学进去

小龙同学设计了一个求四则混合运算结果的程序，用于计算不带括号的+、-、*、\的运算， \为整除运算，且此处要求*和\的优先级相同。在表达式中输入待求解的表达式，以=结尾。按下 Command1“计算”按钮后，在标签控件 Label1 中输出运算结果。程序界面如下图所示：

（1）在表达式中输入15-22\5*2+7=，则输出的结果是    。
（2）实现上述功能的 VB 程序如下，请在划线处填入合适代码。
Function calculate(x As Integer, y As Integer, op As String) As Integer If op = "+" Then calculate = x + y
If op = "-" Then calculate = x - y If op = "*" Then calculate = x * y If op = "\" Then calculate = x \ y
End Function
Function state(op As String) As Integer If op = "#" Then state = -1
If op = "=" Then state = 1
If op = "+" Then state = 1
If op = "-" Then state = 1
     '① 
If op = "*" Then state = 3
End Function
Private Sub Command1_Click()
Dim s As String, length As Integer, t As String Dim k As Integer, q As Integer
Dim opt(0 To 3) As String Dim i As Integer
Dim s1 As String
Dim a(1 To 3) As Integer s = Text1.Text
length = Len(s)
t = "": k = 0: q = 0: opt(q) = "#"
For i = 1 To length s1 = Mid(s, i, 1)
If s1 >= "0" And s1 <= "9" Then
t = t + s1

Else

k = k + 1 a(k) = Val(t) t = ""
Do While    '②
a(k - 1) = calculate(a(k - 1), a(k), opt(q))
k = k - 1
q= q - 1
Loop
q = q + 1
      '③

If s1 = "=" Then Label1.Caption = Str(a(1))

End If

Next i

End Sub