' Executable filename:  Parser.exe
'
' Author:  Br. David Carlson
'
' Date:  January 7, 2008
'
' This freeware program provides an easy-to-use, table-driven LL(1) parser for educational use.
' The user supplies the program to be parsed as an input file and supplies files containing
' tables that specify the grammar rules, the finite state machine used to chop the program up
' into tokens, etc. The output file, if parsing is successful, contains an indented form of the
' parse tree for the given input program. The program can also be used to simply break the
' program up into a list of tokens, skipping the actual parsing. The .NET framework is needed
' in order to run this program.  See the Parser.doc documentation file for further information.
'
' Revised June 2, 2008 so that nonterminals are indicated by uppercase letters, not by angle brackets
' around the nonterminals.  This allows < to be used as a logical operator if desired.
'
' Revised June 24 and 25, 2013 to give better error reporting when parsing, tokenizing, etc.
' For parsing the program tries to display the line number of the file where the error was detected
' as well as the current lookahead symbol.  Like most error reporting this is approximate.  At times
' an error is only detected when the input program reaches a certain construct, but the actual error
' is in the grammar file.  This revision also fixed a bug that sometimes caused a second or third run
' of the parser to give erroneous output in cases where the app was not shut down and restarted between
' runs.  The app should now work correctly even if left open and re-run on the same, similar, or quite
' different input.

Imports System
Imports System.IO
Imports System.Text

Public Class Form1
    Inherits System.Windows.Forms.Form

#Region " Windows Form Designer generated code "

