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Bug #47389 With a for, after a while it miscounts.
Submitted: 2009-02-14 20:57 UTC Modified: 2009-02-14 23:49 UTC
Votes:1
Avg. Score:2.0 ± 0.0
Reproduced:1 of 1 (100.0%)
Same Version:1 (100.0%)
Same OS:1 (100.0%)
From: php at mycel dot nl Assigned:
Status: Not a bug Package: Variables related
PHP Version: 5.2.9RC2 OS: Ubuntu
Private report: No CVE-ID: None
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 [2009-02-14 20:57 UTC] php at mycel dot nl 
Description:
------------
With a for, if you count to 100, it will miscounts after a while.

(with other computers it wil miscount earlier)

Reproduce code:
---------------
for ($i = 0; $i <= 800; $i += 0.01)
{
echo $i.'<br/>';
}

Expected result:
----------------
709.23
709.24
709.25
709.26
709.27
709.28
709.29

Actual result:
--------------
709.23
709.24
709.25
709.259999999
709.269999999
709.279999999
709.289999999

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 [2009-02-14 23:49 UTC] jani@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.

If you would like to know more about "floats" and what IEEE
754 is, read this:
http://docs.sun.com/source/806-3568/ncg_goldberg.html
 
Thank you for your interest in PHP.
 
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