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Evaluate Equation

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Submitted on: 2/12/2015 4:39:00 PM
By: Lefteris Eleftheriades (from psc cd)  
Level: Intermediate
User Rating: By 5 Users
Compatibility: VB 5.0, VB 6.0
Views: 781
 
     Evaluate any Mathematical Equation like: Evaluate("(5+3)*2")
 
code:
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'**************************************
' Name: Evaluate Equation
' Description:Evaluate any Mathematical Equation
like: Evaluate("(5+3)*2")
' By: Lefteris Eleftheriades (from psc cd)
'**************************************

Function Evaluate(ByVal Equation As String)
 Dim i&, P%, Si&
 Equation = Replace(Replace(Equation, ",", "."), "--", "")
 'Parenthesis Begins with outermost
 For i = 1 To Len(Equation)
If Mid(Equation, i, 1) = "(" Then
P = P + 1
If P = 1 Then Si = i
End If
If Mid(Equation, i, 1) = ")" Then
If P = 1 Then
 Evaluate = Evaluate(Mid(Equation, 1, Si - 1) & Evaluate(Mid(Equation, Si + 1, i - 1 - Si)) & Mid(Equation, i + 1))
 Exit Function
End If
P = P - 1
End If
 Next
 
 'Addition / Substruction
For i = Len(Equation) To 1 Step -1
 If Mid(Equation, i, 1) = "+" Then
If i > 1 Then
If Mid(Equation, i - 1, 1) <> "*" And Mid(Equation, i - 1, 1) <> "/" Then
 Evaluate = Evaluate(Mid(Equation, 1, i - 1)) + Evaluate(Mid(Equation, i + 1))
 Exit Function
End If
Else
Evaluate = Evaluate(Mid(Equation, 1, i - 1)) + Evaluate(Mid(Equation, i + 1))
Exit Function
End If
 End If
 If Mid(Equation, i, 1) = "-" Then
If i > 1 Then
If Mid(Equation, i - 1, 1) <> "*" And Mid(Equation, i - 1, 1) <> "/" Then
 Evaluate = Evaluate(Mid(Equation, 1, i - 1)) - Evaluate(Mid(Equation, i + 1))
 Exit Function
End If
Else
Evaluate = Evaluate(Mid(Equation, 1, i - 1)) - Evaluate(Mid(Equation, i + 1))
Exit Function
End If
 End If
Next
 
 'Multiplication / Division
 For i = Len(Equation) To 1 Step -1
If Mid(Equation, i, 1) = "*" Then
Evaluate = Evaluate(Mid(Equation, 1, i - 1)) * Evaluate(Mid(Equation, i + 1))
Exit Function
End If
If Mid(Equation, i, 1) = "/" Then
Evaluate = Evaluate(Mid(Equation, 1, i - 1)) / Evaluate(Mid(Equation, i + 1))
Exit Function
End If
 Next
 
 Evaluate = Val(Equation)
End Function


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