Double型相减的问题

[lywei123]

Private Sub Command2_Click()
Dim a As Double

Dim LdNum1 As Double
Dim LdNum2 As Double

LdNum1 = 11111111.1

LdNum2 = 11111111

a = LdNum1 - LdNum2

End Sub

请问怎么才能让a = 0.1 呢？如果a可能有4位以上的小数时呢？

[ZWB_ZYN]

round函数

Private Sub Command2_Click()
Dim a As Double

Dim LdNum1 As Double
Dim LdNum2 As Double

LdNum1 = 11111111.1

LdNum2 = 11111111

a = round((LdNum1 - LdNum2),1)

End Sub

[xmuyyd]

Private Sub Command2_Click()
Dim a As Double

Dim LdNum1 As Double
Dim LdNum2 As Double

LdNum1 = 11111111.1

LdNum2 = 11111111

a = format((LdNum1 - LdNum2),"0.0")

End Sub

[viena]

浮点运算不精确，除非小数部分是2的N次方分之一的和

[viena]

计算机的数是二进制存储的
十进制有限小数，转为二进制可能就是无限小数

[viena]

二存储位数是有限的，要舍去后面部分，必然会产生结果误差~

[viena]

要使运算精确，最好用定点类型
可以用Currency，64位定点数，是精确的，但最多只能有4位小数

[viena]

用Currency最多只能有4位小数，假设有6位小数的话，可以把这个数看作是实际值的100倍