How can I get result from string formula as integer - vb.net

Question

How I can get result value from this string formula :
Dim Formula As String
Formula = "((5000 / 30) * (22 + 6)) + ((5000 / 30 / 8) * (20))"
Dim Result As Integer
Result = ?????
How can I get an integer result value? It's 5083.33

Answer 1

A bit simpler - use the .Compute method of the DataTable
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim dt As New DataTable
Dim r = dt.Compute("((5000 / 30) * (22 + 6)) + ((5000 / 30 / 8) * (20))", Nothing)
Debug.Print(r.ToString)
End Sub
Result in Immediate Window
5083.33333333333

Answer 2

Thanks every body,
I got the CODE right now as following :-
Just you Can Do ..... >>> NumericBox1 = EvaluateExpr(TextBox2.Text)
Private Function IsEmptyStack(ByVal AStack As Stack) As Boolean
Return (AStack.Count = 0)
End Function
Private Function IsOperator(ByVal AChar As Char) As Boolean
Return "^*/+-".Contains(AChar)
End Function
Private Function CompareOperators(ByVal Op1 As Char, ByVal Op2 As Char) As Integer
If Not (IsOperator(Op1) And IsOperator(Op2)) Then
Err.Raise(vbObjectError + 1001, "CompareOperators", "Operator(s) not suppoerted")
End If
Select Case Op1
Case "^"c
If Op2 = "^"c Then
Return 0
Else
Return 1
End If
Case "*"c, "/"c
Select Case Op2
Case "^"c
Return -1
Case "*"c, "/"c
Return 0
Case "+"c, "-"c
Return 1
End Select
Case "+"c, "-"c
Select Case Op2
Case "^"c, "*"c, "/"c
Return -1
Case "+"c, "-"c
Return 0
End Select
End Select
End Function
Private Function InfixToPostfix(ByVal InfixExpression As String) As String
Dim Infix As String
Dim Postfix As String
Dim InfixIndex As Integer
Dim InfixLen As Integer
Dim AChar As Char
Dim APeek As String
Dim ANumber As String
Dim MathStack As New Stack
Infix = InfixExpression.Trim()
If Infix = "" Then
Return ""
End If
Infix = Infix & ")"
ANumber = ""
Postfix = ""
InfixLen = Len(Infix) '- 1
InfixIndex = 0
MathStack.Clear()
MathStack.Push("(")
Do While (Not IsEmptyStack(MathStack)) And (InfixIndex <= InfixLen)
'AChar = Mid$(Infix, InfixIndex, 1)
AChar = Infix(InfixIndex)
If Char.IsDigit(AChar) Then
ANumber = ANumber & AChar
ElseIf AChar = "(" Then
If ANumber <> "" Then
Postfix = Postfix & ANumber & " "
ANumber = ""
End If
MathStack.Push(AChar)
ElseIf IsOperator(AChar) Then
If ANumber <> "" Then
Postfix = Postfix & ANumber & " "
ANumber = ""
End If
APeek = MathStack.Peek
If IsOperator(APeek) Then
Do While CompareOperators(APeek, AChar) >= 0
APeek = MathStack.Pop
Postfix = Postfix & APeek
APeek = MathStack.Peek
If Not IsOperator(APeek) Then Exit Do
Loop
End If
MathStack.Push(AChar)
ElseIf AChar = ")" Then
