Edit report at https://bugs.php.net/bug.php?id=61787&edit=1
ID: 61787 Updated by: ras...@php.net Reported by: ubuntu at spacetrace dot org Summary: money_format round error Status: Not a bug Type: Bug Package: Math related Operating System: Linux ubuntu 11.04 PHP Version: 5.3.10 Block user comment: N Private report: N New Comment: Rounding errors compound when you loop like that. There is still no bug here. Previous Comments: ------------------------------------------------------------------------ [2012-04-21 21:21:40] ubuntu at spacetrace dot org now that i uderstand how floating numbers work in computers, this is sure a real bug then: they say: "a tiny error in the 17th decimal place doesnât matter at all " here the bug is at the 3rd place! and: " If you just donât want to see all those extra decimal places: simply format your result rounded to a fixed number of decimal places when displaying it." this is what i did here and that caused the bug think about it: NO ONE wants this behaviour if he or she uses '%.2i' in a function This function should be fixed, so it rounds mathematically correct like the round() function. If not, then it should throw an error like "cannot shorten a float variable with this syntax" or so. ------------------------------------------------------------------------ [2012-04-21 18:17:01] ras...@php.net How does always rounding down fix anything? What if you are trying to do 3.0 but you actually get 2.999999999999999, if you always round down you would get 2 instead of 3. ------------------------------------------------------------------------ [2012-04-21 17:28:38] ubuntu at spacetrace dot org ah ok, that explains the behaviour. wouldnt it be senseful, if php would always floor the float variable then? or at least throw a notice error, if you parse a float through "%.2i"? i understand this is not a senseful programm-style. cause you get an unpredictable behaviour. if money_format() would round down always, then it would be predictable are there more functions that would show the same behaviour like in this example? what about printf() ------------------------------------------------------------------------ [2012-04-21 14:59:48] ras...@php.net Did you visit the site we provided that explains this? What you think is 7.005 is actually represented as 7.004999999999999999 whereas 8.005 is 8.005000000000000000001 That's what limited precision means. Go read http://www.floating-point-gui.de/ for a complete explanation. ------------------------------------------------------------------------ [2012-04-21 10:11:02] ubuntu at spacetrace dot org so why does php round 7.005 down to 7.00 while it rounds 8.005 correctly up to 8.01 ? and why from 16 on again wrong and from 32 on again correct, from 64 on again wrong but now not a change from 128 on? ------------------------------------------------------------------------ The remainder of the comments for this report are too long. To view the rest of the comments, please view the bug report online at https://bugs.php.net/bug.php?id=61787 -- Edit this bug report at https://bugs.php.net/bug.php?id=61787&edit=1
