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Date: Tue, 17 Jul 2018 09:24:24 -0300
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To: Levi Morrison <levim@php.net>
Cc: internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Replacing array_slice
From: carusogabriel34@gmail.com (Gabriel Caruso)

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Hi Levi, thanks for bringing this discussion.

Recently I've been scrutinizing array_slice. It's been painful.
>
> For instance, `$preserve_keys` is totally ignored for string keys.
> This was undocumented until Christoph integrated it 2-3 days ago
> (thanks, cmb). However, this is really not a good design decision: why
> have a parameter that is called `preserve_keys` if the data gets the
> final say, especially since there isn't any technical requirement for
> this?
>
> Here's another "fun" behavior: negative offsets whose absolute values
> are larger than the size of the array (eg the array has 3 elements and
> you pass an offset of -5) will shift the window to begin at zero
> instead of truncating the out-of-range values (which is what happens
> on the positive side).
>
> And another: `$length` is a length when it's a positive number, but
> it's an offset from the end when it's negative. You could perhaps
> convince me that when length is positive it's an offset from the
> `$offset` parameter. However, if you look at the design of slicing
> functions in other languages (eg Python, Ruby, JavaScript) they take
> beginning and ending offsets, not a beginning offset and a length.
>
> And another: it always iterates from the beginning of the array even
> if you are only interested in the last half (somewhat common for
> various algorithms that split things in half).
>
> Fixing `array_slice` would probably do more harm than good at this
> stage. Instead I would like to provide an alternative function that
> does not have all this baggage, and will have decent performance much
> of the time. The best ideas I have for names are not that great:
>
>   - `array_real_slice`?
>   - `array_slice2`?
>
> We could also split it into 2 functions, one that preserves keys and
> one that doesn't, instead of using a parameter. Any ideas there?
>
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A while ago I come up with this discussion in my Twitter, not with a new
function, but with a new "operator":
https://twitter.com/carusogabriel/status/974610078807613443

What do you think?

Thanks,

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