Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:98965
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: softfail (pb1.pair.com: domain golemon.com does not designate 74.125.82.53 as permitted sender)
MIME-Version: 1.0
Sender: php@golemon.com
In-Reply-To: <CAF1yvARPJnxBecX5e-dd4Bb5qQ4MqMxYg0Rv7cNf94Rs+i8m2Q@mail.gmail.com>
References: <CAF1yvARPJnxBecX5e-dd4Bb5qQ4MqMxYg0Rv7cNf94Rs+i8m2Q@mail.gmail.com>
Date: Thu, 4 May 2017 10:52:11 -0500
Message-ID: <CAESVnVps7TMViBz6besqAzHcuHHuUy-4DD7vOGf1MCi+qEG=og@mail.gmail.com>
To: Jesse Schalken <me@jesseschalken.com>
Cc: PHP internals <internals@lists.php.net>
Content-Type: text/plain; charset=UTF-8
Subject: Re: [PHP-DEV] Add is_vectorlike($array) function
From: pollita@php.net (Sara Golemon)

On Tue, May 2, 2017 at 4:13 AM, Jesse Schalken <me@jesseschalken.com> wrote:
> The problem is that this function is O(n), but in PHP7 an array that is
> vector-like is likely to be packed and without holes (HT_IS_PACKED(x) &&
> HT_IS_WITHOUT_HOLES(x)), in which case it is known to be vector-like
> without needing to iterate over it,
>
Just want to underline the "is likely to be" part of this sentence.
The implementation can't assume an array is not vector-like just
because those checks fail.  It's possible to manipulate an array into
being vector-like, but not packed, or having holes.

Not really commenting on the proposal yet, which I'm a big
shoulder-shruggy about.  Just highlighting the caveat for any eventual
implementation.  We can short-circuit the O(n) loop if it *is*
packed/no-holes, but if not then we need to walk it to be certain.
This is probably fine since this check is likely used in places where
the array is expected to be vector like and non-vector should be a
slow path anyway.

-Sara