循环没有Do错误

Question

我正在尝试使用Excel VB实现一个简单的牛顿方法迭代求解器(我从未使用过VB.)

我一直收到错误loop without a Do,我无法弄清楚我在这里做错了什么.

我试图找到z^3 - z^2 - (B^2 + B - A)z - A*B称为压缩因子的函数的根.

我的来源MSN

Function zCalculation(ByVal temp As Double, ByVal press As Double) As Double

Dim tempCr As Double
Dim pressCr As Double
Dim A As Double
Dim B As Double

tempCr = temp / 238.5

pressCr = press / 547.424092

A = pressCr / tempCr
A = A / (9 * (2 ^ (1 / 3) - 1))
B = pressCr / tempCr
B = B * (2 ^ (1 / 3) - 1) / 3



Dim zNot As Double
Dim counter As Integer
counter = 0
zNot = 1#

Do
    counter = counter + 1

    zNot = zNot - (zNot ^ 3 - zNot ^ 2 - (B ^ 2 + B - A) * zNot - A * B) / (3 * zNot ^ 2 - 2 * zNot - (B ^ 2 + B - A))
    If counter > 1000 Then
       Exit Do

Loop Until eval(zNot, A, B) < 0.000001


zCalculation = zNot


End Function

打破

Function eval(ByVal z As Double, ByVal A As Double, ByVal B As Double) As Double

    eval = z ^ 3 - z ^ 2 - (B ^ 2 + B - A) * z - A * B

End Function

Answer 1

你需要一个:

End If

在你的代码中.