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Date: Sun, 17 Jun 2012 20:53:38 +0100
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To: "internals@lists.php.net" <internals@lists.php.net>, 
 Lars Strojny <lars@strojny.net>
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Subject: Re: [PHP-DEV] Support negative indexes for arrays and strings
From: marc@easen.co.uk (Marc Easen)

Hi Lars,

I don't think there needs to be a new operator, as it is possible to 
achieve this behaviour without adding a new language construct. The odd 
thing with PHP as I'm sure you are aware of is that arrays can be either 
a lists or a dictionary. This is where this becomes quite difficult to 
implement:

Numerical keyed array:

     $a = array('foo', 'bar', 'baz');
     $a[0] === 'foo'

I would expect:

     $a[-1] === 'baz';

An string keyed array:

     $b = array('foo' => 1, 'bar' => 2, 'baz' => 3);
     $b[0] === 1;

Would generate an E_NOTICE:   PHP Notice:  Undefined offset: 0 in php 
shell code on line 1.
An negative offset would also generate the same E_NOTICE.

So going back to your point, the change would only be to numeric based 
arrays (list) and strings. It could be possible to string keyed arrays 
to be accessed by the numeric counter parts, but I'm not familiar to 
comment on if this is even possible.


It seems this topic has generated a lot of interest, I feel the best way 
to proceed would be to write a RFC. I've never written one before so 
could someone give me access to create a page on the RFC site or create 
a RFC for me and give me permission to update it, my username is 'easen'.

Thanks,
Marc


On 17/06/12 15:14, Lars Strojny wrote:
> Hi Marc,
>
> Am 11.06.2012 um 23:01 schrieb Marc Easen:
>
> [...]
>>> I don't see much of complex logic here, but $a[2] = 'a' would create a
>>> new array element if it does not exist, while $a[-2] can't. Not a big
>>> issue, but somewhat inconsistent I guess.
>>>
>> Please note I'm not referring the negative indexes in arrays, just strings. As I see strings as being simpler to implement and produce a greater benefit compared to supporting negative indexes for arrays. As arrays are more complex structures and adding this behaviour would complicate things somewhat.
> I would propose not to try implementing a different behavior for strings than it is for arrays. I think we need a more convenient way to access parts of a string/parts of an array than substr() and array_slice() provide. But this will most likely be a new operator.
>
> cu,
> Lars