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Date: Wed, 11 Mar 2020 11:25:49 +0100
Message-ID: <CAF+90c-neSOtSoLHcjVd1eR55SK1kuMR+QQDC6t=9p+NwKc=fg@mail.gmail.com>
To: Andrea Faulds <ajf@ajf.me>
Cc: PHP internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary="000000000000efc80b05a091a940"
Subject: Re: [PHP-DEV] Make sorting stable
From: nikita.ppv@gmail.com (Nikita Popov)

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On Fri, Mar 6, 2020 at 12:58 AM Andrea Faulds <ajf@ajf.me> wrote:

> Hi,
>
> Nikita Popov wrote:
> >
> > I've implemented this variant now. If the comparison function returns a
> > boolean, you get
> >
> >> Deprecated: usort(): Returning bool from comparison function is
> > deprecated, return one of -1, 0 or 1 instead in %s on line %d
> >
> > once per usort() call, and we retry with swapped operands to ensure
> > compatibility.
> >
> > Regards,
> > Nikita
> >
>
> I think that message could be a little misleading, because any negative
> or positive value is valid, not just those of magnitude 1, right? IIRC
> strcmp($a, $b) doesn't just return -1 and 1, and of course this is also
> the case for the classic ($a - $b).
>

I've update the message to say:

> Deprecated: usort(): Returning bool from comparison function is
deprecated, return an integer less than, equal to, or larger than zero in
%s on line %d

The astute reader will notice that this is equivalent to "any integer", but
I think phrased this way, the meaning should be clear to anyone familiar
with the basic concept of comparison functions, while not mentioning -1, 0
and 1 in particular.

Regards,
Nikita

PS: Yes, I'm aware that you can also return a floating point number. No,
you should definitely not do that, because it's going to get casted to an
integer and produce wrong results if the numbers get large enough.

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