REM written by Daniel R. Spohn
'This text is filler
'sdfdsfsdfsdf
'10/02/03



Option Strict On

Public Class Homework3
    Inherits System.Windows.Forms.Form


#Region " Windows Form Designer generated code "

    Public Sub New()



        'This call is required by the Windows Form Designer.
        InitializeComponent()

        'Add any initialization after the InitializeComponent() call

    End Sub

    'Form overrides dispose to clean up the component list.
    Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing Then
            If Not (components Is Nothing) Then
                components.Dispose()
            End If
        End If
        MyBase.Dispose(disposing)
    End Sub

    'Required by the Windows Form Designer
    Private components As System.ComponentModel.IContainer

    'NOTE: The following procedure is required by the Windows Form Designer
    'It can be modified using the Windows Form Designer.  
    'Do not modify it using the code editor.
    Friend WithEvents txtInput As System.Windows.Forms.TextBox
    Friend WithEvents btnCalculate As System.Windows.Forms.Button
    Friend WithEvents lblCalculated As System.Windows.Forms.Label
    Friend WithEvents MainMenu1 As System.Windows.Forms.MainMenu
    Friend WithEvents mnuFile As System.Windows.Forms.MenuItem
    Friend WithEvents mnuHelp As System.Windows.Forms.MenuItem
    Friend WithEvents mnuFileClear As System.Windows.Forms.MenuItem
    Friend WithEvents mnuFileExit As System.Windows.Forms.MenuItem
    Friend WithEvents mnuHelpAbout As System.Windows.Forms.MenuItem
    Friend WithEvents ToolTip1 As System.Windows.Forms.ToolTip
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        Me.components = New System.ComponentModel.Container()
        Me.txtInput = New System.Windows.Forms.TextBox()
        Me.btnCalculate = New System.Windows.Forms.Button()
        Me.lblCalculated = New System.Windows.Forms.Label()
        Me.MainMenu1 = New System.Windows.Forms.MainMenu()
        Me.mnuFile = New System.Windows.Forms.MenuItem()
        Me.mnuFileClear = New System.Windows.Forms.MenuItem()
        Me.mnuFileExit = New System.Windows.Forms.MenuItem()
        Me.mnuHelp = New System.Windows.Forms.MenuItem()
        Me.mnuHelpAbout = New System.Windows.Forms.MenuItem()
        Me.ToolTip1 = New System.Windows.Forms.ToolTip(Me.components)
        Me.SuspendLayout()
        '
        'txtInput
        '
        Me.txtInput.Location = New System.Drawing.Point(56, 32)
        Me.txtInput.Name = "txtInput"
        Me.txtInput.Size = New System.Drawing.Size(304, 20)
        Me.txtInput.TabIndex = 0
        Me.txtInput.Text = ""
        Me.ToolTip1.SetToolTip(Me.txtInput, "Enter an Expression such as ""5+3"" or ""20 \ 5 * 2""")
        '
        'btnCalculate
        '
        Me.btnCalculate.Location = New System.Drawing.Point(168, 120)
        Me.btnCalculate.Name = "btnCalculate"
        Me.btnCalculate.Size = New System.Drawing.Size(80, 32)
        Me.btnCalculate.TabIndex = 1
        Me.btnCalculate.Text = "&Calculate"
        '
        'lblCalculated
        '
        Me.lblCalculated.BorderStyle = System.Windows.Forms.BorderStyle.Fixed3D
        Me.lblCalculated.Location = New System.Drawing.Point(128, 80)
        Me.lblCalculated.Name = "lblCalculated"
        Me.lblCalculated.Size = New System.Drawing.Size(160, 16)
        Me.lblCalculated.TabIndex = 2
        '
        'MainMenu1
        '
        Me.MainMenu1.MenuItems.AddRange(New System.Windows.Forms.MenuItem() {Me.mnuFile, Me.mnuHelp})
        '
        'mnuFile
        '
        Me.mnuFile.Index = 0
        Me.mnuFile.MenuItems.AddRange(New System.Windows.Forms.MenuItem() {Me.mnuFileClear, Me.mnuFileExit})
        Me.mnuFile.Text = "&File"
        '
        'mnuFileClear
        '
        Me.mnuFileClear.Index = 0
        Me.mnuFileClear.Text = "&Clear"
        '
        'mnuFileExit
        '
        Me.mnuFileExit.Index = 1
        Me.mnuFileExit.Text = "E&xit"
        '
        'mnuHelp
        '
        Me.mnuHelp.Index = 1
        Me.mnuHelp.MenuItems.AddRange(New System.Windows.Forms.MenuItem() {Me.mnuHelpAbout})
        Me.mnuHelp.Text = "&Help"
        '
        'mnuHelpAbout
        '
        Me.mnuHelpAbout.Index = 0
        Me.mnuHelpAbout.Text = "&About"
        '
        'Homework3
        '
        Me.AcceptButton = Me.btnCalculate
        Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
        Me.ClientSize = New System.Drawing.Size(416, 181)
        Me.Controls.AddRange(New System.Windows.Forms.Control() {Me.lblCalculated, Me.btnCalculate, Me.txtInput})
        Me.Menu = Me.MainMenu1
        Me.Name = "Homework3"
        Me.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen
        Me.Text = "Integer Arithmetic"
        Me.ResumeLayout(False)

    End Sub

#End Region
    Dim mintStart As Integer = 1
    Dim mintIndex As Integer = 1
    Dim mstrOperator As String
    Dim blnError As Boolean = False


