Bug #74534 [Opn->Nab]: 123
Edit report at https://bugs.php.net/bug.php?id=74534&edit=1
ID: 74534
Updated by: requinix@php.net
Reported by: uchihasv at yandex dot ru
Summary: 123
-Status: Open
+Status: Not a bug
Type: Bug
Package: *General Issues
Operating System: Windows 7 x64
PHP Version: 7.1.4
Block user comment: N
Private report: N
New Comment:
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.
Previous Comments:
------------------------------------------------------------------------
[2017-05-03 10:56:50] uchihasv at yandex dot ru
Description:
------------
I have array with numbers and i do simple math in loop and in results i see -6.9388939039072E-17
instead 0
Test script:
---------------
<?php
$h = 0.05;
$x = [-1,-0.5,0,0.5,1];
for($i=0;$i<4;$i++)
{
for($j=$x[$i]+$h;$j<$x[$i+1];$j+=$h)
{
$x2[$i][] = $j;
}
}
echo "<pre>".print_r($x2,1)."</pre>";
Expected result:
----------------
Array
(
[0] => Array
(
[0] => -0.95
[1] => -0.9
[2] => -0.85
[3] => -0.8
[4] => -0.75
[5] => -0.7
[6] => -0.65
[7] => -0.6
[8] => -0.55
)
[1] => Array
(
[0] => -0.45
[1] => -0.4
[2] => -0.35
[3] => -0.3
[4] => -0.25
[5] => -0.2
[6] => -0.15
[7] => -0.1
[8] => -0.05
[9] => 0
)
[2] => Array
(
[0] => 0.05
[1] => 0.1
[2] => 0.15
[3] => 0.2
[4] => 0.25
[5] => 0.3
[6] => 0.35
[7] => 0.4
[8] => 0.45
[9] => 0.5
)
[3] => Array
(
[0] => 0.55
[1] => 0.6
[2] => 0.65
[3] => 0.7
[4] => 0.75
[5] => 0.8
[6] => 0.85
[7] => 0.9
[8] => 0.95
)
)
Actual result:
--------------
Array
(
[0] => Array
(
[0] => -0.95
[1] => -0.9
[2] => -0.85
[3] => -0.8
[4] => -0.75
[5] => -0.7
[6] => -0.65
[7] => -0.6
[8] => -0.55
)
[1] => Array
(
[0] => -0.45
[1] => -0.4
[2] => -0.35
[3] => -0.3
[4] => -0.25
[5] => -0.2
[6] => -0.15
[7] => -0.1
[8] => -0.05
[9] => -6.9388939039072E-17
)
[2] => Array
(
[0] => 0.05
[1] => 0.1
[2] => 0.15
[3] => 0.2
[4] => 0.25
[5] => 0.3
[6] => 0.35
[7] => 0.4
[8] => 0.45
[9] => 0.5
)
[3] => Array
(
[0] => 0.55
[1] => 0.6
[2] => 0.65
[3] => 0.7
[4] => 0.75
[5] => 0.8
[6] => 0.85
[7] => 0.9
[8] => 0.95
)
)
------------------------------------------------------------------------
--
Edit this bug report at https://bugs.php.net/bug.php?id=74534&edit=1
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