Public Function CalculateString(ByVal Exppression As String, ByRef Good As Boolean, ByVal xxx As Double) As Double

Dim isg As Boolean

Dim ExppressionLength As Long

Dim pp As Integer

pp = 1

ExppressionLength = Len(Exppression)

CalculateString = E(Exppression, isg, pp, xxx)

Good = isg

If pp <= ExppressionLength Then Good = False

End Function

Private Function E(ByVal Exppression As String, ByRef Good As Boolean, ByRef position As Integer, ByVal xxx As Double) As Double

Dim tmp1, tmp2 As Double

Dim isg As Boolean

On Error GoTo Eerr

tmp1 = T(Exppression, isg, position, xxx)

If Match(Exppression, "+", position) Then

position = position + 1

tmp2 = E2(Exppression, isg, position, xxx)

If Not (isg) Then

Good = False

Exit Function

End If

E = tmp1 + tmp2

Else

If Match(Exppression, "-", position) Then

position = position + 1

tmp2 = E2(Exppression, isg, position, xxx)

If Not (isg) Then

Good = False

Exit Function

End If

E = tmp1 - tmp2

Else

E = tmp1

End If

End If

Good = isg

Exit Function

Eerr:

Good = False

End Function

Private Function E2(ByVal Exppression As String, ByRef Good As Boolean, ByRef position As Integer, ByVal xxx As Double) As Double

Dim tmp1, tmp2 As Double

Dim isg As Boolean

tmp1 = T2(Exppression, isg, position, xxx)

If Match(Exppression, "+", position) Then

position = position + 1

tmp2 = E2(Exppression, isg, position, xxx)

If Not (isg) Then

Good = False

Exit Function

End If

E2 = tmp1 + tmp2

Else

If Match(Exppression, "-", position) Then

position = position + 1

tmp2 = E2(Exppression, isg, position, xxx)

If Not (isg) Then

Good = False

Exit Function

End If

E2 = tmp1 - tmp2

Else

E2 = tmp1

End If

Good = isg

End If

End Function

Private Function T(ByVal Exppression As String, ByRef Good As Boolean, ByRef position As Integer, ByVal xxx As Double) As Double

Dim tmp1, tmp2 As Double

Dim isg As Boolean

tmp1 = F(Exppression, isg, position, xxx)

If isg Then

If Match(Exppression, "*", position) Then

position = position + 1

tmp2 = T2(Exppression, isg, position, xxx)

If Not (isg) Then

Good = False

Exit Function

End If

T = tmp1 * tmp2

Else

If Match(Exppression, "/", position) Then

position = position + 1

tmp2 = T2(Exppression, isg, position, xxx)

If Not (isg) Then

Good = False

Exit Function

End If

T = tmp1 / tmp2

Else

T = tmp1

End If

End If

End If

Good = isg

End Function

Private Function T2(ByVal Exppression As String, ByRef Good As Boolean, ByRef position As Integer, ByVal xxx As Double) As Double

Dim tmp1, tmp2 As Double

Dim isg As Boolean

tmp1 = F2(Exppression, isg, position, xxx)

If isg Then

If Match(Exppression, "*", position) Then

position = position + 1

tmp2 = T2(Exppression, isg, position, xxx)

If Not (isg) Then

Good = isg

Exit Function

End If

T2 = tmp1 * tmp2

Else

If Match(Exppression, "/", position) Then

position = position + 1

tmp2 = T2(Exppression, isg, position, xxx)

If Not (isg) Then

Good = isg

Exit Function

End If

T2 = tmp1 / tmp2

Else

T2 = tmp1

End If

End If

End If

Good = isg

End Function

Private Function F(ByVal Exppression As String, ByRef Good As Boolean, ByRef position As Integer, ByVal xxx As Double) As Double

Dim tmp As Double

Dim isg As Boolean

tmp = OpDigital(Exppression, isg, position, xxx)

If Not (isg) Then tmp = G(Exppression, isg, position, xxx)

