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To: Patrick Schaaf <bof@bof.de>, Larry Garfield <larry@garfieldtech.com>
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Subject: Re: [PHP-DEV] Introducing "Array Of" RFC
From: rasmus@lerdorf.com (Rasmus Lerdorf)

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On 1/19/14, 11:31 PM, Patrick Schaaf wrote:
> Regarding the N*M checking complexity, couldn't a little bit of memory
> alleviate the problem?
>=20
> For each array, have a "member type" pointer, initially NULL.
>=20
> 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 "mem=
ber
> type" pointer.
>=20
> When the member type needs to be checked and the "member type" pointer =
_is_
> set, just compare it to the hinted type O(1).
>=20
> 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 alre=
ady
> set, check compatiility of the newly added element with the member type=
,
> and then remove member type on mismatch or keep it on match".

This means every HT becomes larger now and every time you write to a HT
you at the very least need to do one extra comparison. We use HTs
everywhere, so this would have a performance impact on every script even
if you have absolutely no intention of ever using this feature.

-Rasmus


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