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Doc Bug #60346 NAN != NAN
Submitted: 2011-11-21 10:15 UTC Modified: 2011-12-03 19:25 UTC
From: yunosh@php.net Assigned: frozenfire (profile)
Status: Closed Package: Documentation problem
PHP Version: 5.4.0RC1 OS: Linux
Private report: No CVE-ID: None
View Developer Edit
 [2011-11-21 10:15 UTC] yunosh@php.net 
Description:
------------
This is a regression from PHP 5.3.

Test script:
---------------
var_dump(NAN == NAN);

Expected result:
----------------
bool(true)

Actual result:
--------------
bool(false)

Patches

Pull Requests

History

AllCommentsChangesGit/SVN commitsRelated reports
 [2011-11-21 11:16 UTC] laruence@php.net 
Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php

"x = x returning false can be used to test if x is a quiet NaN"
see: http://en.wikipedia.org/wiki/NaN
 [2011-11-21 11:16 UTC] laruence@php.net
-Status: Open +Status: Bogus
 [2011-11-21 12:58 UTC] yunosh@php.net 
It's not documented (http://www.php.net/manual/en/math.constants.php) and it's still a regression that isn't documented either: http://php.net/releases/NEWS_5_4_0_RC1.txt
 [2011-11-21 12:58 UTC] yunosh@php.net
-Status: Bogus +Status: Re-Opened
 [2011-11-21 13:02 UTC] laruence@php.net 
what do you mean by regression ?
I have tested in PHP 5.2.14, the same output as PHP 5.4
 [2011-11-21 13:50 UTC] yunosh@php.net 
You are right. I tracked a failing unit test with PHP 5.4.0RC down the wrong code path. The regression is in a different place.

In PHP 5.3
abs(NAN - NAN) <= 0
evaluates to true, in PHP 5.4 it evaluates to false.

And if you wonder where this strange code is coming from:
https://github.com/sebastianbergmann/phpunit/blob/3.5/PHPUnit/Framework/Constraint/IsEqual.php#L363
This seems to have been worked around in later PHPUnit versions though.
 [2011-11-21 14:32 UTC] laruence@php.net 
I think NAN - NAN is undefined behavior, so you should not rely on such 
statements.

and I will mark this as a doc request, which request to explain the NAN's 
features. :)
 [2011-11-21 14:32 UTC] laruence@php.net
-Type: Bug +Type: Feature/Change Request -Package: Scripting Engine problem +Package: Documentation problem
 [2011-11-21 20:10 UTC] cataphract@php.net
-Status: Re-Opened +Status: Open -Type: Feature/Change Request +Type: Documentation Problem
 [2011-11-21 20:10 UTC] cataphract@php.net 
Thank you for the report, but this has already been discussed and 5.4's behavior follows IEEE 754-2008.

See http://marc.info/?l=php-internals&m=130649054107748
 [2011-12-03 06:14 UTC] frozenfire@php.net
-Status: Open +Status: Assigned -Assigned To: +Assigned To: frozenfire
 [2011-12-03 06:14 UTC] frozenfire@php.net 
My intention is to document NaN in the float type document, as a subsection. I'll 
make mention of the spec behaviour.
 [2011-12-03 19:25 UTC] frozenfire@php.net 
This bug has been fixed in the documentation's XML sources. Since the
online and downloadable versions of the documentation need some time
to get updated, we would like to ask you to be a bit patient.

Thank you for the report, and for helping us make our documentation better.

Master was down during commit, so the fix was revision 320310.
 [2011-12-03 19:25 UTC] frozenfire@php.net
-Status: Assigned +Status: Closed
 
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