    Public Sub New()
        MyBase.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 GroupBox1 As System.Windows.Forms.GroupBox
    Friend WithEvents RadioButtonParse As System.Windows.Forms.RadioButton
    Friend WithEvents RadioButtonFilter As System.Windows.Forms.RadioButton
    Friend WithEvents Label1 As System.Windows.Forms.Label
    Friend WithEvents ButtonRun As System.Windows.Forms.Button
    Friend WithEvents GroupBox2 As System.Windows.Forms.GroupBox
    Friend WithEvents Label7 As System.Windows.Forms.Label
    Friend WithEvents ButtonProgramFileOpen As System.Windows.Forms.Button
    Friend WithEvents ButtonProgramFileEdit As System.Windows.Forms.Button
    Friend WithEvents RadioButtonTokenize As System.Windows.Forms.RadioButton
    Friend WithEvents TextBoxProgramFile As System.Windows.Forms.TextBox
    Friend WithEvents OpenFileDialogProgram As System.Windows.Forms.OpenFileDialog
    Friend WithEvents LabelKeywordsFile As System.Windows.Forms.Label
    Friend WithEvents TextBoxKeywordsFile As System.Windows.Forms.TextBox
    Friend WithEvents ButtonKeywordsFileOpen As System.Windows.Forms.Button
    Friend WithEvents ButtonKeywordsFileEdit As System.Windows.Forms.Button
    Friend WithEvents LabelProgramFile As System.Windows.Forms.Label
    Friend WithEvents LabelFSMFile As System.Windows.Forms.Label
    Friend WithEvents LabelOutputFile As System.Windows.Forms.Label
    Friend WithEvents ButtonOutputFileEdit As System.Windows.Forms.Button
    Friend WithEvents ButtonOutputFileOpen As System.Windows.Forms.Button
    Friend WithEvents TextBoxOutputFile As System.Windows.Forms.TextBox
    Friend WithEvents ButtonFSMFileEdit As System.Windows.Forms.Button
    Friend WithEvents ButtonFSMFileOpen As System.Windows.Forms.Button
    Friend WithEvents TextBoxFSMFile As System.Windows.Forms.TextBox
    Friend WithEvents OpenFileDialogFSM As System.Windows.Forms.OpenFileDialog
    Friend WithEvents OpenFileDialogKeywords As System.Windows.Forms.OpenFileDialog
    Friend WithEvents OpenFileDialogTable As System.Windows.Forms.OpenFileDialog
    Friend WithEvents SaveFileDialogOutput As System.Windows.Forms.SaveFileDialog
    Friend WithEvents LabelMsg As System.Windows.Forms.Label
    Friend WithEvents LabelGrammarFile As System.Windows.Forms.Label
    Friend WithEvents ButtonGrammarFileEdit As System.Windows.Forms.Button
    Friend WithEvents ButtonGrammarFileOpen As System.Windows.Forms.Button
    Friend WithEvents TextBoxGrammarFile As System.Windows.Forms.TextBox
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        Me.GroupBox1 = New System.Windows.Forms.GroupBox
        Me.RadioButtonFilter = New System.Windows.Forms.RadioButton
        Me.RadioButtonParse = New System.Windows.Forms.RadioButton
        Me.RadioButtonTokenize = New System.Windows.Forms.RadioButton
        Me.Label1 = New System.Windows.Forms.Label
        Me.ButtonRun = New System.Windows.Forms.Button
        Me.LabelProgramFile = New System.Windows.Forms.Label
        Me.LabelFSMFile = New System.Windows.Forms.Label
        Me.LabelKeywordsFile = New System.Windows.Forms.Label
        Me.LabelGrammarFile = New System.Windows.Forms.Label
        Me.LabelOutputFile = New System.Windows.Forms.Label
        Me.GroupBox2 = New System.Windows.Forms.GroupBox
        Me.ButtonOutputFileEdit = New System.Windows.Forms.Button
        Me.ButtonOutputFileOpen = New System.Windows.Forms.Button
        Me.TextBoxOutputFile = New System.Windows.Forms.TextBox
        Me.ButtonGrammarFileEdit = New System.Windows.Forms.Button
        Me.ButtonGrammarFileOpen = New System.Windows.Forms.Button
        Me.TextBoxGrammarFile = New System.Windows.Forms.TextBox
        Me.ButtonKeywordsFileEdit = New System.Windows.Forms.Button
        Me.ButtonKeywordsFileOpen = New System.Windows.Forms.Button
        Me.TextBoxKeywordsFile = New System.Windows.Forms.TextBox
        Me.ButtonFSMFileEdit = New System.Windows.Forms.Button
        Me.ButtonFSMFileOpen = New System.Windows.Forms.Button
        Me.TextBoxFSMFile = New System.Windows.Forms.TextBox
        Me.ButtonProgramFileEdit = New System.Windows.Forms.Button
        Me.ButtonProgramFileOpen = New System.Windows.Forms.Button
        Me.TextBoxProgramFile = New System.Windows.Forms.TextBox
        Me.Label7 = New System.Windows.Forms.Label
        Me.OpenFileDialogProgram = New System.Windows.Forms.OpenFileDialog
        Me.OpenFileDialogFSM = New System.Windows.Forms.OpenFileDialog
        Me.OpenFileDialogKeywords = New System.Windows.Forms.OpenFileDialog
        Me.OpenFileDialogTable = New System.Windows.Forms.OpenFileDialog
        Me.SaveFileDialogOutput = New System.Windows.Forms.SaveFileDialog
        Me.LabelMsg = New System.Windows.Forms.Label
        Me.GroupBox1.SuspendLayout()
        Me.GroupBox2.SuspendLayout()
        Me.SuspendLayout()
        '
        'GroupBox1
        '
        Me.GroupBox1.Controls.Add(Me.RadioButtonFilter)
        Me.GroupBox1.Controls.Add(Me.RadioButtonParse)
