Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:72544
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain simon.geek.nz designates 103.6.213.4 as permitted sender)
Content-Type: text/plain; charset=windows-1252
Mime-Version: 1.0 (Mac OS X Mail 7.1 \(1827\))
In-Reply-To: <52FC4C8B.1040303@php.net>
Date: Thu, 13 Feb 2014 18:07:19 +1300
Cc: "internals@lists.php.net Internals" <internals@lists.php.net>,
 Yasuo Ohgaki <yohgaki@ohgaki.net>
Content-Transfer-Encoding: quoted-printable
Message-ID: <CF2F72B5-B99F-4F87-86D5-2BBFA706D1D6@simon.geek.nz>
References: <C8.81.19387.0D24CF25@pb1.pair.com> <CAGa2bXagisOuk6Fv83UbPy=KxE=oGp2WuW5Zg8yN7B==o35jCQ@mail.gmail.com> <52FC4C8B.1040303@php.net>
To: Davey Shafik <davey@php.net>
Subject: Re: [PHP-DEV] [RFC] Combined Comparison Operator
From: simon@simon.geek.nz (Simon J Welsh)

On 13/02/2014, at 17:39, Davey Shafik <davey@php.net> wrote:

> On 2/12/14, 11:25 PM, Yasuo Ohgaki wrote:
>> Hi Davey,
>>=20
>> On Thu, Feb 13, 2014 at 12:58 PM, Davey Shafik <davey@php.net> wrote:
>>=20
>>> I've written up an RFC/Patch to gauge interest and get feedback on =
the
>>> addition of a combined comparison (aka: spaceship) operator.
>>>=20
>>> You can see the RFC at: https://wiki.php.net/rfc/
>>> combined-comparison-operator
>>>=20
>>> This adds a new operator "(expr) <=3D> (expr)" that returns 0 if =
both
>>> operands are equal, 1 if the left is greater, and -1 if the right is
>>> greater.
>>>=20
>>> It works with all types (just as well as <, <=3D, >=3D, > work) and =
is great
>>> for usort() callbacks for example.
>>>=20
>>> Code available here (against 5.6): https://github.com/dshafik/
>>> php-src/compare/add-spaceship-operator
>>>=20
>>> I'd love to get this into 5.6, not sure if we hit feature freeze =
yet.
>>> Also, not sure if it needs 2/3 majority, but assumed so as pow did?
>>>=20
>>> Thoughts?
>>>=20
>>> If there is interest, I'll start adding tests. They should be fairly
>>> trivial.
>>>=20
>>=20
>> Interesting shortcut operator.
>> I feel closure function is for the task.
>> I would vote 0, but close to -1 since it's only useful for sorting.
>> Is there any other use cases?
>>=20
>> Regards,
>>=20
>> --
>> Yasuo Ohgaki
>> yohgaki@ohgaki.net
>>=20
>=20
> Yasuo,
>=20
> Sorting is definitely it's most compelling use. It cuts down on =
potentially quite a bit of code:
>=20
> function ($left, $right) {
>    if ($left[1] =3D=3D $right[1]) {
>         return 0;
>    }
>=20
>    if ($left[1] > $right[1]) {
>         return 1;
>    }
>=20
>    if ($left[1] < $right[1]) {
>        return -1;
>    }
> }
>=20
> or (as per the RFC):
>=20
> function ($left, $right) {
>    return $left[1] <=3D> $right[1];
> }
>=20
> --=20
> PHP Internals - PHP Runtime Development Mailing List
> To unsubscribe, visit: http://www.php.net/unsub.php

The only real case I see for this is to save some boilerplate when =
dealing with arrays. Strings have strcmp(), numbers have subtraction and =
when you=92re sorting objects, you probably want to be doing the =
comparison on some string/numeric property.

If you really need the -1/0/1 return value (sorting functions don=92t), =
then wrap the strcmp/subtraction in a trivial sign() function.
---
Simon Welsh
Admin of http://simon.geek.nz/