If ANumber <> "" Then
Postfix = Postfix & ANumber & " "
ANumber = ""
End If
APeek = MathStack.Peek
Do While APeek <> "("
APeek = MathStack.Pop
Postfix = Postfix & APeek
APeek = MathStack.Peek
Loop
MathStack.Pop()
End If
InfixIndex = InfixIndex + 1
Loop
If Not IsEmptyStack(MathStack) Then
Err.Raise(vbObjectError + 1002, "InfixToPostfix", "Invalid infix expression")
Else
InfixToPostfix = Postfix
End If
End Function
Private Function PerformOperation(ByVal Number1 As Double, ByVal Number2 As Double, ByVal AOperator As Char) As Double
Select Case AOperator
Case "+"c
Return Number1 + Number2
Case "-"c
Return Number1 - Number2
Case "*"c
Return Number1 * Number2
Case "/"c
If Number2 = 0 Then
Err.Raise(vbObjectError + 1004, "EvaluatePostfix", "Division by zero")
Else
Return Number1 / Number2
End If
Case "^"c
Return Number1 ^ Number2
Case Else
Err.Raise(vbObjectError + 1001, "CompareOperators", "Operator not suppoerted")
End Select
End Function
Private Function EvaluatePostfix(ByVal PostfixExpression As String) As Double
Dim Postfix As String
Dim ANumber As String
Dim AChar As Char
Dim PostfixIndex As Long
Dim PostfixLen As Long
Dim Num1 As Double
Dim Num2 As Double
Dim NumResult As Double
Dim MathStack As New Stack
Postfix = Trim$(PostfixExpression)
If Postfix = "" Then
Return 0.0
End If
Postfix = Postfix & "="
ANumber = ""
PostfixLen = Len(Postfix)
PostfixIndex = 0
MathStack.Clear()
Do While PostfixIndex <= PostfixLen
AChar = Postfix(PostfixIndex)
If AChar = " " Then
If ANumber <> "" Then
MathStack.Push(CDbl(ANumber))
ANumber = ""
End If
ElseIf Char.IsDigit(AChar) Then
ANumber = ANumber & AChar
ElseIf AChar = "=" Then
If ANumber <> "" Then
MathStack.Push(CDbl(ANumber))
ANumber = ""
End If
If MathStack.Count = 1 Then
Return MathStack.Pop
Else
Err.Raise(vbObjectError + 1003, "EvaluatePostfix", "Invalid postfix expression")
End If
ElseIf IsOperator(AChar) Then
If ANumber <> "" Then
MathStack.Push(CDbl(ANumber))
ANumber = ""
End If
If IsEmptyStack(MathStack) Then
Err.Raise(vbObjectError + 1003, "EvaluatePostfix", "Invalid postfix expression")
Else
Num2 = MathStack.Pop
If IsEmptyStack(MathStack) Then
Err.Raise(vbObjectError + 1003, "EvaluatePostfix", "Invalid postfix expression")
Else
Num1 = MathStack.Pop
NumResult = PerformOperation(Num1, Num2, AChar)
MathStack.Push(NumResult)
End If
End If
End If
PostfixIndex = PostfixIndex + 1
Loop
End Function
Public Function EvaluateExpr(ByVal AExpr As String) As String
Dim PostfixExpr As String
AExpr = AExpr.Trim
If AExpr = "" Then Return ""
PostfixExpr = InfixToPostfix(AExpr)
Return EvaluatePostfix(PostfixExpr)
End Function

