Unfortuantely, floating-point arithmetic in most CPUs and computer languages today is based on binary fractions (1/2, 1/4, 1/8, 1/16, ...) not decimal fractions (1/10, 1/100, 1/1000, 1/1000,...). There is no ActionScript Number (or C++ double) that is EXACTLY equal to 0.1, 0.2, or 0.3 because doing so would require an infinite number of binary fractional bits. (Some fractions such as 0.5 can be exactly represented because they only need a few binary fractional bits.) So you're pretty much always dealing with floating-point approximations to the real numbers that you think you're manipulating.
- Gordon From: [email protected] [mailto:[email protected]] On Behalf Of Chris Sent: Wednesday, November 25, 2009 5:17 PM To: [email protected] Subject: Re: [flexcoders] Re: When does 0.2 and 0.1 not equal 0.3? This is a pretty well known limitation of floating point numbers. A workaround: http://joshblog.net/2007/01/30/flash-floating-point-number-errors/ Another option around this is to use the toPrecision() function of Number/Int to convert a number to a String and then compare the Strings. var num1:Number = 0.1; var num2:Number = 0.2; var num3:Number = num1 + num2; trace("num3:"+num3); trace("is 0.3?"+(num3 == 0.3)); trace("num3.toPrecision()"+num3.toPrecision(3)); trace("is precise 0.3?"+(num3.toPrecision(3) == (0.3).toPrecision(3))); More info: http://www.google.com/search?q=floating+point+math+errors On Wed, Nov 25, 2009 at 5:11 PM, tntomek <[email protected]<mailto:[email protected]>> wrote: So to reliably add 0.1 and 0.2 I need to convert them to ints? This must be a joke, its not adding anything complicated. So is there a Flex wrapper for this? math.add(0.1, 0.2) ? How can we be sure that 2 numbers we just added equal the true sum? --- In [email protected]<mailto:flexcoders%40yahoogroups.com>, "kidl33t" <kidl...@...> wrote: > > I have encountered an odd bug. In the process of creating a little numeric > stepper component (a text box with an up/down stepper beside it) I have found > an odd rounding error. Starting from 0.0 and adding 0.1 increments, I get the > follow console output. > > currentNumber: 0 increment: 0.1 > result: 0.1 > > currentNumber: 0.1 increment: 0.1 > result: 0.2 > > currentNumber: 0.2 increment: 0.1 > result: 0.30000000000000004 > > As you can see, .2 + .1 is yielding 0.30000000000000004. This behaviour > happens at at many numbers actually. > > You can verify this yourself by simply doing a: trace( (0.1 + 0.2) ); > > The other flex developer at our company can also see this error, so I don't > think it's isolated to my box or particular build. Does anyone know anything > about this? >
