#39464 [Opn->Bgs]: Range function produces odd values in foreach loop

ID: 39464 Updated by: tony2001@php.net Reported By: netnessie at gmail dot com -Status: Open +Status: Bogus Bug Type: *Programming Data Structures Operating System: Linux PHP Version: 5.2.0 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://docs.sun.com/source/806-3568/ncg_goldberg.html Thank you for your interest in PHP. Yes, the result of (1 - (float)1) might look like float(-2.2204460492503E-16), because that's how modern computers work with float numbers. Previous Comments: ------------------------------------------------------------------------ [2006-11-10 15:25:00] netnessie at gmail dot com Description: ------------ When you use the range function, with a range between zero and 1, incrementing by 0.05 each step, the loop produces an incorrect result when you attempt to minus the current value in the loop from 1. As you can see below, the last element in the array is the integer 1. The script should echo the result of 1 minus 1. However, for some reason PHP treats 1-1 as -2.22044604925E-16 instead of zero. Reproduce code: --------------- foreach (range(0,1,0.05) as $t) { echo (1-$t).'<br />'; } Expected result: ---------------- 1 0.95 0.9 0.85 0.8 0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Actual result: -------------- 1 0.95 0.9 0.85 0.8 0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 -2.22044604925E-16 ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=39464&edit=1