Question

VB编程中必选参数什么意思

有个求pi的近似值的程序，要求用VB过程编写，我写的为何出现编译错误：缺少:)和必选参数错误.
程序如下：Sub sum(n As Integer)
n = InputBox("输入n值")
Dim i As Integer
sum = 0
For i = 1 To n

sum = sum + (-1)^(i-1)*(1/(2i-1))
Next i
Print "4*sum="; 4 * sum

End Sub
Private Sub Command1_Click()
Dim a As Integer
a = InputBox("输入a值")
sum a

End Sub

望各位大哥帮帮忙。谢了。

Answer 1

提示必选参数的原因是
sum = 0
这一句，VB当作你是调用sum(n As Integer) 这个方法了，可以将sum=0这句换成其他变量。或者将该方法声明为函数
Private Function sum(n As Integer) as double

此时使用 sum = 0表示将函数返回值设为0

Answer 2

你那个sub应该改为function，另有一句多余的，其它对照一下改就可以了：
Private Function sum(n As Integer)
Dim i As Integer
sum = 0
For i = 1 To n

sum = sum + (-1) ^ (i - 1) * (1 / (2 * i - 1))
Next i
Print "4*sum="; 4 * sum

End Function
Private Sub Command1_Click()
Dim a As Integer
a = InputBox("输入a值")
sum a

End Sub

Answer 3

程序如下：
Function sum(n As Integer)
n = InputBox("输入n值")
Dim i As Integer
sum = 0
For i = 1 To n
sum = sum + (-1)^(i-1)*(1/(2i-1))
Next i
Print "4*sum="; 4 * sum
End Sub

Private Sub Command1_Click()
Dim a As Integer,b As Double
a = InputBox("输入a值")
b=sum(a)
End Sub