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Bug #19398 mathmatical errors, especially after string conversions
Submitted: 2002-09-13 20:03 UTC Modified: 2002-09-17 04:43 UTC
Votes:1
Avg. Score:5.0 ± 0.0
Reproduced:1 of 1 (100.0%)
Same Version:1 (100.0%)
Same OS:1 (100.0%)
From: jeffb at umci dot com Assigned:
Status: Not a bug Package: Scripting Engine problem
PHP Version: 4.2.2 OS: Redhat 7.3
Private report: No CVE-ID: None
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From: jeffb at umci dot com
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 [2002-09-13 20:03 UTC] jeffb at umci dot com
The script below produces a lot of output on two of 
our systems. One a 6 cpu ppro, the other a single
cpu duron 950. Both boxes run redhat 7.3. One runs the
php that came with redhat 7.3, the 6 cpu box runs php
4.2.2 that we compiled ourselves to add more options.

For sample output of this script, with a phpinfo() call
appended to it, go to:

http://www.umci.com/testcode.phtml


<?
$start=0.01;
while ($start <= 10) {
// Removing the quotes from test's assignment will eliminate the 
// errors unless you uncomment the ++/-- down a fiew lines.
$test="$start";
$test2=$start;

/////////////////////////////////////////////////////////////////
// Uncommenting these two lines accentuates the problem a bit...
/////////////////////////////////////////////////////////////////
//$test++;
//$test--;

if ($test!=$test2)
echo "Comparison Result: \"$test\" != \"$test2\" ----- Shouldn't this be true?<br>";
$start = $start + 0.01;
} 

?>

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 [2002-09-17 04:43 UTC] hholzgra@php.net
Never compare floats for equalness!

Thats like comparing two pieces of rope
for exactly equal length -> you won't 
ever find an equal pair

see for example the note on http://www.php.net/language.types.float
 
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