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Date: Tue, 19 Aug 2014 11:07:59 +0800
Message-ID: <CAHMUw2E_RxxbBfCyZmSPqhzwTdvHueqCJT9=3=m87t0BTHGNEw@mail.gmail.com>
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=089e013d16f0816f950500f2cb23
Subject: Re: [PHP-DEV] [RFC] Binary String Comparison
From: tjerk.meesters@gmail.com (Tjerk Meesters)

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On Mon, Aug 18, 2014 at 11:30 PM, Johannes Schl=C3=BCter <johannes@schluete=
rs.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 "Wha=
t'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'm not arguing for or against this behaviour change, but I found it
necessary to clear up some apparent confusion as to what repercussions this
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 number
cast would cause precision loss.


> johannes
>
> ps. yes, the example might be done nicer and better, it still represents
> a common pattern.
>
>


--=20
--
Tjerk

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