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Date: Sun, 13 May 2012 19:10:45 +0200
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Subject: Re: [PHP-DEV] Array decomposition, more than list()
From: ivan.enderlin@hoa-project.net ("Ivan Enderlin @ Hoa")

Hi Clint,

On 13/05/12 18:41, Clint Priest wrote:
> I've been using array decomposition in other languages such as Javascript recently and find it very useful.  I did not find any conversation about it in the archives, has this topic been discussed/vetted/shot down already?
>
> Example use case: Indexed database results being iterated:
>
> Input:
> $tValues[$dbRow['ID1']][$dbRow['ID2']][$dbRow['ID3']] = $dbRow['Value'];
>
> Output:
> foreach($tValues as $ID1 => $tSubValues1) {
>      foreach($tSubValues1 as $ID2 => $tSubValues2) {
>          foreach($tSubValues2 as $ID3 => $Value) {
>              /* Do something, such as build an SQL insert */
>          }
>      }
> }
>
> The above is a semi-common piece of code in our production application, I could see list decomposition as a very convenient alternative.
>
> New functionality would support:
>
> foreach($tValues as $ID1 => [$ID2 => [$ID3 => $Value] ]) {
>      /* Do something */
> }
>
> The above also would indicate that associative array key decomposition would also be allowed.  I don't believe anything like the above is possible, even outside of a foreach loop, but perhaps I am wrong there.
The semantics of list() and foreach are different. A list() extracts 
data in variables, whereas a foreach is a loop that iterates over a 
structured data. Of course, I assume you know that. But what is the 
semantics you give to foreach($array as $key1 => [$key2 => [$key3 => 
$value]])? Are you interating on $key1, then $key2, then $key3, or just 
unfolding/extracting these variables? In other terms, what happened when 
$key1 has more than 1 value? Do we iterate or extract? It is not clear here.
Could you point out some references (e.g. from Javascript)?

Best regards.

-- 
Ivan Enderlin
Developer of Hoa
http://hoa.42/ or http://hoa-project.net/

PhD. student at DISC/Femto-ST (Vesontio) and INRIA (Cassis)
http://disc.univ-fcomte.fr/ and http://www.inria.fr/

Member of HTML and WebApps Working Group of W3C
http://w3.org/