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Bug #33644 sprintf digit formating problem
Submitted: 2005-07-11 14:54 UTC Modified: 2005-07-11 15:25 UTC
From: root at sunstation dot com Assigned:
Status: Not a bug Package: Unknown/Other Function
PHP Version: 4.3.11 OS: linux
Private report: No CVE-ID: None
View Developer Edit
 [2005-07-11 14:54 UTC] root at sunstation dot com 
Description:
------------
There is a problem with formatting float output for 0.28 values. Check it out.

Reproduce code:
---------------
<?php
for($i=1;$i<=10000;$i++)
  {
    $a = round($i/100,2);
    if (sprintf("%d",$a*100) != $i)
      echo sprintf("$i -> %d<br>",$a*100);
  }
?>

Expected result:
----------------
I would expect no output at all

Actual result:
--------------
29 -> 28
57 -> 56
58 -> 57
113 -> 112
114 -> 113
115 -> 114
116 -> 115
201 -> 200
203 -> 202
205 -> 204
207 -> 206
226 -> 225
228 -> 227
230 -> 229
232 -> 231
251 -> 250
253 -> 252
255 -> 254
402 -> 401
406 -> 405
410 -> 409
414 -> 413
427 -> 426
431 -> 430
435 -> 434
439 -> 438
452 -> 451
456 -> 455
460 -> 459
464 -> 463
477 -> 476
481 -> 480
485 -> 484
489 -> 488
...
...
8160 -> 8159
8171 -> 8170
8174 -> 8173
8182 -> 8181
8185 -> 8184

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 [2005-07-11 15:25 UTC] tony2001@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.

Hint:
<?php
var_dump((int)((29/100)*100));
?>
 
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