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'再发一个,非原创,作者不详,不到50行的单函数实现四则运算表达式计算求值.
'standard project
'all in module
Option Explicit
Private Function Eval(ByVal s As String) As Variant
Dim Lb As Long, Rb As Long
Lb = InStrRev(s, "(")
While Lb <> 0
Rb = InStr(Lb, s, ")")
s = Replace(s, Mid$(s, Lb, Rb - Lb + 1), CStr(Eval(Mid$(s, Lb + 1, Rb - Lb - 1))))
Lb = InStrRev(s, "(")
Wend
If IsNumeric(s) Then
Eval = Val(s)
Else
Dim High As Long
High = InStr(s, "+")
If High <> 0 Then
Eval = Eval(Left$(s, High - 1)) + Eval(Right$(s, Len(s) - High))
Exit Function
End If
High = InStrRev(s, "-")
If High <> 0 Then
Eval = Eval(Left$(s, High - 1)) - Eval(Right$(s, Len(s) - High))
Exit Function
End If
High = InStr(s, "*")
If High <> 0 Then
Eval = Eval(Left$(s, High - 1)) * Eval(Right$(s, Len(s) - High))
Exit Function
End If
High = InStrRev(s, "/")
If High <> 0 Then
Eval = Eval(Left$(s, High - 1)) / Eval(Right$(s, Len(s) - High))
Exit Function
End If
High = InStrRev(s, "%")
If High <> 0 Then
Eval = Eval(Left$(s, High - 1)) Mod Eval(Right$(s, Len(s) - High))
Exit Function
End If
High = InStrRev(s, "!=")
If High <> 0 Then
Eval = Eval(Left$(s, High - 1)) <> Eval(Right$(s, Len(s) - High - 1))
Exit Function
End If
High = InStrRev(s, "==")
If High <> 0 Then
Eval = (Eval(Left$(s, High - 1)) = Eval(Right$(s, Len(s) - High - 1)))
Exit Function
End If
End If
End Function
'主函数
Public Sub main()
Dim Expression As String
Expression = "149.5+((100+(6+(90-5*2*2)*4+(1-1))+202)%441)*2*2+0.88+150.5"
MsgBox Eval(Expression)
End Sub
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