F = tmp

Good = isg

End Function

Private Function F2(ByVal Exppression As String, ByRef Good As Boolean, ByRef position As Integer, ByVal xxx As Double) As Double

Dim tmp As Double

Dim isg As Boolean

tmp = NonopDigital(Exppression, isg, position, xxx)

If Not (isg) Then tmp = G(Exppression, isg, position, xxx)

F2 = tmp

Good = isg

End Function

Private Function G(ByVal Exppression As String, ByRef Good As Boolean, ByRef position As Integer, ByVal xxx As Double) As Double

Dim tmp1, tmp2 As Double

Dim isg As Boolean

Call PassBlank(Exppression, position)

If Match(Exppression, "SIN", position) Then

position = position + 3

Call PassBlank(Exppression, position)

G = Sin(G2(Exppression, Good, position, xxx))

Call PassBlank(Exppression, position)

Exit Function

End If

If Match(Exppression, "COS", position) Then

position = position + 3

Call PassBlank(Exppression, position)

G = Cos(G2(Exppression, Good, position, xxx))

Call PassBlank(Exppression, position)

Exit Function

End If

If Match(Exppression, "TAN", position) Then

position = position + 3

Call PassBlank(Exppression, position)

G = Tan(G2(Exppression, Good, position, xxx))

Call PassBlank(Exppression, position)

Exit Function

End If

If Match(Exppression, "LOG", position) Then

position = position + 3

Call PassBlank(Exppression, position)

G = Log(G2(Exppression, Good, position, xxx)) / Log(10#)

Call PassBlank(Exppression, position)

Exit Function

End If

If Match(Exppression, "LN", position) Then

position = position + 2

Call PassBlank(Exppression, position)

G = Log(G2(Exppression, Good, position, xxx))

Call PassBlank(Exppression, position)

Exit Function

End If

If Match(Exppression, "EXP", position) Then

position = position + 3

Call PassBlank(Exppression, position)

G = Exp(G2(Exppression, Good, position, xxx))

Call PassBlank(Exppression, position)

Exit Function

End If

If Match(Exppression, "ARCTAN", position) Then

position = position + 6

Call PassBlank(Exppression, position)

G = Atn(G2(Exppression, Good, position, xxx))

Call PassBlank(Exppression, position)

Exit Function

End If

If Match(Exppression, "ARCSIN", position) Then

position = position + 6

Call PassBlank(Exppression, position)

tmp1 = G2(Exppression, Good, position, xxx)

If tmp1 <> 1 And tmp1 <> -1 Then

G = Atn(tmp1 / Sqr(1 - tmp1 * tmp1))

Else

If tmp1 = 1 Then G = Pi / 2 Else G = -Pi / 2

End If

Call PassBlank(Exppression, position)

Exit Function

End If

If Match(Exppression, "ARCCOS", position) Then

position = position + 6

Call PassBlank(Exppression, position)

tmp1 = G2(Exppression, Good, position, xxx)

If tmp1 <> 1 And tmp1 <> -1 Then

G = Atn(-tmp1 / Sqr(1 - tmp1 * tmp1)) + Pi / 2

Else

If tmp1 = 1 Then G = 0# Else G = Pi

End If

Call PassBlank(Exppression, position)

Exit Function

End If

If Match(Exppression, "POW", position) Then

position = position + 3

Call PassBlank(Exppression, position)

If Match(Exppression, "(", position) Then

position = position + 1

tmp1 = E(Exppression, isg, position, xxx)

If Match(Exppression, ",", position) And isg Then

position = position + 1

tmp2 = E(Exppression, isg, position, xxx)

If Match(Exppression, ")", position) And isg Then

position = position + 1

Call PassBlank(Exppression, position)

Good = True

G = tmp1 ^ tmp2

Exit Function

End If

End If

End If

Good = False

Exit Function

End If

G = G2(Exppression, Good, position, xxx)

Call PassBlank(Exppression, position)

