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Bug #37683 Comparison operator fails with certain numbers
Submitted: 2006-06-02 17:46 UTC Modified: 2006-06-02 18:07 UTC
From: jeb at webco dot tv Assigned:
Status: Not a bug Package: Math related
PHP Version: 5.1.4 OS: Linux / Ubuntu or Fedora
Private report: No CVE-ID: None
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 [2006-06-02 17:46 UTC] jeb at webco dot tv
Description:
------------
Code 1 listed below does not work as expected. Code 2 does. Interesting bug. If I replace the "<= 0.01" with "< 0.02", it does work as expected.

Reproduce code:
---------------
Code 1:
$data['low'] = 0.04;
$data['high'] = 0.05;

if ($data['high'] - $data['low'] <= 0.01)
	print "it works";

Code 2:
$data['low'] = 0.02;
$data['high'] = 0.03;

if ($data['high'] - $data['low'] <= 0.01)
	print "it works";

Expected result:
----------------
Both instances should print "it works."

Actual result:
--------------
Code 1 prints nothing.
Code 2 prints "it works".

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 [2006-06-02 18:07 UTC] mike@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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