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Date: Tue, 31 May 2011 23:41:36 +0200
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To: Julien Pauli <jpauli@php.net>, internals@lists.php.net
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Subject: Re: [PHP-DEV] INF behavior
From: landeholm@gmail.com (Hannes Landeholm)

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> Agree with Derick, strictly speaking, in maths science, INF != INF.

I disagree,based on quote from
http://compilers.iecc.com/comparch/article/98-07-134:

"Since a projective infinity doesn't have a sign, comparing a floating point
value other than infinity to a projective infinity is unordered. However, a
projective infinity is equal to itself."

Hannes


On 31 May 2011 21:39, Julien Pauli <jpauli@php.net> wrote:

> Agree with Derick, strictly speaking, in maths science, INF != INF.
>
> But I dont care if PHP tells me than yes, because PHP is not designed
> to solve high level maths problems :)
>
> Cheer,
>
> Julien.Pauli
>
> On Fri, May 27, 2011 at 4:48 PM, Derick Rethans <derick@php.net> wrote:
> > On Thu, 26 May 2011, Scott MacVicar wrote:
> >
> >> On 26 May 2011, at 20:03, Philip Olson <philip@roshambo.org> wrote:
> >>
> >> > Hello geeks,
> >> >
> >> > A geek is needed to clarify PHP bug #45712. This is an edge case but
> the test (bug45712.phpt) contains code similar to the following:
> >> >
> >> > <?php
> >> > $inf = pow(0, -2);
> >> >
> >> > var_dump($inf);          // float(INF)
> >> > var_dump($inf ==  $inf); // bool(false)
> >> > var_dump($inf === $inf); // bool(true)
> >> > ?>
> >> >
> >> > That's how it's behaved since ~forever (AFAICT) and remains in
> 5.3.7-dev, but PHP 5.4.0-dev changes behavior so both now return true.
> >> >
> >> > Is this is how we want it? And how should this be
> documented/explained?
> >>
> >> I think I changes this :-)
> >>
> >> It didn't make sense that == and === produce different results.
> >>
> >> Though if someone has a better understanding of maths then we can fix
> it.
> >
> > I think it does make sense. == is the equal operator, and INF is not
> > equal to INF (just like SQL NULL is not equal to NULL). However, they
> > are identical (like you can test in SQL with NULL IS NULL).
> >
> > cheers,
> > Derick
> >
> > --
> > http://derickrethans.nl | http://xdebug.org
> > Like Xdebug? Consider a donation: http://xdebug.org/donate.php
> > twitter: @derickr and @xdebug
> >
> > --
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> >
> >
>
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