Answer 3

This shouldn't really qualify as an answer, but I thought it would be fun to re-write that big code block using more modern techniques. I've done this right in the reply window, so there are probably several errors. It's worth noting, though, how much shorter this is.
We could have even more fun, and probably perform better, by also re-writing the code to think in terms of breaking apart the string into tokens, rather than by character.
Public Module Math
'Reverse precedence order, so higher precedence has higher index
Private operators As String = "-+/*^"
Private Function CompareOperators(Op1 As Char, Op2 As Char) As Integer
Dim Op1Value As Integer = operators.IndexOf(Op1)
Dim Op2Value As Integer = operators.IndexOf(Op2)
If Op1Value = -1 Then Throw New Exception($"Unsupported operator {Op1} detected")
If Op2Value = -1 Then Throw New Excpetion($"Unsupported operator {Op2} detected")
'The \ 2 adjusts for same precedence of +- and */
Return (Op1Value \ 2).CompareTo(Op2Value \ 2)
End Function
Private Function InfixToPostfix(InfixExpression As String) As String
If String.IsNullOrWhitesapce(InfixExpression) Then Return ""
InfixExpression = InfixExpression.Trim() & ")"
Dim result As New StringBuilder()
Dim MathStack As New Stack(Of Char)()
Dim ANumber As String = ""
Dim Index As Integer = 0
MathStack.Push("("c)
While MathStack.Count > 0 AndAlso Index <= InfixExpression.Length)
Dim AChar As Char = InfixExpression(Index)
If Char.IsDigit(AChar) Then
ANumber &= ANumber & AChar
ElseIf AChar = "("c Then
If Not String.IsNullOrEmpty(ANumber) Then
result.Append(ANumber).Append(" ")
ANumber = ""
End If
MathStack.Push(AChar)
ElseIf IsOperator(AChar) Then
If Not String.IsNullOrEmpty(ANumber) Then
result.Append(ANumber).Append(" ")
ANumber = ""
End If
Dim APeek As Char = MathStack.Peek()
If IsOperator(APeek) Then
While CompareOperators(APeek, AChar) >= 0
APeek = MathStack.Pop()
result.Append(APeek)
APeek = MathStack.Peek
If Not IsOperator(APeek) Then Exit While
End While
End If
MathStack.Push(AChar)
ElseIf AChar = ")"c Then
If Not String.IsNullOrEmpty(ANumber) Then
result.Append(ANumber).Append(" ")
ANumber = ""
End If
APeek = MathStack.Peek()
While APeek <> "("c
APeek = MathStack.Pop()
result.Append(APeek)
APeek = MathStack.Peek()
End While
MathStack.Pop()
End If
Index += 1
End While
If MathStack.Count > 0 Then
Throw New Exception("Invalid infix expression: stack is not empty")
End If
Return result.ToString()
End Function
Private Function PerformOperation(Number1 As Double, Number2 As Double, AOperator As Char) As Double
Select Case AOperator
Case "+"c
Return Number1 + Number2
Case "-"c
Return Number1 - Number2
Case "*"c
Return Number1 * Number2
Case "/"c
'We could detect Number2 = 0 here, but appropriate response is throwing the same DivideByZeroException the framework will do for us anyway
Return Number1 / Number2
Case "^"c
Return Number1 ^ Number2
Case Else
Throw New Exception($"Operator {AOperator} not supported")
End Select
End Function
Private Function EvaluatePostfix(Expression As String) As Double
Dim result As Double = 0R
If String.IsNullOrWhitespace(Expression) Then Return result
Expression = Expression.Trim() & "="
Dim MathStack As New Stack(Of Double)()
Dim ANumber As String = ""
Dim Index As Integer = 0
Do While Index <= Expression.Length
AChar = Expression(Index)
If AChar = " "c Then
If Not String.IsNullOrEmpty(ANumber) Then
MathStack.Push(CDbl(ANumber))
ANumber = ""
End If
ElseIf Char.IsDigit(AChar) Then
ANumber = ANumber & AChar
ElseIf AChar = "="c Then
If Not String.IsNullOrEmpty(ANumber) Then
MathStack.Push(CDbl(ANumber))
ANumber = ""
End If
If MathStack.Count = 1 Then Return MathStack.Pop()
Throw New Exception("Invalid postfix expression")
ElseIf IsOperator(AChar) Then
If Not String.IsNullOrEmpty(ANumber) Then
MathStack.Push(CDbl(ANumber))
ANumber = ""
End If
If MathStack.Count < 2 Then
Throw New Exception("Invalid postfix expression: insufficient stack")
End If
Dim Num2 As Double = MathStack.Pop()
MathStack.Push(PerformOperation(MathStack.Pop(), Num2))
End If
Index += 1
Loop
End Function
Public Function EvaluateExpr(AExpr As String) As String
If String.IsNullOrWhitespacE(AExpr) Then Return ""