        Me.GroupBox1.Controls.Add(Me.RadioButtonTokenize)
        Me.GroupBox1.ForeColor = System.Drawing.Color.RoyalBlue
        Me.GroupBox1.Location = New System.Drawing.Point(256, 8)
        Me.GroupBox1.Name = "GroupBox1"
        Me.GroupBox1.Size = New System.Drawing.Size(280, 72)
        Me.GroupBox1.TabIndex = 0
        Me.GroupBox1.TabStop = False
        Me.GroupBox1.Text = "Mode of Operation"
        '
        'RadioButtonFilter
        '
        Me.RadioButtonFilter.Location = New System.Drawing.Point(120, 32)
        Me.RadioButtonFilter.Name = "RadioButtonFilter"
        Me.RadioButtonFilter.Size = New System.Drawing.Size(48, 24)
        Me.RadioButtonFilter.TabIndex = 2
        Me.RadioButtonFilter.Text = "Filter"
        '
        'RadioButtonParse
        '
        Me.RadioButtonParse.Checked = True
        Me.RadioButtonParse.Location = New System.Drawing.Point(208, 32)
        Me.RadioButtonParse.Name = "RadioButtonParse"
        Me.RadioButtonParse.Size = New System.Drawing.Size(56, 24)
        Me.RadioButtonParse.TabIndex = 1
        Me.RadioButtonParse.TabStop = True
        Me.RadioButtonParse.Text = "Parse"
        '
        'RadioButtonTokenize
        '
        Me.RadioButtonTokenize.Location = New System.Drawing.Point(24, 32)
        Me.RadioButtonTokenize.Name = "RadioButtonTokenize"
        Me.RadioButtonTokenize.Size = New System.Drawing.Size(72, 24)
        Me.RadioButtonTokenize.TabIndex = 0
        Me.RadioButtonTokenize.Text = "Tokenize"
        '
        'Label1
        '
        Me.Label1.Font = New System.Drawing.Font("Microsoft Sans Serif", 8.25!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.Label1.ForeColor = System.Drawing.Color.RoyalBlue
        Me.Label1.Location = New System.Drawing.Point(16, 40)
        Me.Label1.Name = "Label1"
        Me.Label1.Size = New System.Drawing.Size(208, 48)
        Me.Label1.TabIndex = 1
        Me.Label1.Text = "Select mode of operation, supply needed filenames, and click on Run. Then check t" & _
            "he output file."
        '
        'ButtonRun
        '
        Me.ButtonRun.Enabled = False
        Me.ButtonRun.ForeColor = System.Drawing.Color.RoyalBlue
        Me.ButtonRun.Location = New System.Drawing.Point(576, 40)
        Me.ButtonRun.Name = "ButtonRun"
        Me.ButtonRun.Size = New System.Drawing.Size(75, 23)
        Me.ButtonRun.TabIndex = 2
        Me.ButtonRun.Text = "Run"
        '
        'LabelProgramFile
        '
        Me.LabelProgramFile.Font = New System.Drawing.Font("Microsoft Sans Serif", 8.25!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.LabelProgramFile.ForeColor = System.Drawing.Color.RoyalBlue
        Me.LabelProgramFile.Location = New System.Drawing.Point(16, 37)
        Me.LabelProgramFile.Name = "LabelProgramFile"
        Me.LabelProgramFile.Size = New System.Drawing.Size(80, 16)
        Me.LabelProgramFile.TabIndex = 3
        Me.LabelProgramFile.Text = "Program file:"
        '
        'LabelFSMFile
        '
        Me.LabelFSMFile.Font = New System.Drawing.Font("Microsoft Sans Serif", 8.25!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.LabelFSMFile.ForeColor = System.Drawing.Color.RoyalBlue
        Me.LabelFSMFile.Location = New System.Drawing.Point(16, 79)
        Me.LabelFSMFile.Name = "LabelFSMFile"
        Me.LabelFSMFile.Size = New System.Drawing.Size(80, 16)
        Me.LabelFSMFile.TabIndex = 4
        Me.LabelFSMFile.Text = "FSM file:"
        '
        'LabelKeywordsFile
        '
        Me.LabelKeywordsFile.Font = New System.Drawing.Font("Microsoft Sans Serif", 8.25!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.LabelKeywordsFile.ForeColor = System.Drawing.Color.RoyalBlue
        Me.LabelKeywordsFile.Location = New System.Drawing.Point(16, 115)
        Me.LabelKeywordsFile.Name = "LabelKeywordsFile"
        Me.LabelKeywordsFile.Size = New System.Drawing.Size(80, 16)
        Me.LabelKeywordsFile.TabIndex = 5
        Me.LabelKeywordsFile.Text = "Keywords file:"
        '
        'LabelGrammarFile
        '
        Me.LabelGrammarFile.Font = New System.Drawing.Font("Microsoft Sans Serif", 8.25!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.LabelGrammarFile.ForeColor = System.Drawing.Color.RoyalBlue
        Me.LabelGrammarFile.Location = New System.Drawing.Point(16, 159)
        Me.LabelGrammarFile.Name = "LabelGrammarFile"
        Me.LabelGrammarFile.Size = New System.Drawing.Size(80, 16)
        Me.LabelGrammarFile.TabIndex = 6
        Me.LabelGrammarFile.Text = "Grammar file:"
        '
        'LabelOutputFile
        '
        Me.LabelOutputFile.Font = New System.Drawing.Font("Microsoft Sans Serif", 8.25!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.LabelOutputFile.ForeColor = System.Drawing.Color.RoyalBlue
        Me.LabelOutputFile.Location = New System.Drawing.Point(16, 197)
        Me.LabelOutputFile.Name = "LabelOutputFile"
        Me.LabelOutputFile.Size = New System.Drawing.Size(80, 16)
        Me.LabelOutputFile.TabIndex = 7
        Me.LabelOutputFile.Text = "Output file:"
