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Bug #55720 *printf problem formatting numbers
Submitted: 2011-09-18 15:28 UTC Modified: 2011-09-18 15:31 UTC
From: php_nospam at ramihyn dot sytes dot net Assigned:
Status: Not a bug Package: Scripting Engine problem
PHP Version: Irrelevant OS: any
Private report: No CVE-ID: None
View Developer Edit
 [2011-09-18 15:28 UTC] php_nospam at ramihyn dot sytes dot net 
Description:
------------
*printf functions have a problem correctly formatting numbers

Problem is reproducible with php 5.3.8 (win32) and php 5.3.6 (linux x86).
Numbers output were different on my two machines, but stayed the same on each machine.

Test script:
---------------
<?php
printf("%0.31f %0.31f %0.31f",
  3.14159265359793238462643383279,
  14159265359793238462643383279.0,
  1.3
);
?>

Expected result:
----------------
3.1415926535979323846264338327900 14159265359793238462643383279.0000000000000000000000000000000 1.3000000000000000000000000000000

Actual result:
--------------
3.1415926535979323830360954161733 14159265359793237514732437504.0000000000000000000000000000000 1.3000000000000000444089209850063

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 [2011-09-18 15:31 UTC] pajoye@php.net
-Status: Open +Status: Bogus
 [2011-09-18 15:31 UTC] pajoye@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://www.floating-point-gui.de/

Thank you for your interest in PHP.
 
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