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Bug #53972 Operator Type Casting Issue
Submitted: 2011-02-09 13:56 UTC Modified: 2011-02-10 19:30 UTC
From: thipse_rahul at rediffmail dot com Assigned:
Status: Not a bug Package: *General Issues
PHP Version: 5.3.5 OS: Linux/Windows
Private report: No CVE-ID: None
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 [2011-02-09 13:56 UTC] thipse_rahul at rediffmail dot com 
Description:
------------
Following code snippet -- 

Case 1:
$a = (int)((0.1+0.7) * 10); echo $a; // Result: 7 (Wrong) should give 8 

Case 2:
$a = (int)((0.1+0.6) * 10); echo $a; // Result: 7
Case 3:
$a = (int)((0.1+0.8) * 10); echo $a; // Result: 9


Test script:
---------------
$a = (int)((0.1+0.7) * 10); 
echo $a;




Expected result:
----------------
8

Actual result:
--------------
7

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 [2011-02-09 14:18 UTC] johannes@php.net
-Status: Open +Status: Bogus
 [2011-02-09 14:18 UTC] johannes@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.

.
 [2011-02-09 17:43 UTC] anon at anon dot anon 
PHP guys, will you please stop giving people broken links?
 [2011-02-10 05:16 UTC] thipse_rahul at rediffmail dot com 
Thanks for reply johannes 

Yes I agree for float, 
Then Whey Case(2) & Case(3) gives wrong result.
Case 2:
$a = (int)((0.1+0.6) * 10); echo $a; // Act.Result: 7  // Exp. : 6
Case 3:
$a = (int)((0.1+0.8) * 10); echo $a; // Act.Result: 9  // Exp.: 8 

Hope you will give satisfactory feedback.

Thanks!
 [2011-02-10 19:30 UTC] johannes@php.net 
0.1+0.9 is not exactly 1 but a tiny bit less. (int) rounds down.
 
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