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Date: Wed, 18 Dec 2013 20:32:14 +0000
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To: Andrea Faulds <ajf@ajf.me>
Cc: PHP internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=089e0160caaebf418b04edd4f000
Subject: Re: [PHP-DEV] Re: RFC Proposal: New assign value operator
From: tom@scl.co.uk (Tom Oram)

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Sorry for the delay, I've been very busy. Before I let this go completely I
just want to give a couple of examples. I get the feeling I'm not going to
get anywhere with this but let me quickly just show a few things where I
think this would make life easier:

POINT 1 (mixing types including scalars):
-------------
Consider:

$emails = array(
    'someone@hotmail.com',
    new Email('bob@aol.com'),
    new AdvancedEmail('alice@yahoo.com'),
);

Now which of these is a nicer way to clear all the addresses?

foreach ($emails as &$email) {
    if ($email instanceof Email) {
        $email->setValue('');
    } elseif ($email instanceof AdvancedEmail) {
        $email->setAddress('');
    } else {
        $email = '';
    }
}

OR

foreach ($emails as &$emal) {
    $email := '';
}


POINT 2 (protecting against changing types):
-------------
Consider a library provides a base class called Product like so

class Product
{
    protected $price = 0.0;
 }

Next up someone extends this class in their application

class SpecialProduct
{
    /** @var float $price */
    public function specialSetPrice($price)
    {
        $this->doSomethingSpecial();

        $this->price = $price;
    }
}

Now the original library maintainers decide to use a value object for the
price changing Product to the following

class Product
{
    protected $price;

    public function __construct()
    {
        $this->price = new MoneyValue(0.0);
    }
}

At this point the original app developpers would have to update their
SpecialProduct so that

$this->price = $price;

becomes

$this->price = new MoneyValue($price);

HOWEVER if specialSetPrice had used

$this->price := $price;

from the start it would have adapted to any changes in type automatically
and therefore no modification would have had to be made. In fact the child
class didn't require any knowledge of the type defined in the parent. The
type is set once then used with not requirement to maintain consistency.


POINT 3 (it's nicer to use):
-------------
I'm sorry but if you have a String class which you're using all over the
place

$var := 'new value';

is so much more readable (to me at least) than

$var->setValue('new value');

To those that argue it's confusing with =, it's not, it's a different
operator it's :=, just like +=, if you come across a new operator in the
code which you havent seen before you got and look it up and find out what
it does, just like if you see ** for the first time if the pow() RFC goes
through.

And again if the designers decide to stop using a scalar and use an object
instead at some point all the assignments in the code won't have to be
fixed!


POINT 4 (argument against it can be done it other existing ways)
-------------
Before foreach came along we used

reset($array);
while (list($key, $value) = current($array)) {
    next($array);
}

So why did we need foreach?

This RFC
https://wiki.php.net/rfc/pow-operator?utm_content=buffer1f703&utm_source=buffer&utm_medium=twitter&utm_campaign=Buffer
suggests
a new ** operator which can be used instead of pow()

Why do we need that? pow() works just fine!

There are many many similar things in PHP's history and will be many more
i'm sure. Why did any of them get added? Because they make the code simpler
and easier to understand. I agree there's shouldn't be several ways to do
everything as it can lead to confusion and clutter but to say something is
no good because you can do it in another, more long winded way, I think is
a bit ridiculous.


Anyway, that's the last I'll say on it unless others show some interest.
But either way I'm interested to see what responses come back from this.

Everyday I am coding I come across at least 2 or 3 instances where I want
to use something like this.

Best regards to all,
Tom

On 27 November 2013 19:07, Andrea Faulds <ajf@ajf.me> wrote:

> On 27/11/13 09:36, Tom Oram wrote:
>
>>
>> Since writing the original message I've been looking at golang and found
>> that they have a := operation to infer type which is very similar to what
>> I
>> proposed.
>>
>> I'd like to try and start some discussion about this again as I think it
>> would be very useful and really open up the possibility of having objects
>> for primitive types.
>>
>>
> I'm not sure I understand the utility here. PHP has a dynamic typing
> system. The utility of := in languages like Go is that it allows you to
> avoid making a type declaration. But PHP does not have them anyway, so
> there it isn't useful in that case.
>
> --
> Andrea Faulds
> http://ajf.me/
>
>
> --
> PHP Internals - PHP Runtime Development Mailing List
> To unsubscribe, visit: http://www.php.net/unsub.php
>
>


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