I do not know why Ceiling behave like in the below image
Why is processingFee != Settings.PaymentProcessingFeeInPercentage * prizesSum ?
alt text http://img514.imageshack.us/img514/3950/csharpceilingproblem.png
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I do not know why Ceiling behave like in the below image
Why is processingFee != Settings.PaymentProcessingFeeInPercentage * prizesSum ?
alt text http://img514.imageshack.us/img514/3950/csharpceilingproblem.png
Your percentage isn’t actually 0.05. It’s a value close to 0.05… and probably a little bit more than 0.05. Thus when it’s multiplied by 2600, you’re getting a value just over 130.0… which is then being “ceilinged” to 131.0.
Using a little tool I wrote a while ago (available from this page about .NET binary floating point types) it looks like the actual
floatvalue closest to 0.05 is 0.0500000007450580596923828125. For doubles, it’s 0.05000000000000000277555756156289135105907917022705078125.Moral of the story: don’t use
floatfor this sort of thing – usedecimal. Or if you’re just trying to represent a percentage, if it’s okay to actually be only accurate to one percent, use an integer value 0-100.