        '
        'GroupBox2
        '
        Me.GroupBox2.Controls.Add(Me.ButtonOutputFileEdit)
        Me.GroupBox2.Controls.Add(Me.ButtonOutputFileOpen)
        Me.GroupBox2.Controls.Add(Me.TextBoxOutputFile)
        Me.GroupBox2.Controls.Add(Me.ButtonGrammarFileEdit)
        Me.GroupBox2.Controls.Add(Me.ButtonGrammarFileOpen)
        Me.GroupBox2.Controls.Add(Me.TextBoxGrammarFile)
        Me.GroupBox2.Controls.Add(Me.ButtonKeywordsFileEdit)
        Me.GroupBox2.Controls.Add(Me.ButtonKeywordsFileOpen)
        Me.GroupBox2.Controls.Add(Me.TextBoxKeywordsFile)
        Me.GroupBox2.Controls.Add(Me.ButtonFSMFileEdit)
        Me.GroupBox2.Controls.Add(Me.ButtonFSMFileOpen)
        Me.GroupBox2.Controls.Add(Me.TextBoxFSMFile)
        Me.GroupBox2.Controls.Add(Me.ButtonProgramFileEdit)
        Me.GroupBox2.Controls.Add(Me.ButtonProgramFileOpen)
        Me.GroupBox2.Controls.Add(Me.TextBoxProgramFile)
        Me.GroupBox2.Controls.Add(Me.LabelGrammarFile)
        Me.GroupBox2.Controls.Add(Me.LabelFSMFile)
        Me.GroupBox2.Controls.Add(Me.LabelKeywordsFile)
        Me.GroupBox2.Controls.Add(Me.LabelProgramFile)
        Me.GroupBox2.Controls.Add(Me.LabelOutputFile)
        Me.GroupBox2.ForeColor = System.Drawing.Color.RoyalBlue
        Me.GroupBox2.Location = New System.Drawing.Point(16, 88)
        Me.GroupBox2.Name = "GroupBox2"
        Me.GroupBox2.Size = New System.Drawing.Size(656, 232)
        Me.GroupBox2.TabIndex = 8
        Me.GroupBox2.TabStop = False
        Me.GroupBox2.Text = "Files"
        '
        'ButtonOutputFileEdit
        '
        Me.ButtonOutputFileEdit.Enabled = False
        Me.ButtonOutputFileEdit.ForeColor = System.Drawing.Color.RoyalBlue
        Me.ButtonOutputFileEdit.Location = New System.Drawing.Point(560, 194)
        Me.ButtonOutputFileEdit.Name = "ButtonOutputFileEdit"
        Me.ButtonOutputFileEdit.Size = New System.Drawing.Size(75, 23)
        Me.ButtonOutputFileEdit.TabIndex = 22
        Me.ButtonOutputFileEdit.Text = "Edit"
        '
        'ButtonOutputFileOpen
        '
        Me.ButtonOutputFileOpen.ForeColor = System.Drawing.Color.RoyalBlue
        Me.ButtonOutputFileOpen.Location = New System.Drawing.Point(464, 194)
        Me.ButtonOutputFileOpen.Name = "ButtonOutputFileOpen"
        Me.ButtonOutputFileOpen.Size = New System.Drawing.Size(75, 23)
        Me.ButtonOutputFileOpen.TabIndex = 21
        Me.ButtonOutputFileOpen.Text = "Open"
        '
        'TextBoxOutputFile
        '
        Me.TextBoxOutputFile.ForeColor = System.Drawing.SystemColors.ActiveCaption
        Me.TextBoxOutputFile.Location = New System.Drawing.Point(104, 195)
        Me.TextBoxOutputFile.Name = "TextBoxOutputFile"
        Me.TextBoxOutputFile.Size = New System.Drawing.Size(344, 20)
        Me.TextBoxOutputFile.TabIndex = 20
        '
        'ButtonGrammarFileEdit
        '
        Me.ButtonGrammarFileEdit.Enabled = False
        Me.ButtonGrammarFileEdit.ForeColor = System.Drawing.Color.RoyalBlue
        Me.ButtonGrammarFileEdit.Location = New System.Drawing.Point(560, 156)
        Me.ButtonGrammarFileEdit.Name = "ButtonGrammarFileEdit"
        Me.ButtonGrammarFileEdit.Size = New System.Drawing.Size(75, 23)
        Me.ButtonGrammarFileEdit.TabIndex = 19
        Me.ButtonGrammarFileEdit.Text = "Edit"
        '
        'ButtonGrammarFileOpen
        '
        Me.ButtonGrammarFileOpen.ForeColor = System.Drawing.Color.RoyalBlue
        Me.ButtonGrammarFileOpen.Location = New System.Drawing.Point(464, 156)
        Me.ButtonGrammarFileOpen.Name = "ButtonGrammarFileOpen"
        Me.ButtonGrammarFileOpen.Size = New System.Drawing.Size(75, 23)
        Me.ButtonGrammarFileOpen.TabIndex = 18
        Me.ButtonGrammarFileOpen.Text = "Open"
        '
        'TextBoxGrammarFile
        '
        Me.TextBoxGrammarFile.ForeColor = System.Drawing.SystemColors.ActiveCaption
        Me.TextBoxGrammarFile.Location = New System.Drawing.Point(104, 157)
        Me.TextBoxGrammarFile.Name = "TextBoxGrammarFile"
        Me.TextBoxGrammarFile.Size = New System.Drawing.Size(344, 20)
        Me.TextBoxGrammarFile.TabIndex = 17
        '
        'ButtonKeywordsFileEdit
        '
        Me.ButtonKeywordsFileEdit.Enabled = False
        Me.ButtonKeywordsFileEdit.ForeColor = System.Drawing.Color.RoyalBlue
        Me.ButtonKeywordsFileEdit.Location = New System.Drawing.Point(560, 112)
        Me.ButtonKeywordsFileEdit.Name = "ButtonKeywordsFileEdit"
        Me.ButtonKeywordsFileEdit.Size = New System.Drawing.Size(75, 23)
        Me.ButtonKeywordsFileEdit.TabIndex = 16
        Me.ButtonKeywordsFileEdit.Text = "Edit"
        '
        'ButtonKeywordsFileOpen
        '
        Me.ButtonKeywordsFileOpen.ForeColor = System.Drawing.Color.RoyalBlue
        Me.ButtonKeywordsFileOpen.Location = New System.Drawing.Point(464, 112)
        Me.ButtonKeywordsFileOpen.Name = "ButtonKeywordsFileOpen"
        Me.ButtonKeywordsFileOpen.Size = New System.Drawing.Size(75, 23)
        Me.ButtonKeywordsFileOpen.TabIndex = 15
        Me.ButtonKeywordsFileOpen.Text = "Open"
