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Date: Mon, 20 Jan 2014 16:08:47 +0400
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Subject: Re: [PHP-DEV] Introducing "Array Of" RFC
From: inefedor@gmail.com ("Nikita Nefedov")

On Mon, 20 Jan 2014 11:31:17 +0400, Patrick Schaaf <bof@bof.de> wrote:

> Regarding the N*M checking complexity, couldn't a little bit of memory
> alleviate the problem?
>
> For each array, have a "member type" pointer, initially NULL.
>
> When the member type needs to be checked for the first time, and that
> "member type" pointer is not already set, do an O(N) scan of the arrray,
> testing compatibility of all members against the hinted type. Error on
> mismatch, but when all members match, remember the type behind the  
> "member
> type" pointer.
>
> When the member type needs to be checked and the "member type" pointer  
> _is_
> set, just compare it to the hinted type O(1).
>
> There must be some overhead when elements are added to an array. Either
> "when member type is set, forget it", or even "when member type is  
> already
> set, check compatiility of the newly added element with the member type,
> and then remove member type on mismatch or keep it on match".
>
> Finally when arrays are copied, and "member type" is already set, copy it
> along with the array, Optionally some of the array functions like
> array_merge might be made aware of the scheme, too.
>
> BTW, I'm undecided regarding the need for the overall feature, from my
> rather limited personal coding practise it seems to me that whenever I am
> interested in member type checking I'm already looping over the array and
> can easily add up-front instanceof checks to the loops with suitable
> explicit error-out. Which I generally prefer over automatic errors,
> especially fatal ones, because _I_ control the error case behaviour.
>
> But I think _if_ such a scheme were added, the implementation described
> above would solve the O(N*M) problem with acceptable overall cost.
>
> best regards
>   Patrick

Hi Patrick,

I had this cache-idea too, but it will fail to get you any speedup if you  
check for array of interfaces (if you want to store objects of different  
classes but all this classes implement one interface). And this is the  
same reason why this proposal is very different from having typed array  
structure (cause, as long as I know, type of the typed array is always the  
end-class, objects of which will be stored in this array). So if we are  
proposing to add some new Spl structure - keep that in mind.

And again, reference to an element in the array can be used to change  
element of the array without affecting (and thus calling any of the  
functions related to) HT.