为什么在VBA访问134.605 * 100不等于13460.5？ [英] Why is 134.605*100 not equal 13460.5 in VBA Access?

问题描述

我想这事做的precision，但我不明白。我有这块code，应该进行舍入到2位（值的是输入）：

I guess it has something to do with the precision but I don't understand it. I have this piece of code that should perform rounding to 2 places (value is the input):

Dim a As Double
Dim b As Double
Dim c As Double
Dim result As Double

a = CDbl(value) * 100
b = a + 0.5 //because Int in the next line performs floor operation, 0.5 is added to ensure proper rounding, example for 123.5: Int(123.5) = 123 but we need Int(123.5 + 0.5) = 124
c = Int(b)
result = c / 100

的事情是，它不正确的值134.605的工作。在调试我发现，一个值计算不正确。 其实我已经检查了这一点：

The thing is, it doesn't work properly for a value 134.605. While debugging I found out that a value is calculated incorrectly. In fact I have checked this:

?13460.5 = (134.605*100)
False
?(134.605*100) - 13460.5
-1,02318153949454E-12

和我被困。我可以重写四舍五入的功能有所不同，但我不无* 100乘有一个想法吧。或者，我可以找出如何使* 100的操作正确地工作，为所有的值。任何人都可以尝试，为什么它发生在我解释，并提出一个解决方案？

And I'm stuck. I can either rewrite the rounding function differently, but I don't have an idea for it without *100 multiplication. Or I could find out how to make *100 operation work correctly for all the values. Could anyone try to explain me why it happens and suggest a solution?

推荐答案

尝试十进制的数据类型。虽然不能明确地声明这种类型的变量，你可以含蓄地声明为变式并使用转换 CDEC 。

Try Decimal data type. Although you cannot explicitly declare a variable of this type, you can convert it to such implicitly by declaring it as Variant and converting using CDec.

Debug.Print 13460.5 = CDec(134.605 * 100) 'Output - True

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