        '
        'TextBoxKeywordsFile
        '
        Me.TextBoxKeywordsFile.ForeColor = System.Drawing.SystemColors.ActiveCaption
        Me.TextBoxKeywordsFile.Location = New System.Drawing.Point(104, 113)
        Me.TextBoxKeywordsFile.Name = "TextBoxKeywordsFile"
        Me.TextBoxKeywordsFile.Size = New System.Drawing.Size(344, 20)
        Me.TextBoxKeywordsFile.TabIndex = 14
        '
        'ButtonFSMFileEdit
        '
        Me.ButtonFSMFileEdit.Enabled = False
        Me.ButtonFSMFileEdit.ForeColor = System.Drawing.Color.RoyalBlue
        Me.ButtonFSMFileEdit.Location = New System.Drawing.Point(560, 76)
        Me.ButtonFSMFileEdit.Name = "ButtonFSMFileEdit"
        Me.ButtonFSMFileEdit.Size = New System.Drawing.Size(75, 23)
        Me.ButtonFSMFileEdit.TabIndex = 13
        Me.ButtonFSMFileEdit.Text = "Edit"
        '
        'ButtonFSMFileOpen
        '
        Me.ButtonFSMFileOpen.ForeColor = System.Drawing.Color.RoyalBlue
        Me.ButtonFSMFileOpen.Location = New System.Drawing.Point(464, 76)
        Me.ButtonFSMFileOpen.Name = "ButtonFSMFileOpen"
        Me.ButtonFSMFileOpen.Size = New System.Drawing.Size(75, 23)
        Me.ButtonFSMFileOpen.TabIndex = 12
        Me.ButtonFSMFileOpen.Text = "Open"
        '
        'TextBoxFSMFile
        '
        Me.TextBoxFSMFile.ForeColor = System.Drawing.SystemColors.ActiveCaption
        Me.TextBoxFSMFile.Location = New System.Drawing.Point(104, 77)
        Me.TextBoxFSMFile.Name = "TextBoxFSMFile"
        Me.TextBoxFSMFile.Size = New System.Drawing.Size(344, 20)
        Me.TextBoxFSMFile.TabIndex = 11
        '
        'ButtonProgramFileEdit
        '
        Me.ButtonProgramFileEdit.Enabled = False
        Me.ButtonProgramFileEdit.ForeColor = System.Drawing.Color.RoyalBlue
        Me.ButtonProgramFileEdit.Location = New System.Drawing.Point(560, 34)
        Me.ButtonProgramFileEdit.Name = "ButtonProgramFileEdit"
        Me.ButtonProgramFileEdit.Size = New System.Drawing.Size(75, 23)
        Me.ButtonProgramFileEdit.TabIndex = 10
        Me.ButtonProgramFileEdit.Text = "Edit"
        '
        'ButtonProgramFileOpen
        '
        Me.ButtonProgramFileOpen.ForeColor = System.Drawing.Color.RoyalBlue
        Me.ButtonProgramFileOpen.Location = New System.Drawing.Point(464, 34)
        Me.ButtonProgramFileOpen.Name = "ButtonProgramFileOpen"
        Me.ButtonProgramFileOpen.Size = New System.Drawing.Size(75, 23)
        Me.ButtonProgramFileOpen.TabIndex = 9
        Me.ButtonProgramFileOpen.Text = "Open"
        '
        'TextBoxProgramFile
        '
        Me.TextBoxProgramFile.ForeColor = System.Drawing.SystemColors.ActiveCaption
        Me.TextBoxProgramFile.Location = New System.Drawing.Point(104, 35)
        Me.TextBoxProgramFile.Name = "TextBoxProgramFile"
        Me.TextBoxProgramFile.Size = New System.Drawing.Size(344, 20)
        Me.TextBoxProgramFile.TabIndex = 8
        '
        'Label7
        '
        Me.Label7.Font = New System.Drawing.Font("Microsoft Sans Serif", 8.25!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.Label7.ForeColor = System.Drawing.Color.RoyalBlue
        Me.Label7.Location = New System.Drawing.Point(16, 16)
        Me.Label7.Name = "Label7"
        Me.Label7.Size = New System.Drawing.Size(208, 16)
        Me.Label7.TabIndex = 9
        Me.Label7.Text = "Parser freeware by Br. David Carlson"
        '
        'OpenFileDialogProgram
        '
        Me.OpenFileDialogProgram.Filter = "Text files (*.txt)|*.txt"
        Me.OpenFileDialogProgram.ShowReadOnly = True
        Me.OpenFileDialogProgram.Title = "Open Program File"
        '
        'OpenFileDialogFSM
        '
        Me.OpenFileDialogFSM.Title = "Open FSM File"
        '
        'OpenFileDialogKeywords
        '
        Me.OpenFileDialogKeywords.Title = "Open Keywords File"
        '
        'OpenFileDialogTable
        '
        Me.OpenFileDialogTable.Title = "Open Grammar File"
        '
        'SaveFileDialogOutput
        '
        Me.SaveFileDialogOutput.Title = "Save Output File"
        '
        'LabelMsg
        '
        Me.LabelMsg.Font = New System.Drawing.Font("Microsoft Sans Serif", 8.25!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.LabelMsg.ForeColor = System.Drawing.Color.Red
        Me.LabelMsg.Location = New System.Drawing.Point(16, 328)
        Me.LabelMsg.Name = "LabelMsg"
        Me.LabelMsg.Size = New System.Drawing.Size(635, 53)
        Me.LabelMsg.TabIndex = 10
        '
        'Form1
        '
        Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
        Me.ClientSize = New System.Drawing.Size(680, 381)
        Me.Controls.Add(Me.LabelMsg)
        Me.Controls.Add(Me.Label7)
        Me.Controls.Add(Me.GroupBox2)
        Me.Controls.Add(Me.ButtonRun)
        Me.Controls.Add(Me.Label1)
        Me.Controls.Add(Me.GroupBox1)
        Me.Name = "Form1"
        Me.Text = "Parser 1.2"
        Me.GroupBox1.ResumeLayout(False)
        Me.GroupBox2.ResumeLayout(False)
        Me.GroupBox2.PerformLayout()
        Me.ResumeLayout(False)

