309 lines
11 KiB
VB.net
309 lines
11 KiB
VB.net
''' <summary>
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''' Used to convert strings into various types.
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''' </summary>
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Public Class ScriptConversion
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Enum Associativity
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Right
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Left
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End Enum
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''' <summary>
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''' Converts an expression into a <see cref="Double"/>.
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''' </summary>
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Public Shared Function ToDouble(ByVal expression As Object) As Double
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Dim input As String = expression.ToString()
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Dim retError As Boolean = False
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Dim retDbl As Double = 0D
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retDbl = InternalToDouble(input, retError)
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If retError = False Then
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Return retDbl
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Else
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If IsArithmeticExpression(expression) = True Then
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Dim postFix As String = ToPostfix(expression.ToString())
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Return EvaluatePostfix(postFix)
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Else
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Return 0D
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End If
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End If
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End Function
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''' <summary>
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''' If the input can be evaluated into a number.
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''' </summary>
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Public Shared Function IsArithmeticExpression(ByVal expression As Object) As Boolean
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Dim retError As Boolean = False
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Dim postfix As String = ToPostfix(expression.ToString(), retError)
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If retError = False Then
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EvaluatePostfix(postfix, retError)
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Return retError = False
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Else
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Return False
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End If
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End Function
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''' <summary>
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''' Evaluates a math expression in the postfix notation. Example: "2 3 +".
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''' </summary>
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''' <param name="input">The postfix string.</param>
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Private Shared Function EvaluatePostfix(ByVal input As String, Optional ByRef hasError As Boolean = False) As Double
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Dim stack As New List(Of Double)
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Dim tokens As List(Of Char) = input.ToCharArray().ToList()
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Dim cNumber As String = ""
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While tokens.Count > 0
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Dim token As Char = tokens(0)
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tokens.RemoveAt(0)
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If IsNumber(token) = True Then
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cNumber &= token.ToString()
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ElseIf cNumber.Length > 0 Then
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stack.Insert(0, InternalToDouble(cNumber))
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cNumber = ""
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End If
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If cNumber.Length > 0 And tokens.Count = 0 Then
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stack.Insert(0, InternalToDouble(cNumber))
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cNumber = ""
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End If
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If IsOperator(token) = True Then
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If stack.Count >= 2 Then
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Dim v2 As Double = stack(0)
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Dim v1 As Double = stack(1)
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stack.RemoveAt(0)
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stack.RemoveAt(0)
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Dim result As Double = 0
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Select Case token.ToString()
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Case "+"
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result = v1 + v2
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Case "-"
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result = v1 - v2
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Case "*"
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result = v1 * v2
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Case "/"
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If v2 = 0 Then
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Logger.Log(Logger.LogTypes.Warning, "Script.vb: Cannot evaluate """ & input.ToString() & """ as an arithmetic expression.")
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hasError = True
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Return 0
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Else
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result = v1 / v2
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End If
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Case "^"
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result = v1 ^ v2
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Case "%"
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result = v1 Mod v2
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End Select
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stack.Insert(0, result)
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Else
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Logger.Log(Logger.LogTypes.Warning, "Script.vb: Cannot evaluate """ & input.ToString() & """ as an arithmetic expression.")
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hasError = True
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Return 0
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End If
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End If
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End While
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If stack.Count = 1 Then
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Return stack(0)
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Else
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Logger.Log(Logger.LogTypes.Warning, "Script.vb: Cannot evaluate """ & input.ToString() & """ as an arithmetic expression.")
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hasError = True
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Return 0
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End If
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End Function
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''' <summary>
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''' Converts an infix notation to postfix notation.
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''' </summary>
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''' <param name="input">The infix notation. Example: "2+3".</param>
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Private Shared Function ToPostfix(ByVal input As String, Optional ByRef hasError As Boolean = False) As String
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If input.Trim().StartsWith("-") Then
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input = "0" & input
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End If
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Dim tokens As List(Of Char) = input.ToCharArray().ToList()
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Dim stack As New List(Of Char)
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Dim output As String = ""
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Dim cNumber As String = ""
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While tokens.Count > 0
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Dim token As Char = tokens(0)
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tokens.RemoveAt(0)
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' Token is a number:
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If IsNumber(token) = True Then
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cNumber &= token.ToString()
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ElseIf cNumber.Length > 0 Then
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output &= cNumber.ToString() & " " ' Add to the output.
