Rowan Tommins)

On 5 January 2024 23:16:58 GMT, "M=C3=B6n=C3=B4me Epson" <glash=2Egnome@gma=
il=2Ecom> wrote:

>I try to follow the procedure of: https://wiki=2Ephp=2Enet/rfc/howto

Then I suggest you take a moment to think about what you're proposing to c=
hange, and write it out clearly, as in "I propose to make this code =2E=2E=
=2E do this =2E=2E=2E instead of this =2E=2E=2E" At the moment, your messag=
es contain a lot of open-ended questions, and examples that you can easily =
look up the current behaviour of yourself=2E

Keep in mind that there are millions of existing PHP applications which mi=
ght be impacted by your change=2E In general, changing something which is c=
urrently an error is not a problem; but if the code currently succeeds, the=
re is a chance that somebody somewhere is using it=2E You need to think abo=
ut how the change will affect that existing code=2E



>It seems to me that list() is not clearly specified=2E

Do you mean that the documentation of the feature is not clear? Or, that t=
here are cases where it's behaviour is inconsistent in some way?


>list() supports destructuring assignment for arrays=2E Do you have an opi=
nion
>on object destructuring ?

It might be interesting to allow an object on the right-hand side, and som=
ehow specify properties to extract from it=2E I would be less interested in=
 having an object on the left-hand side, which would presumably create an i=
nstance of stdClass,  which I find pointless=2E Others might disagree=2E



>*Do you think seeing list() as the reciprocal of a function call is
>interesting ?*

As I said previously, I would now always spell both array creation and arr=
ay destructuring with [] not with array() and list()=2E Neither have ever b=
ehaved like function calls, and I don't think thinking of them that way is =
helpful=2E

Instead, think of it as a way of specifying the content of an array, just =
like "hello $name" specifies the content of a string=2E Then think of array=
 destructuring as the reverse of that construction:

$arr =3D [$a, $b];
[$a, $b] =3D $arr;

$arr =3D ['a' =3D> $a, 'b' =3D> $b];
['a' =3D> $a, 'b' =3D> $b] =3D $arr;

$arr =3D [1 =3D> $b, 0 =3D> $a];
[0 =3D> $a, 1 =3D> $b] =3D $arr;

$arr =3D [$a, $b]; // keys 0 and 1 assigned by default
[1 =3D> $b, 0 =3D> $a] =3D $arr;

$arr =3D [1 =3D> $b, 0 =3D> $a];
[$a, $b] =3D $arr; // keys 0 and 1 taken by default=20

$arr =3D ['a' =3D> 1, $dynamicKey =3D> 2];
[$dynamicKey =3D> $two, 'a' =3D> $one] =3D $arr;



>Otherwise, how to use a default value, type hinting, nullable/optional
>variable=2E=2E=2E It's not interesting ?

Some of those could be useful in both array creation and array destructuri=
ng, but it's not as simple as copying the syntax of a function signature=2E=
 Again, I suggest you write down a specific feature you are proposing to ad=
d, and think about how it would work=2E



>There are many things that could be done with but don't work=2E For examp=
le :
>
>$array =3D [1, 2, 3];
>[=2E=2E=2E$values] =3D [=2E=2E=2E$array];

I can see this would be useful as a "rest of the values" syntax, as in:

$arr =3D [1,2,3,4,5];
[$first, $second, =2E=2E=2E$rest] =3D $arr;

It couldn't work as the exact inverse of construction, though; this is all=
owed:

$arr1 =3D [1, 2, 3];
$arr2 =3D [=2E=2E=2E$arr1, =2E=2E=2E$arr1];=20

But this wouldn't make any sense:

$arr2 =3D [1, 2, 3, 1, 2, 3];
[=2E=2E=2E$arr1, =2E=2E=2E$arr1] =3D $arr2;

Once again, a proposal of exactly how it would work would be interesting=
=2E


Regards,

--=20
Rowan Tommins
[IMSoP]