Return EvaluatePostfix(InfixToPostfix(AExpr))
End Function
End Module
Wanted to do the token option for more fun:
Public Module Math
'Reverse precedence order, so higher precedence has higher index
Private operators As String = "()-+/*^"
Private Function IsOperator(AChar As Char) As Boolean
Return operators.Contains(AChar)
End Function
Private Function CompareOperators(Op1 As Char, Op2 As Char) As Integer
Dim Op1Value As Integer = operators.IndexOf(Op1)
Dim Op2Value As Integer = operators.IndexOf(Op2)
If Op1Value = -1 Then Throw New Exception($"Unsupported operator '{Op1}' detected")
If Op2Value = -1 Then Throw New Exception($"Unsupported operator '{Op2}' detected")
'The \ 2 adjusts for same precedence of +- and */
Return (Op1Value \ 2).CompareTo(Op2Value \ 2)
End Function
Private Iterator Function Tokenize(input As String) As IEnumerable(Of String)
Dim buffer As String = ""
For Each c As Char In input
If Char.IsWhitespace(c) Then
If String.IsNullOrEmpty(buffer) Then Continue For
Yield buffer
buffer = ""
ElseIf Char.IsDigit(c) OrElse c = "."c Then
buffer &= c 'Don't worry about validating good numbers at this level. Just check the characters
ElseIf c = "-"c Then ' could be operator or negative sign
If buffer.Length > 0 Then 'was an operator
Yield buffer
buffer = ""
Yield c.ToString()
Else 'Not sure yet -- treat as digit for now
buffer &= c
End If
ElseIf operators.Contains(c) OrElse "()".Contains(c) Then
If buffer.Length > 0 Then
Yield buffer
buffer = ""
End If
Yield c.ToString()
Else
Throw New Exception($"Unexpected character '{c}' in input")
End If
Next c
If buffer.Length > 0 Then Yield buffer
End Function
Private Iterator Function InfixToPostfix(tokens As IEnumerable(Of String)) As IEnumerable(Of String)
Dim buffer As New Stack(Of String)()
Dim temp As Double
For Each token As String In tokens
If Double.TryParse(token, temp) Then
Yield token
'Need to account for "(" better
ElseIf token = "(" Then
buffer.Push(token)
ElseIf operators.Contains(token) AndAlso token <> ")" Then
If buffer.Count = 0 Then
buffer.Push(token)
ElseIf CompareOperators(token, buffer.Peek()) > 0 Then
buffer.Push(token)
Else
While CompareOperators(token, buffer.Peek()) <= 0
Dim tok As String = buffer.Pop()
If Not "()".Contains(tok) Then Yield tok
If buffer.Count = 0 Then Exit While
End While
buffer.Push(token)
End If
ElseIf token = ")" Then
Dim valid As Boolean = False
While buffer.Count > 0
Dim tok As String = buffer.Pop()
If tok = "(" Then
valid = True
Exit While
Else
Yield tok
End If
End While
If Not valid Then Throw New Exception("Unbalanced parentheses in expression (missing matching '(' character)")
Else
Throw New Exception($"Unknown token type '{token}'")
End If
Next token
While buffer.Count > 0
Dim tok As String = buffer.Pop()
If Not "()".Contains(tok) Then Yield tok
End While
End Function
Private Function PerformOperation(Number1 As Double, Number2 As Double, AOperator As Char) As Double
Select Case AOperator
Case "+"c
Return Number1 + Number2
Case "-"c
Return Number1 - Number2
Case "*"c
Return Number1 * Number2
Case "/"c
'We could detect Number2 = 0 here, but appropriate response is throwing the same DivideByZeroException the framework will do for us anyway
Return Number1 / Number2
Case "^"c
Return Number1 ^ Number2
Case Else
Throw New Exception($"Operator {AOperator} not supported")
End Select
End Function
Private Function EvaluatePostfix(tokens As IEnumerable(Of String)) As Double
Dim result As Double = 0R
Dim buffer As New Stack(Of Double)()
Dim temp As Double
For Each token As String In tokens
If Double.TryParse(token, temp) Then
buffer.Push(temp)
ElseIf buffer.Count < 2 Then
Throw New Exception("Invalid postfix expression")
Else
temp = buffer.Pop()
temp = PerformOperation(buffer.Pop(), temp, token(0))
buffer.Push(temp)
End If
Next token
If buffer.Count > 1 Then Throw New Exception("Invalid expression: extra items in the buffer")
If buffer.Count = 0 Then Throw New Exception("Invalid expression: no result")
Return buffer.Pop()
End Function
Public Function Evaluate(input As String) As Double
If String.IsNullOrWhiteSpace(input) Then Return 0R
Dim tokens = Tokenize(input)
tokens = InfixToPostfix(tokens)
Return EvaluatePostfix(tokens)
End Function
End Module