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cNumber = ""
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End If
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If cNumber.Length > 0 And tokens.Count = 0 Then
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output &= cNumber.ToString() & " "
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cNumber = ""
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End If
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' Token is an operator:
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If IsOperator(token) = True Then
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Dim o1 As Char = token
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While stack.Count > 0 AndAlso IsOperator(stack(0)) = True AndAlso ((GetAssociativity(o1) = Associativity.Left And GetPrecedence(o1) <= GetPrecedence(stack(0))) Or (GetAssociativity(o1) = Associativity.Right And GetPrecedence(o1) < GetPrecedence(stack(0))))
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output &= stack(0).ToString() & " "
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stack.RemoveAt(0)
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End While
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stack.Insert(0, o1)
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End If
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' Token is a left parenthesis:
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If token = "("c Then
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stack.Insert(0, token)
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End If
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' Token is a right parenthesis:
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If token = ")"c Then
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If stack.Count > 0 Then
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While stack.Count > 0
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If stack(0) = "("c Then
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stack.RemoveAt(0)
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Exit While
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Else
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output &= stack(0).ToString() & " "
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stack.RemoveAt(0)
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End If
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End While
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Else
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Logger.Log(Logger.LogTypes.Warning, "Script.vb: Cannot convert """ & input.ToString() & """ to an arithmetic expression.")
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hasError = True
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Return "0"
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End If
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End If
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End While
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While stack.Count > 0
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If stack(0) = "("c Or stack(0) = ")"c Then
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Logger.Log(Logger.LogTypes.Warning, "Script.vb: Cannot convert """ & input.ToString() & """ to an arithmetic expression.")
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hasError = True
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Return "0"
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Else
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output &= stack(0).ToString() & " "
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stack.RemoveAt(0)
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End If
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End While
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Return output
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End Function
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''' <summary>
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''' If the token is a number or part of one.
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''' </summary>
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''' <param name="token">The token.</param>
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Private Shared Function IsNumber(ByVal token As Char) As Boolean
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Return "0123456789.,".ToCharArray().Contains(token)
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End Function
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''' <summary>
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''' If the token is an operator.
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''' </summary>
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''' <param name="token">The token.</param>
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Private Shared Function IsOperator(ByVal token As Char) As Boolean
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Return "+-*/^%".ToCharArray().Contains(token)
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End Function
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''' <summary>
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''' Returns the precedence for an operator.
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''' </summary>
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''' <param name="[Operator]">The operator.</param>
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Private Shared Function GetPrecedence(ByVal [Operator] As Char) As Integer
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Select Case [Operator]
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Case "+"c, "-"c
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Return 2
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Case "*"c, "/"c, "%"c
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Return 3
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Case "^"c
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Return 4
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End Select
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Return -1
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End Function
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''' <summary>
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''' Returns if an operator has a Left or Right Associativity.
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''' </summary>
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''' <param name="[Operator]">The operator</param>
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Private Shared Function GetAssociativity(ByVal [Operator] As Char) As Associativity
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Select Case [Operator]
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Case "^"c
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Return Associativity.Right
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Case Else
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Return Associativity.Left
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End Select
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End Function
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''' <summary>
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''' Tries to convert a single number into a <see cref="Double"/>.
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''' </summary>
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Private Shared Function InternalToDouble(ByVal expression As String, Optional ByRef hasError As Boolean = False) As Double
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expression = expression.Replace(".", My.Application.Culture.NumberFormat.NumberDecimalSeparator)
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If StringHelper.IsNumeric(expression) Then
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Return System.Convert.ToDouble(expression)
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Else
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If expression.ToLower() = "false" Then
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Return 0
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ElseIf expression.ToLower() = "true" Then
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Return 1
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Else
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hasError = True
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Return 0
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End If
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End If
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End Function
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''' <summary>
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''' Converts an expression into an <see cref="Integer"/>.
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''' </summary>
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''' <param name="expression">The expression to convert.</param>
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Public Shared Function ToInteger(ByVal expression As Object) As Integer
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Return CInt(Math.Round(ToDouble(expression)))
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End Function
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''' <summary>
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''' Converts an expression to a <see cref="Single"/>.
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''' </summary>
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''' <param name="expression">The expression to convert.</param>
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Public Shared Function ToSingle(ByVal expression As Object) As Single
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Return CSng(ToDouble(expression))
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End Function
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''' <summary>
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''' Converts an expression into a <see cref="Boolean"/>.
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''' </summary>
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''' <param name="expression">The expression to convert.</param>
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Public Shared Function ToBoolean(ByVal expression As Object) As Boolean
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Select Case expression.ToString().ToLower()
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Case "true", "1"
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Return True
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Case Else
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Return False
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End Select
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End Function
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''' <summary>
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''' Performs a check if an expression is a valid <see cref="Boolean"/>.
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''' </summary>
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''' <param name="expression">The expression to perform the check on.</param>
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Public Shared Function IsBoolean(ByVal expression As Object) As Boolean
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Dim s As String = expression.ToString()
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Dim validBools() As String = {"0", "1", "true", "false"}
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Return validBools.Contains(s.ToLower())
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End Function
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End Class |