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Bug #64350 fmod returning wrong values for negative dividends
Submitted: 2013-03-04 15:37 UTC Modified: 2013-03-04 15:59 UTC
From: spam at michaelburri dot ch Assigned:
Status: Not a bug Package: Math related
PHP Version: 5.4Git-2013-03-04 (Git) OS: OS X 10.8.2 (12C3012)
Private report: No CVE-ID: None
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From: spam at michaelburri dot ch
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 [2013-03-04 15:37 UTC] spam at michaelburri dot ch 
Description:
------------
The fmod(dividend, divisor) function returns wrong values for negative dividends 
that are smaller than the divisor.

For example -0.8 mod 6 => -1 * 6 + 5.2, so the result of the modulo (= remainder) 
is 5.2.

Test script:
---------------
<?php
  echo fmod(-0.8, 6); //Should return 5.2, but returns -0.8
?>

Expected result:
----------------
5.2

Actual result:
--------------
-0.8

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 [2013-03-04 15:59 UTC] rasmus@php.net 
Nope, it is correct. Read up on fmod and negative operands and you can try this 
simple C program:

void main(int argc, char *argv[]) {
  printf("%f", fmod(-0.8,6));
}
 [2013-03-04 15:59 UTC] rasmus@php.net
-Status: Open +Status: Not a bug
 
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