ID: 42333 Updated by: [EMAIL PROTECTED] Reported By: boydell at orbsix dot com -Status: Open +Status: Bogus Bug Type: Math related Operating System: WinXP, Linux PHP Version: 5.2.3 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. Previous Comments: ------------------------------------------------------------------------ [2007-08-18 00:14:20] boydell at orbsix dot com Description: ------------ The math on the following should be zero. echo (65 + 50 - 50 + 15 - 15 + 100 - 100 + 50 + 16.50 - 36.50 + 88.21 - 38.21 - 145); but we get: -2.84217094304E-14 Reproduce code: --------------- $list = array(65, 50, -50, 15, -15, 100, -100, 50, 16.50, -36.50, 88.21, -38.21, -145); $current = 0; foreach($list as $number) { echo $current . "+" . $number . "="; $current += $number; echo $current . "\n<br>"; } Expected result: ---------------- 0+65=65 65+50=115 115+-50=65 65+15=80 80+-15=65 65+100=165 165+-100=65 65+50=115 115+16.5=131.5 131.5+-36.5=95 95+88.21=183.21 183.21+-38.21=145 145+-145=0 Actual result: -------------- 0+65=65 65+50=115 115+-50=65 65+15=80 80+-15=65 65+100=165 165+-100=65 65+50=115 115+16.5=131.5 131.5+-36.5=95 95+88.21=183.21 183.21+-38.21=145 145+-145=-2.8421709430404E-14 ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=42333&edit=1
