Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:93942
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain gmx.de designates 212.227.17.20 as permitted sender)
To: Levi Morrison <levim@php.net>, Christoph Becker <cmbecker69@gmx.de>
References: <8284FE1F-70EE-4DB6-A945-0C57A4C99DCC@trowski.com>
 <16ef864f-8378-1af3-ddfb-21dc583a4b4a@gmx.de>
 <CAFMT4NrTDLhU912CQH55Y8z+M0s_qyP_FOxLKALwUcV0xB52Fw@mail.gmail.com>
Cc: Aaron Piotrowski <aaron@trowski.com>,
 PHP internals <internals@lists.php.net>
Message-ID: <db9a6db5-16c0-cb1d-5a1d-a99472ecb73b@gmx.de>
Date: Mon, 13 Jun 2016 18:52:33 +0200
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101
 Thunderbird/45.1.1
MIME-Version: 1.0
In-Reply-To: <CAFMT4NrTDLhU912CQH55Y8z+M0s_qyP_FOxLKALwUcV0xB52Fw@mail.gmail.com>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit
Subject: Re: [PHP-DEV] Re: [RFC] Iterable
From: cmbecker69@gmx.de (Christoph Becker)

On 13.06.2016 at 17:59, Levi Morrison wrote:

> On Mon, Jun 13, 2016 at 5:42 AM, Christoph Becker <cmbecker69@gmx.de> wrote:
>> On 11.06.2016 at 01:37, Aaron Piotrowski wrote:
>>> I would like to propose a new iterable pseudo-type that accepts both arrays and objects implementing Traversable. Values accepted by iterable can then be used with foreach and yield from, or help to reduce type-checking logic in general.
>>>
>>> Please review the RFC here: https://wiki.php.net/rfc/iterable <https://wiki.php.net/rfc/iterable>
>>
>> Thanks, Aaron!  I definitely like this idea (I'm not sure about the
>> details yet – would have to thoroughly investigate), as it is apparently
>> solving a long-standing issue, and is in my opinion a cleaner solution
>> than (explicitly) having to resort to a union type.
> 
> My opinion is contrary: the union type is the cleaner solution as it
> does not require special casing machinery in the engine.

I agree that union types are the cleaner solution with regard to the (C)
implementation.  I don't think, though, that they are the cleaner
solution with regard to PHP code; a developer has to think twice which
guarantees a union types gives regarding the allowed operations.  For
instance, what would Foo|Bar guarantee?  I would have to look up both
respective definitions and find the intersection – and that still leaves
room for errors, as operations with the same name do not guarantee
equivalent behavior.  The special case of reading and understanding
`Traversable|array` might quickly get second nature for developers, but
it's still ugly to write and read, in my opinion.

-- 
Christoph M. Becker