    End Sub

#End Region

    Private Const ArraySize As Integer = 600
    Private Const MaxStates As Integer = 200
    Private Const MaxCategories As Integer = 40
    Private Const MaxLookAheads As Integer = 40
    Private Const MaxNonTerminals As Integer = 200
    Private Const MaxRules As Integer = 300
    Private Const MaxRuleLength As Integer = 24
    Private Const MaxKeywords As Integer = 200
    Private Const MaxChar As Integer = 24

    Private OutputFileStreamWriter As StreamWriter
    Private ProgramArray As String()
    Private FSMArray As String()
    Private GrammarArray As String()
    Private KeywordsArray As String()
    Private TokenAccepted As String()
    Private Categories As String()
    Private FSMTable As Integer(,)
    Private LookAheads As TokenClass()
    Private NonTerminals As String()
    Private RuleTable As Integer(,)
    Private Rules As RuleClass()
    Private NumStates As Integer
    Private NumCategories As Integer
    Private ChIndex As Integer
    Private FSMSize As Integer
    Private GrammarSize As Integer
    Private NumLines As Integer
    Private NumKeywords As Integer
    Private NumLookAheads As Integer
    Private NumNonTerminals As Integer
    Private NumRules As Integer
    Private Token As TokenClass
    Private CharIsSaved As Boolean
    Private SavedChar As Char

