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Bug #31870 rounding negative numbers gives "-0"
Submitted: 2005-02-07 13:08 UTC Modified: 2005-02-08 14:19 UTC
From: amir at foresthc dot com Assigned:
Status: Not a bug Package: *General Issues
PHP Version: 5.0.3 OS: Debian woody
Private report: No CVE-ID: None
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 [2005-02-07 13:08 UTC] amir at foresthc dot com 
Description:
------------
When rounding real negative numbers that should round to zero, the result is -0 (minus zero). This isn't a critical bug, but it's a nusanse hunting these down in places were the output reaches the user.

Reproduce code:
---------------
echo round(-0.1);

Expected result:
----------------
0

Actual result:
--------------
-0

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 [2005-02-07 13:41 UTC] derick@php.net 
Floating point values have a limited precision. Hence a value might 
not have the same string representation after any processing. That also
includes writing a floating point value in your script and directly 
printing it without any mathematical operations.
 
Thank you for your interest in PHP.

.
 [2005-02-07 13:57 UTC] amir at foresthc dot com 
I was under the impression that zero has a unique floating point representation, and the only problem is with the sign flag.

Also the case at hand is not of "any mathematical operations" but of call to a mathematical function, and I am assuming there is one common piece of internal code that round() / number_format() / *printf() all use.

Obviously having no familiarity with PHP's internal code my assumptions could be completely incorrect.
 [2005-02-08 14:09 UTC] amir at foresthc dot com 
re-opened to get a reponse.
 [2005-02-08 14:19 UTC] derick@php.net 
This is not a discussion forum, and we just use the underlying  glibc.
 
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