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Date: Mon, 16 Nov 2015 09:40:08 +0000
Message-ID: <CABHuAWxPrqBZXQ5s1gFqEUcpF4ugqvkvpO=tVV6i4T01AO3=TA@mail.gmail.com>
To: Lorenzo Fontana <fontanalorenz@gmail.com>
Cc: Daniel Persson <mailto.woden@gmail.com>, PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Immutable modifier
From: t.carnage@gmail.com (Chris Riley)

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On 16 November 2015 at 09:33, Lorenzo Fontana <fontanalorenz@gmail.com>
wrote:

> I really like the concept of immutability, but I think that it should be
> applicable at  instance level rather than declaration.
>
> I would also prefer another keyword than immutable.
>
> Final does not make the properties immutable, it makes the class not
> extensible.
> On Nov 16, 2015 10:24, "Daniel Persson" <mailto.woden@gmail.com> wrote:
>
>> Any differance from the final keyword?
>>
>> http://php.net/manual/en/language.oop5.final.php
>>
>> On Mon, Nov 16, 2015 at 10:15 AM, Chris Riley <t.carnage@gmail.com>
>> wrote:
>>
>> > Hi,
>> >
>> > There has been a lot of interest recently (eg psr-7) in immutable data.
>> I'm
>> > considering putting an RFC together to add language support for
>> immutables:
>> >
>> > immutable class Foo {
>> > public $bar;
>> > public function __construct($bar) {
>> > $this->bar = $bar;
>> > }
>> > }
>> >
>> > Immutable on a class declaration makes all (maybe only public?)
>> properties
>> > of the class immutable after construct; assigning to a property would
>> > result in a Fatal error.
>> >
>> > class Foo {
>> > public $bar;
>> > immutable public $baz;
>> > }
>> >
>> > Immutable on a property makes the property immutable once it takes on a
>> > none null value. Attempts to modify the property after this results in a
>> > fatal error.
>> >
>> > Any thoughts?
>> > ~C
>> >
>>
>
What instance level syntax would you propose?

$foo = new immutable bar();  ?

or

immutable $foo = new bar();

Gives less flexibility imo and less guarantees of correctness.

Consider the current user land implementation of immutable classes:

class Foo {
private $bar;
public function __construct($bar) {
$this->bar = $bar;
}

public function getBar() {
return $this->bar;
}
}

Is already done at declaration declaration based immutability is probably
more desirable.

What keyword would you suggest other than immutable?

~C

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