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Date: Fri, 12 Jul 2024 15:24:00 +0200
To: internals@lists.php.net
Subject: Re: [PHP-DEV] Breaking change of rounding behavior in PHP 8.4
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From: rob@bottled.codes ("Rob Landers")

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On Fri, Jul 12, 2024, at 13:24, Christoph M. Becker wrote:
> Hi all,
>=20
> there has been a "small" change in the rounding logic of
> _php_math_round()[1] a couple of months ago.  A respective ticket,
> claiming the new behavior would be a bug[2] had been filed a while ago
> without proper triage so far.  I'm bringing this to your attention,
> because I'm afraid that there will be (many) more bug reports about th=
is
> in the future (note that the change only affects master, and only PHP
> 8.4.0alpha1 has been released yet, so it is probably not widespreadly
> tested yet).  At the very least we should be sure that we want to keep
> this change, and document it well, to avoid discussions in every filed
> ticket.
>=20
> My personal stance on this is simple: floating point arithmetic is not
> exact per se, and changes to how PHP handles the details should only be
> introduced, if they clearly improve things.  This change apparently
> improves some cases, but worsens others.  Thus, I think the change
> should better be reverted, and if at all, postponed to PHP 9, since I
> neither regard this change as bug fix nor as a feature.
>=20
> What do you think?
>=20
> [1] <https://github.com/php/php-src/pull/12222>
> [2] <https://github.com/php/php-src/issues/14332>
>=20
> Cheers,
> Christoph
>=20

I guess the real question is: how many of these numbers should be the sa=
me?

https://3v4l.org/tgRMc/rfc#vgit.master

=E2=80=94 Rob
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<!DOCTYPE html><html><head><title></title><style type=3D"text/css">p.Mso=
Normal,p.MsoNoSpacing{margin:0}</style></head><body><div>On Fri, Jul 12,=
 2024, at 13:24, Christoph M. Becker wrote:<br></div><blockquote type=3D=
"cite" id=3D"qt" style=3D""><div>Hi all,<br></div><div><br></div><div>th=
ere has been a "small" change in the rounding logic of<br></div><div>_ph=
p_math_round()[1] a couple of months ago.&nbsp; A respective ticket,<br>=
</div><div>claiming the new behavior would be a bug[2] had been filed a =
while ago<br></div><div>without proper triage so far.&nbsp; I'm bringing=
 this to your attention,<br></div><div>because I'm afraid that there wil=
l be (many) more bug reports about this<br></div><div>in the future (not=
e that the change only affects master, and only PHP<br></div><div>8.4.0a=
lpha1 has been released yet, so it is probably not widespreadly<br></div=
><div>tested yet).&nbsp; At the very least we should be sure that we wan=
t to keep<br></div><div>this change, and document it well, to avoid disc=
ussions in every filed<br></div><div>ticket.<br></div><div><br></div><di=
v>My personal stance on this is simple: floating point arithmetic is not=
<br></div><div>exact per se, and changes to how PHP handles the details =
should only be<br></div><div>introduced, if they clearly improve things.=
&nbsp; This change apparently<br></div><div>improves some cases, but wor=
sens others.&nbsp; Thus, I think the change<br></div><div>should better =
be reverted, and if at all, postponed to PHP 9, since I<br></div><div>ne=
ither regard this change as bug fix nor as a feature.<br></div><div><br>=
</div><div>What do you think?<br></div><div><br></div><div>[1] &lt;<a hr=
ef=3D"https://github.com/php/php-src/pull/12222">https://github.com/php/=
php-src/pull/12222</a>&gt;<br></div><div>[2] &lt;<a href=3D"https://gith=
ub.com/php/php-src/issues/14332">https://github.com/php/php-src/issues/1=
4332</a>&gt;<br></div><div><br></div><div>Cheers,<br></div><div>Christop=
h<br></div><div><br></div></blockquote><div><br></div><div>I guess the r=
eal question is: how many of these numbers should be the same?<br></div>=
<div><br></div><div><a href=3D"https://3v4l.org/tgRMc/rfc#vgit.master">h=
ttps://3v4l.org/tgRMc/rfc#vgit.master</a><br></div><div><br></div><div i=
d=3D"sig121229152">=E2=80=94 Rob<br></div></body></html>
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