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Date: Wed, 20 Aug 2014 17:31:26 +0800
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To: =?UTF-8?Q?Johannes_Schl=C3=BCter?= <johannes@schlueters.de>
Cc: Marc Bennewitz <php@mabe.berlin>, Sara Golemon <pollita@php.net>, 
	PHP internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=047d7bb04dd2a3155a05010c444c
Subject: Re: [PHP-DEV] [RFC] Binary String Comparison
From: tjerk.meesters@gmail.com (Tjerk Meesters)

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On Tue, Aug 19, 2014 at 11:07 AM, Tjerk Meesters <tjerk.meesters@gmail.com>
wrote:

>
> On Mon, Aug 18, 2014 at 11:30 PM, Johannes Schl=C3=BCter <
> johannes@schlueters.de> wrote:
>
>> On Mon, 2014-08-18 at 23:09 +0800, Tjerk Meesters wrote:
>> > > On 18 Aug, 2014, at 10:47 pm, Johannes Schl=C3=BCter <
>> johannes@schlueters.de> wrote:
>> > >
>> > >> On Mon, 2014-08-18 at 14:44 +0200, Marc Bennewitz wrote:
>> > >> The question isn't "What's wrong with =3D=3D=3D, strcmp()?" but "Wh=
at's
>> wrong
>> > >> with =3D=3D, <, >?".
>> > >>
>> > >> We have a standard way to compare two operands but currently we do
>> some
>> > >> magic things to solve something that don't need to be solved.
>> > >
>> > > Still it is a key property of the language which we can't simply
>> change.
>> > > Also mind this: All input data are strings and some databases also
>> > > return data as string. So code like
>> > >
>> > >   if ($_GET['id'] > 0)
>> > > or
>> > >   if ($db->fetchRow()[0] =3D=3D 12)
>> > >
>> > > which is common will break.
>> >
>> > Those two cases will actually not be affected, it's strictly
>> string<=3D>string comparisons that's being discussed here.
>>
>> Meaning that simple code you find everywhere, in every second tutorial
>>
>>    foreach ($db->query("SELECT id, title FROM entries") as $row) {
>>        echo "<tr><td";
>>        if ($row[0] =3D=3D $_GET['highlight_id']) {
>>            echo " background=3D'#ff0000'";
>>        }
>>        echo ">".htmlentities($row[1])."</td></tr>";
>>    }
>>
>> will suddenly fail. How wonderful! (irony)
>>
>
> Not necessarily and certainly not by definition; reasons for failure are
> less obvious such as (but not limited to):
>
> "0" =3D=3D "0.0"
> "11" =3D=3D " 11" (but note that "11" =3D=3D "11 " currently yields false=
)
> "0" =3D=3D ""
>

I had mistakenly assumed that "0" =3D=3D "" would currently yield true, but=
 it
doesn't. My apologies for that. The other two statements are still valid,
though. So are these:

"0" =3D=3D "0x0"
"0" =3D=3D "00"


> I'm not arguing for or against this behaviour change, but I found it
> necessary to clear up some apparent confusion as to what repercussions th=
is
> proposal carries.
>
> Another approach of attempting to solve the common issue of comparing big
> numbers with '=3D=3D' is to only enforce string-wise comparison if a numb=
er
> cast would cause precision loss.
>
>
>> johannes
>>
>> ps. yes, the example might be done nicer and better, it still represents
>> a common pattern.
>>
>>
>
>
> --
> --
> Tjerk
>



--=20
--
Tjerk

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