    ' Get the next char from ProgramArray into Ch, adjusting the rest of the parameters as needed.
    ' If there is a saved char, it is used instead of getting a new char from ProgramArray.
    ' Ch is the returned char, Status contains a string giving the status of the char Ch,
    ' Line is the current string from ProgramArray to look at to get the next char,
    ' LineNumber is the index of this string in ProgramArray, ChIndex is the index of where
    ' to get the next char in Line, and Len is the length of Line.
    Private Sub NextChar(ByRef Ch As Char, ByRef Status As String, ByRef Line As String, _
        ByRef LineNumber As Integer, ByRef ChIndex As Integer, ByRef Len As Integer)

        Dim Classify As Boolean

        Ch = " "   ' Use blank char as default value.
        Classify = False
        If CharIsSaved Then
            CharIsSaved = False
            Ch = SavedChar
            ChIndex = ChIndex + 1
            Classify = True
        ElseIf (LineNumber = NumLines - 1) And (ChIndex = Len) Then
            Status = "eof"
            LineNumber = NumLines
        ElseIf (ChIndex = Len) Then ' We are at the end of a line other than the last line.
            Status = "whitespace"   ' whitespace includes space char and eoln.
            LineNumber = LineNumber + 1
            Line = ProgramArray(LineNumber)
            Len = Line.Length
            ChIndex = 0
        Else
            Ch = Line.Chars(ChIndex)
            ChIndex = ChIndex + 1
            Classify = True
        End If

        If Classify Then
            If Char.IsDigit(Ch) Then
                Status = "digit"
            ElseIf Char.IsLetter(Ch) Then
                Status = "alpha"
            ElseIf Ch = ":"c Then
                Status = "colon"
            ElseIf Ch = "="c Then
                Status = "equals"
            ElseIf Ch = ";" Then
                Status = "semicolon"
            ElseIf Ch = " "c Then
                Status = "whitespace"
            ElseIf Ch = "+"c Then
                Status = "plus"
            ElseIf Ch = "-"c Then
                Status = "minus"
            ElseIf Ch = "*"c Then
                Status = "asterisk"
            ElseIf Ch = "/"c Then
                Status = "slash"
            ElseIf Ch = "!"c Then
                Status = "exclamation"
            ElseIf Ch = "&"c Then
                Status = "ampersand"
            ElseIf Ch = "("c Then
                Status = "leftparen"
            ElseIf Ch = ")"c Then
                Status = "rightparen"
            ElseIf Ch = "'"c Then
                Status = "singlequote"
            ElseIf Ch = """"c Then
                Status = "doublequote"
            ElseIf Ch = ","c Then
                Status = "comma"
            ElseIf Ch = "."c Then
                Status = "period"
            ElseIf Ch = "<"c Then
                Status = "lessthan"
            ElseIf Ch = ">"c Then
                Status = "greaterthan"
            ElseIf Ch = "`"c Then
                Status = "tilde"
            ElseIf Ch = "`"c Then
                Status = "backquote"
            ElseIf Ch = "@"c Then
                Status = "at"
            ElseIf Ch = "#"c Then
                Status = "pound"
            ElseIf Ch = "$"c Then
                Status = "dollar"
            ElseIf Ch = "%"c Then
                Status = "percent"
            ElseIf Ch = "^"c Then
                Status = "caret"
            ElseIf Ch = "_"c Then
                Status = "underscore"
            ElseIf Ch = "|"c Then
                Status = "pipe"
            ElseIf Ch = "\"c Then
                Status = "backslash"
            ElseIf Ch = "["c Then
                Status = "leftbracket"
            ElseIf Ch = "]"c Then
                Status = "rightbracket"
            ElseIf Ch = "{"c Then
                Status = "leftbrace"
            ElseIf Ch = "}"c Then
                Status = "rightbrace"
            ElseIf Ch = "?"c Then
                Status = "question"
            Else
                Status = "other"
            End If
        End If
    End Sub

    ' Find the next state based on the present value of State and Status of current input.
    ' Uses FSMTable from the Form1 object.
    ' Return this new state in parameter State.
    Private Sub NextState(ByRef State As Integer, ByVal Status As String)
        Dim Found As Boolean
        Dim Column As Integer

        If (State < 1) Or (State > NumStates) Then
            State = -1   ' Indicates an error.
        Else
            Column = 0
            Found = False
            While (Column < NumCategories) And (Not Found)
                If Status = Categories(Column) Then
                    Found = True
                Else
                    Column = Column + 1
                End If
            End While
            If Found Then
                State = FSMTable(State - 1, Column)
            Else
                State = -1   ' Indicates an error.
            End If
        End If
    End Sub