    Private Function ValidInput(ByVal A As String) As Boolean
        'This function calls the RemoveSpaces function and the Invalid Characters function
        Dim blnValid As Boolean
        Dim strSpacesRemoved As String
        If InvalidCharacters(txtInput.Text) > 0 Then
            blnValid = False
        Else
            txtInput.Text = RemoveSpaces(txtInput.Text)
            blnValid = True


        End If
        Return blnValid
    End Function

    Private Function RemoveSpaces(ByVal A As String) As String
        'this function removes uneeded spaces from the expression
        Dim IntIndex As Integer = 1
        Dim NewString As String

        For IntIndex = 1 To A.Length
            If " " <> A.Substring(IntIndex - 1, 1) Then
                NewString &= A.Substring(IntIndex - 1, 1)
            End If

        Next
        Return NewString
    End Function

    Private Function InvalidCharacters(ByVal A As String) As Integer
        'This Function Checks the Expression for invalid characters
        Dim intIndex As Integer = 1
        Dim intReturn As Integer
        Dim intLength As Integer = A.Length



        While (intIndex <= intLength)
            If (Strings.InStr("+-*\^0123456789 ", A.Substring(intIndex - 1, 1), 0) = 0) Then
                mintStart = intIndex - 1
                intReturn = intIndex
            End If
            intIndex += 1
        End While
        Return intReturn
    End Function

    Private Function GetOperand(ByVal A As String) As Integer
        'This function gets the first operand
        Dim StrCharacter As String = ""
        Dim StrOperand As String
        Dim IntOperand As Integer

        Do Until ((mintIndex - 1) = A.Length)
            StrCharacter = A.Substring(mintIndex - 1, 1)
            Select Case StrCharacter
                Case "+", "-"
                    If mintIndex = 1 Then
                        StrOperand = StrCharacter
                    Else
                        Return IntOperand
                    End If
                Case "0", "1", "2", "3", "4", "5", "6", "7", "8", "9"
                    StrOperand &= StrCharacter
                    Try
                        IntOperand = CInt(StrOperand)
                    Catch myErr As OverflowException
                        MessageBox.Show("Number to Large to be Calculated")
                        blnError = True
                        mintIndex = A.Length
                    End Try
                Case Else
                    'mintAnswer = IntOperand
                    Return IntOperand


            End Select
            mintIndex += 1



        Loop
        Return IntOperand

    End Function

    Private Function GetOperatorthenOperand(ByVal A As String) As Integer
        'This function gets and operator, then an operand
        If blnError = False Then


            Dim strCharacter As String
            strCharacter = A.Substring(mintIndex - 1, 1)
            mstrOperator = strCharacter
            mintIndex += 1
            Dim StrOperand As String
            Dim intOperand As Integer
            Dim blnOperand As Boolean = False

            Do Until ((mintIndex - 1) = A.Length)
                strCharacter = A.Substring(mintIndex - 1, 1)
                Select Case strCharacter
                    Case "+", "-"
                        If blnOperand = False Then
                            StrOperand = strCharacter
                        Else
                            Return intOperand
                        End If
                    Case "0", "1", "2", "3", "4", "5", "6", "7", "8", "9"
                        StrOperand &= strCharacter
                        Try
                            intOperand = CInt(StrOperand)
                        Catch myErr As OverflowException
                            MessageBox.Show("Number to Large to be Calculated")
                            blnError = True
                        End Try
                        blnOperand = True

                    Case Else
                        Return intOperand

                End Select
                mintIndex += 1
            Loop
            Return intOperand
        End If



    End Function

    Private Function EvaluateExpression(ByVal A As String) As Integer
        ' this expression calls getoperand and getoperatorthenoperand functions
        ' Also it decides whether to add, subtract, divide or multiply the operands
        If blnError = False Then
            Dim intOperand1 As Integer
            Try

                intOperand1 = GetOperand(A)
                Do Until ((mintIndex - 1) = A.Length)
                    Dim intOperand2 As Integer = 0
                    intOperand2 = GetOperatorthenOperand(A)
                    Select Case mstrOperator
                        Case "+"
                            intOperand1 = intOperand1 + intOperand2
                        Case "-"
                            intOperand1 = intOperand1 - intOperand2
                        Case "\"
                            intOperand1 = intOperand1 \ intOperand2
                        Case "*"
                            intOperand1 = intOperand1 * intOperand2
                        Case "^"
                            intOperand1 = CInt(intOperand1 ^ intOperand2)
                    End Select
                Loop
            Catch myErr As OverflowException
                MessageBox.Show("Number to Large to be Calculated")
                blnError = True
                Exit Function
            Catch myErr As DivideByZeroException
                MessageBox.Show("Cannot Divide by Zero")
                blnError = True
                Exit Function

            End Try
            Return intOperand1

        End If
    End Function

    Private Sub mnuFileClear_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles mnuFileClear.Click
        lblCalculated.Text = ""
        With txtInput
            .Clear()
            .Focus()
        End With

    End Sub

    Private Sub mnuFileExit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles mnuFileExit.Click
        Me.Close()
    End Sub

    Private Sub mnuHelpAbout_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles mnuHelpAbout.Click
        MessageBox.Show("This Program was written by: Daniel R. Spohn")
    End Sub

    Private Sub btnCalculate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCalculate.Click
        Dim strInput As String
        If ValidInput(txtInput.Text) Then
            strInput = txtInput.Text
            strInput = CStr(EvaluateExpression(strInput))
            If blnError = False Then
                lblCalculated.Text = strInput
            End If

        Else
            MessageBox.Show("Invalid Input- Please Enter Only Operands and Operators")
            With txtInput
                .Select(mintStart, 1)
                .Focus()
            End With
        End If
        mintIndex = 1
        blnError = False

    End Sub

End Class