End Function

Private Function G2(ByVal Exppression As String, ByRef Good As Boolean, ByRef position As Integer, ByVal xxx As Double) As Double

Dim tmp As Double

Dim isg As Boolean

If Match(Exppression, "(", position) Then

position = position + 1

Call PassBlank(Exppression, position)

tmp = E(Exppression, isg, position, xxx)

If isg And Match(Exppression, ")", position) Then

G2 = tmp

position = position + 1

Good = True

Else

Good = False

End If

End If

End Function

Private Function NonopDigital(ByVal Exppression As String, ByRef Good As Boolean, ByRef position As Integer, ByVal xxx As Double) As Double

Dim tmp1, tmp2 As Double

Dim tmpStr As String

Call PassBlank(Exppression, position)

If Match(Exppression, "X", position) Then

NonopDigital = xxx

Good = True

position = position + 1

Call PassBlank(Exppression, position)

Exit Function

End If

tmp1 = 0

tmp2 = 0

tmpStr = Mid(Exppression, position, 1)

If tmpStr >= "0" And tmpStr <= "9" Then

While tmpStr >= "0" And tmpStr <= "9" Or tmpStr = " "

tmp2 = tmp2 + 1

tmpStr = Mid(Exppression, position + tmp2, 1)

Wend

If tmpStr = "." Then tmp2 = tmp2 + 1

tmpStr = Mid(Exppression, position + tmp2, 1)

While tmpStr >= "0" And tmpStr <= "9" Or tmpStr = " "

tmp2 = tmp2 + 1

tmpStr = Mid(Exppression, position + tmp2, 1)

Wend

If tmpStr = "E" Then tmp2 = tmp2 + 1

tmpStr = Mid(Exppression, position + tmp2, 1)

While tmpStr >= "0" And tmpStr <= "9" Or tmpStr = " "

tmp2 = tmp2 + 1

tmpStr = Mid(Exppression, position + tmp2, 1)

Wend

tmp1 = Val(Mid(Exppression, position))

position = position + tmp2

Good = True

Else

Good = False

End If

NonopDigital = tmp1

End Function

Private Function OpDigital(ByVal Exppression As String, ByRef Good As Boolean, ByRef position As Integer, ByVal xxx As Double) As Double

Dim tmp As Double

Dim isg As Boolean

Dim sign As Integer

sign = 1

Call PassBlank(Exppression, position)

If Match(Exppression, "X", position) Then

OpDigital = xxx

Good = True

position = position + 1

Call PassBlank(Exppression, position)

Exit Function

End If

If Match(Exppression, "-", position) Then

position = position + 1

sign = -1

Else

If Match(Exppression, "+", position) Or Mid(Exppression, position, 1) >= "0" And Mid(Exppression, position, 1) <= "9" Then

sign = 1

Else

Good = False

Exit Function

End If

End If

tmp = F2(Exppression, isg, position, xxx)

If Not (isg) Then Good = False Else Good = True

OpDigital = tmp * sign

End Function

Private Function Match(ByVal Exppression As String, ByVal Exppression2 As String, ByRef position As Integer) As Boolean

If Mid(Exppression, position, Len(Exppression2)) = Exppression2 Then Match = True Else Match = False

End Function

Private Sub PassBlank(ByVal Exppression As String, ByRef position)

While Mid(Exppression, position, 1) = " "

position = position + 1

Wend

End Sub Private Sub Command1_Click() Dim strexp As String, temp As String Dim a As Double, b As Boolean Dim i As Integer strexp = Text1.Text For i = 1 To Len(strexp) temp = Mid(strexp, i, 1) If Asc(temp) <= Asc("z") And Asc(temp) >= Asc("a") Then strexp = Left(strexp, i - 1) + StrConv(temp, vbUpperCase) + Right(strexp, Len(strexp) - i) End If Next i a = CalculateString(strexp, b, 1) If b = True Then Label1.Caption = "计算结果为: " + Str$(a) Else Label1.Caption = "公式有错误" End If End Sub