为什么99.99 / 100 = 0.9998999999999999 [英] Why does 99.99 / 100 = 0.9998999999999999

问题描述

可能重复：

处理浮点数的精度问题

99.99 * 0.01 = 0.99

很显然这是一个古老的浮点舍入问题，但是在这种情况下舍入误差对我来说似乎相当大;我的意思是我可能预期0.99990000001或类似的关闭结果的结果。

为了记录，我得到了同样的答案在一个JavaVM和一个.Net环境。
为什么0.9998999999999999不够贴近你（和0.9999000000000001是好的）？

abs（0.9999 - 0.9998999999999999）== abs（0.9999 - 0.9999000000000001）

Possible Duplicate:
Dealing with accuracy problems in floating-point numbers

Whereas 99.99 * 0.01 = 0.99

Clearly this is the age old floating point rounding issue, however the rounding error in this case seems quite large to me; what I mean is I might have expected a result of 0.99990000001 or some similar 'close' result.

And for the record I got the same answer in a JavaVM and in a .Net environment.

解决方案

Why 0.9998999999999999 is not close enough for you (and 0.9999000000000001 is good )?
abs(0.9999 - 0.9998999999999999) == abs (0.9999 - 0.9999000000000001)

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