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2008年12月30日星期二

VB表达式计算函数(修正1)

有问题请联系我。
感谢Aegisys[0GiNr]发现未检查减法运算的错误
感谢iceboy发现小数识别的错误


'函数:Calc(Exp As String) As Double
'用于计算包含括号、四则运算的字符串表达式

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'叠代深度(调试用)
'Public Deep As Integer

Public CalcErr As String

Public Function Calc(ByVal Exp As String) As Double
CalcErr = ""
'去空格
Exp = Replace(Exp, " ", "")
'去掉最外括号
While Left(Exp, 1) = "(" And Right(Exp, 1) = ")"
Exp = Mid(Exp, 2, Len(Exp) - 2)
Wend
'括号配对检查
Dim I As Integer, CountL As Integer, CountR As Integer, Chr As String
For I = 1 To Len(Exp)
Chr = Mid(Exp, I, 1)
If Chr = "(" Then
CountL = CountL + 1
ElseIf Chr = ")" Then
CountR = CountR + 1
End If
Next
If CountL <> CountR Then
CalcErr = "括号不匹配"
Exit Function
End If
'计算
Calc = CalcA(Exp)
End Function

Public Function CalcA(ByVal Exp As String) As Double
'Deep = Deep + 1
'(1+2)*3+4*5+2=?
'(1+2)*(3+4)+5=?
'(1+2)*((3+4)*5)+3=?
'11111012222211100

DoEvents '防止死机
Dim LvS As Integer

'循环变量
Dim I As Integer, J As Integer

'对于纯数值
Dim Temp As String, Temp2 As String
Temp = Str(Val(Exp))
Temp2 = Replace(Temp, ".", "0.")
Exp = Trim(Exp)
If Trim(Temp) = Exp Or Trim(Temp2) = Exp Then
CalcA = Val(Exp)
GoTo LAB_END
ElseIf Exp = "" Then '对于空(负号)
CalcA = 0
GoTo LAB_END
End If

'Dim AscN As Integer
'For I = 1 To Len(Exp)
' AscN = Asc(Mid(Exp, I, 1))
' If AscN > 57 Or AscN < ascn =" 47" ascn =" 44" calca =" Val(Exp)" i =" 1" lvs =" I" currentlv =" 0:" lvmb =" False" i =" LvS" currentlv =" CurrentLv"> LvM Then
LvM = CurrentLv
LvMS = I '最大级别启始点
LvMB = True
End If
ElseIf Mid(Exp, I, 1) = ")" Then
CurrentLv = CurrentLv - 1
If LvMB Then
LvME = I '最大级别结束点
LvMB = False
End If
End If
'Lv(I) = CurrentLv '存储级别(优化备用)
Next
'计算最高级括号
Exp = Left(Exp, LvMS - 1) & CalcA(Mid(Exp, LvMS + 1, LvME - LvMS - 1)) & Right(Exp, Len(Exp) - LvME)
CalcA = CalcA(Exp)
GoTo LAB_END

LAB_A2:
'对于没有括号的表达式
'加减法跳转
Dim AscS As Integer
For I = 1 To Len(Exp)
If Mid(Exp, I, 1) = "+" Then GoTo LAB_B1
If Mid(Exp, I, 1) = "-" And I > 1 Then
AscS = Asc(Mid(Exp, I - 1, 1))
If AscS >= Asc("0") And AscS < i =" 1" exp =" CalcA(Left(Exp," calca =" CalcA(Exp)" exp =" Str(CalcA(Left(Exp," calca =" CalcA(Exp)" i =" 1" exp =" Str(CalcA(Left(Exp," calca =" CalcA(Exp)" exp =" Str(CalcA(Left(Exp," calca =" CalcA(Exp)" deep =" Deep">

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