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textbox input ( 5* 2 ) + (5 * (2 + 3)) - 2 + 3, should get answer 36

Posted on 2006-06-13
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textbox input ( 5* 2 ) + (5 * (2 + 3)) - 2 + 3, should get answer 36.

how to do it

Jini
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Question by:Jini Jose
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by:Guy Hengel [angelIII / a3]
ID: 16892445
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by:Jini Jose
ID: 16892452
no not through script control
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by:Guy Hengel [angelIII / a3]
ID: 16892478
why not? does the job!
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by:Jini Jose
ID: 16892493
not possible
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by:Guy Hengel [angelIII / a3]
ID: 16892504
WHY not possible?
WHY reinvent the wheel?
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by:Jini Jose
ID: 16892515
no time to do
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by:Jini Jose
ID: 16892534
i want the vb function code
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by:Guy Hengel [angelIII / a3]
ID: 16892790
>no time to do

well, using the vb script control is done in 10 seconds, just check the reference in the project references, put a script control on the form, and use it's eval function.
there will be no faster than that...
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by:rockiroads
ID: 16893045
Would doing

Eval(txtBox.Value)

bring it up?

txtBox holds your maths  ( 5* 2 ) + (5 * (2 + 3)) - 2 + 3

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Accepted Solution

by:
wraith821 earned 250 total points
ID: 16893258
Here you go. i use it in an  sales commision calculator i built.


'***************** USAGE *************
Msgbox EvaluateExpression(txtBox.text)
'*************************************

'************* MODULE CODE *****************
' Evaluate the expression.
Public Function EvaluateExpression(ByVal expression As String) As Double
Const PREC_NONE = 11
Const PREC_UNARY = 10   ' Not actually used.
Const PREC_POWER = 9
Const PREC_TIMES = 8
Const PREC_DIV = 7
Const PREC_INT_DIV = 6
Const PREC_MOD = 5
Const PREC_PLUS = 4

Dim expr As String
Dim is_unary As Boolean
Dim next_unary As Boolean
Dim parens As Integer
Dim pos As Integer
Dim expr_len As Integer
Dim ch As String
Dim lexpr As String
Dim rexpr As String
Dim Value As String
Dim status As Long
Dim best_pos As Integer
Dim best_prec As Integer

    ' Remove all spaces.
    expr = Replace$(expression, " ", "")
    expr_len = Len(expr)
    If expr_len = 0 Then
        EvaluateExpression = 0
        Exit Function
    End If

    ' If we find + or - now, it is a unary operator.
    is_unary = True

    ' So far we have nothing.
    best_prec = PREC_NONE

    ' Find the operator with the lowest precedence.
    ' Look for places where there are no open
    ' parentheses.
    For pos = 1 To expr_len
        ' Examine the next character.
        ch = Mid$(expr, pos, 1)

        ' Assume we will not find an operator. In
        ' that case, the next operator will not
        ' be unary.
        next_unary = False

        If ch = " " Then
            ' Just skip spaces. We keep them here
            ' to make the error messages easier to
        ElseIf ch = "(" Then
            ' Increase the open parentheses count.
            parens = parens + 1

            ' A + or - after "(" is unary.
            next_unary = True
        ElseIf ch = ")" Then
            ' Decrease the open parentheses count.
            parens = parens - 1

            ' An operator after ")" is not unary.
            next_unary = False

            ' If parens < 0, too many ')'s.
            If parens < 0 Then
                Err.Raise vbObjectError + 1001, _
                    "EvaluateExpression", _
                    "Too many )s in '" & _
                    expression & "'"
            End If
        ElseIf parens = 0 Then
            ' See if this is an operator.
            If ch = "^" Or ch = "*" Or _
               ch = "/" Or ch = "\" Or _
               ch = "%" Or ch = "+" Or _
               ch = "-" _
            Then
                ' An operator after an operator
                ' is unary.
                next_unary = True

                ' See if this operator has higher
                ' precedence than the current one.
                Select Case ch
                    Case "^"
                        If best_prec >= PREC_POWER Then
                            best_prec = PREC_POWER
                            best_pos = pos
                        End If

                    Case "*", "/"
                        If best_prec >= PREC_TIMES Then
                            best_prec = PREC_TIMES
                            best_pos = pos
                        End If

                    Case "\"
                        If best_prec >= PREC_INT_DIV Then
                            best_prec = PREC_INT_DIV
                            best_pos = pos
                        End If

                    Case "%"
                        If best_prec >= PREC_MOD Then
                            best_prec = PREC_MOD
                            best_pos = pos
                        End If

