Req->Doc #60346 [ReO->Opn]: NAN != NAN

Edit report at https://bugs.php.net/bug.php?id=60346&edit=1 ID: 60346 Updated by: cataphract@php.net Reported by: yunosh@php.net Summary: NAN != NAN -Status: Re-Opened +Status: Open -Type: Feature/Change Request +Type: Documentation Problem Package: Documentation problem Operating System: Linux PHP Version: 5.4.0RC1 Block user comment: N Private report: N New Comment: 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 Previous Comments: ------------------------------------------------------------------------ [2011-11-21 14:32:30] 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 13:50:32] 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 13:02:27] 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 12:58:03] 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 11:16:44] 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 ------------------------------------------------------------------------ The remainder of the comments for this report are too long. To view the rest of the comments, please view the bug report online at https://bugs.php.net/bug.php?id=60346 -- Edit this bug report at https://bugs.php.net/bug.php?id=60346&edit=1