确定实际传递给VBA函数的多少（可选）参数？

I'd like to define a function in Visual Basic which computes income tax in a given bracket. The inputs should be the income, the marginal tax rate, the lower bracket boundary, and - optionally - the upper bracket boundary. (For the top bracket there is no upper boundary).

我想在Visual Basic中定义一个函数，它在给定的括号中计算所得税。输入应该是收入，边际税率，下括号边界，以及 - 可选 - 上括号边界。（对于顶部支架，没有上边界）。

Here's how I went about it. First, I define a "ramp" function as follows:

这是我如何去做的。首先，我定义一个“斜坡”函数如下：

Public Function ramp(x)
    ramp = (x + Abs(x)) / 2
End Function

which is basically the same as IF(x<0,0,x). Then I define the function (in Dutch) for the tax as

这基本上与IF（x <0,0，x）相同。然后我定义税收的函数（荷兰语）

Public Function schijfbelasting(inkomen, ondergrens, bovengrens, tarief)
    schijfbelasting = ramp(tarief * (inkomen - ondergrens)) - ramp(tarief * (inkomen - bovengrens))
End Function

Here "inkomen"=income, "ondergrens"=lower bracket boundary, "bovengrens"=upper bracket boundary, "tarief"=marginal tax rate, and the output "schijfbelasting"=tax in the specified bracket.

这里“inkomen”=收入，“ondergrens”=下括号边界，“bovengrens”=上括号边界，“tarief”=边际税率，输出“schijfbelasting”=指定括号中的税。

This all works fine, except that I'd like to make the "bovengrens" (upper bracket boundary) optional using

这一切都很好，除了我想使用“bovengrens”（上括号边界）可选

Optional bovengrens

In Matlab, I would use the "nargin" (number of arguments) function to do something like the following:

在Matlab中，我会使用“nargin”（参数个数）函数来执行以下操作：

Public Function schijfbelasting(inkomen, ondergrens, Optional bovengrens, tarief)
If nargin==4
    schijfbelasting = ramp(tarief * (inkomen - ondergrens)) - ramp(tarief * (inkomen - bovengrens))
Elseif nargin==3
schijfbelasting = ramp(tarief*(inkomen-ondergrens))
End If
End Function

However, I'm not aware of a function similar to "nargin" in Visual Basic. It could also be something like "if the argument "bovengrens" is defined". Does anybody know how to approach this problem? Thanks in advance.

但是，我不知道在Visual Basic中类似于“nargin”的函数。它也可能是“如果论证”bovengrens“被定义”。有人知道如何解决这个问题吗？提前致谢。

P.S. I am aware that I can make the code 'work' by filling in a very large number for the bracket 'boundary' in the top bracket, but I do not consider this elegant coding.

附：我知道我可以通过填充顶部括号中的括号“边界”的非常大的数字来使代码“工作”，但我不认为这种优雅的编码。

2 个解决方案

#1

You can use VBA's IsMissing function to test for optional parameters. Here's an example:

您可以使用VBA的IsMissing函数来测试可选参数。这是一个例子：

Public Sub OptionalArg(arg1, Optional arg2)
Debug.Print arg1; IIf(IsMissing(arg2), "missing", arg2)
End Sub

Test it like this:

像这样测试：

Sub Test()
OptionalArg 1
OptionalArg 1, 2
End Sub

#2

Just test the arguments using the IsMissing function:

只需使用IsMissing函数测试参数：

If IsMissing(bovengrens) Then ...

#1