                    Case "+", "-"
                        ' Ignore unary operators
                        ' for now.
                        If (Not is_unary) And _
                            best_prec >= PREC_PLUS _
                        Then
                            best_prec = PREC_PLUS
                            best_pos = pos
                        End If
                End Select
            End If
        End If
        is_unary = next_unary
    Next pos

    ' If the parentheses count is not zero,
    ' there's a ')' missing.
    If parens <> 0 Then
        Err.Raise vbObjectError + 1002, _
            "EvaluateExpression", "Missing ) in '" & _
            expression & "'"
    End If
   
    ' Hopefully we have the operator.
    If best_prec < PREC_NONE Then
        lexpr = Left$(expr, best_pos - 1)
        rexpr = Mid$(expr, best_pos + 1)
        Select Case Mid$(expr, best_pos, 1)
            Case "^"
                EvaluateExpression = _
                    EvaluateExpression(lexpr) ^ _
                    EvaluateExpression(rexpr)
            Case "*"
                EvaluateExpression = _
                    EvaluateExpression(lexpr) * _
                    EvaluateExpression(rexpr)
            Case "/"
                EvaluateExpression = _
                    EvaluateExpression(lexpr) / _
                    EvaluateExpression(rexpr)
            Case "\"
                EvaluateExpression = _
                    EvaluateExpression(lexpr) \ _
                    EvaluateExpression(rexpr)
            Case "%"
                EvaluateExpression = _
                    EvaluateExpression(lexpr) Mod _
                    EvaluateExpression(rexpr)
            Case "+"
                EvaluateExpression = _
                    EvaluateExpression(lexpr) + _
                    EvaluateExpression(rexpr)
            Case "-"
                EvaluateExpression = _
                    EvaluateExpression(lexpr) - _
                    EvaluateExpression(rexpr)
        End Select
        Exit Function
    End If

    ' If we do not yet have an operator, there
    ' are several possibilities:
    '
    ' 1. expr is (expr2) for some expr2.
    ' 2. expr is -expr2 or +expr2 for some expr2.
    ' 3. expr is Fun(expr2) for a function Fun.
    ' 4. expr is a primitive.
    ' 5. It's a literal like "3.14159".

    ' Look for (expr2).
    If Left$(expr, 1) = "(" And Right$(expr, 1) = ")" Then
        ' Remove the parentheses.
        EvaluateExpression = EvaluateExpression( _
            Mid$(expr, 2, expr_len - 2))
        Exit Function
    End If

    ' Look for -expr2.
    If Left$(expr, 1) = "-" Then
        EvaluateExpression = -EvaluateExpression( _
            Mid$(expr, 2))
        Exit Function
    End If

    ' Look for +expr2.
    If Left$(expr, 1) = "+" Then
        EvaluateExpression = EvaluateExpression( _
            Mid$(expr, 2))
        Exit Function
    End If
   
    ' Look for Fun(expr2).
    If expr_len > 5 And Right$(expr, 1) = ")" Then
        ' Find the first (.
        pos = InStr(expr, "(")

        If pos > 0 Then
            ' See what the function is.
            lexpr = LCase$(Left$(expr, pos - 1))
            rexpr = Mid$(expr, pos + 1, expr_len - pos - 1)
            Select Case lexpr
                Case "sin"
                    EvaluateExpression = Sin(EvaluateExpression(rexpr))
                    Exit Function
                Case "cos"
                    EvaluateExpression = Cos(EvaluateExpression(rexpr))
                    Exit Function
                Case "tan"
                    EvaluateExpression = Tan(EvaluateExpression(rexpr))
                    Exit Function
                Case "sqr"
                    EvaluateExpression = Sqr(EvaluateExpression(rexpr))
                    Exit Function
                Case "factorial"
                    EvaluateExpression = Factorial(EvaluateExpression(rexpr))
                    Exit Function
                ' Add other functions (including
                ' program-defined functions) here.
            End Select
        End If
    End If


   ' It must be a literal like "2.71828".
    On Error Resume Next
    EvaluateExpression = CDbl(expr)
    status = Err.Number
    On Error GoTo 0
    If status <> 0 Then
        Err.Raise status, _
            "EvaluateExpression", _
            "Error evaluating '" & expression & _
            "' as a constant."
    End If
End Function
' Return the factorial of the expression.
Private Function Factorial(ByVal Value As Double) As Double
Dim result As Double

    ' Make sure the value is an integer.
    If CLng(Value) <> Value Then
        Err.Raise vbObjectError + 1001, _
            "Factorial", _
            "Argument must be an integer in Factorial(" & _
            Format$(Value) & ")"
    End If

    result = 1
    Do While Value > 1
        result = result * Value
        Value = Value - 1
    Loop
    Factorial = result
End Function

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Expert Comment

by:JackOfPH
ID: 16899119
that a huge code ha?
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