    ' Checks to see if the current value of Token.Item is in KeywordsArray.  If so,
    ' Token.Category is changed to the string keyword.  Otherwise it is changed to the
    ' string identifier.
    Private Sub KeywordCheck()
        Dim k As Integer
        Dim Found As Boolean

        k = 0
        Found = False
        While (k < NumKeywords) And (Not Found)
            If KeywordsArray(k) = Token.Item Then
                Found = True
            Else
                k = k + 1
            End If
        End While

        If Found Then
            Token.Category = "keyword"
        Else
            Token.Category = "identifier"
        End If
    End Sub

    ' Retrieves the next token, placing it in the Token field of the Form1 object.
    ' The data for the token is taken from ProgramArray (and possibly SavedChar),
    ' starting at line LineNumber of ProgramArray and index ChIndex within this line.
    ' This routines advances ChIndex and LineNumber as needed so that they point to
    ' the location in ProgramArray right after the retrieved token.
    ' The information in the FSM file (stored in the FSMArray and associated variables)
    ' is used to determine what is a valid token and what category it fits.
    Private Sub NextToken(ByRef LineNumber As Integer, ByRef ChIndex As Integer)

        Dim CharCount, State, OldState, Len As Integer
        Dim Status, Line As String
        Dim Ch As Char

        If LineNumber < NumLines Then
            CharCount = 0
            State = 1
            Token.Item = ""
            Token.Category = ""
            Line = ProgramArray(LineNumber)
            Len = Line.Length
            Do
                OldState = State
                NextChar(Ch, Status, Line, LineNumber, ChIndex, Len)
                If (Status <> "whitespace") And (Status <> "eof") Then
                    CharCount = CharCount + 1
                    If CharCount >= MaxChar Then
                        Throw New IndexOutOfRangeException("Too many chars for token in program file line " & (LineNumber + 1).ToString)
                    End If
                    Token.Item = Token.Item & Ch
                End If
                NextState(State, Status)
            Loop Until (State = 0) Or (State = -1)

            If State = 0 Then   ' A token was successfully found.
                If (Status <> "whitespace") And (Status <> "eof") Then   ' We recorded 1 char too many.
                    Token.Item = Token.Item.Substring(0, CharCount - 1)   ' Remove the last char ...
                    SavedChar = Ch   ' ... and save it.
                    ChIndex = ChIndex - 1
                    CharIsSaved = True
                End If
                Token.Category = TokenAccepted(OldState - 1)
                If (Not RadioButtonTokenize.Checked) And (Token.Category = "word") Then
                    KeywordCheck()
                End If
            Else   ' State = -1
                Token.Category = "error"
            End If
        Else
            Token.Item = ""
            Token.Category = "EndMarker"
        End If
    End Sub

    ' Finds the next integer within string Str starting at index Position.
    ' Skips over initial whitespace, if need be, to find this integer.
    ' Returns this integer in parameter Item and returns the index after it in Position.
    ' Throws an exception if it cannot find a valid integer.
    ' Negative integers are not handled.
    Private Sub NextInt(ByVal Str As String, ByRef Position As Integer, ByRef Item As Integer)
        Dim k, Len, Sign As Integer
        Dim Ch As Char

        Len = Str.Length
        k = Position
        If Position < Len Then
            Ch = Str.Chars(k)
        Else
            Throw New ArithmeticException("Not a valid number")
        End If

        While (Ch <> "-"c) And (Not Char.IsDigit(Ch)) And (k < Len)
            k = k + 1
            If k < Len Then
                Ch = Str.Chars(k)
            End If
        End While

        If k = Len Then
            Throw New ArithmeticException("Not a valid number")
        ElseIf (Ch = "-"c) Then
            If k = Len - 1 Then
                Throw New ArithmeticException("Not a valid number")
            Else
                k = k + 1
                Ch = Str.Chars(k)
                If (Not Char.IsDigit(Ch)) Then
                    Throw New ArithmeticException("Not a valid number")
                Else
                    Sign = -1
                End If
            End If
        Else   ' We must have a digit for Ch
            Sign = 1
        End If

        Item = 0
        While Char.IsDigit(Ch) And (k < Len)
            Item = Item * 10 + Val(Ch)
            k = k + 1
            If k < Len Then
                Ch = Str.Chars(k)
            End If
        End While

        Item = Sign * Item
        Position = k
    End Sub

    ' Returns in Item the substring found starting at Index in Str.  Item will be the
    ' empty string if Str at Index is a blank or doesn't exist.  The substring stops
    ' just before the first blank (or end of string Str).  Index is normally advanced
    ' to the position of the char in Str just after the end of Item.  Index always
    ' advances by at least 1, unless Str itself is the emtpy string.
    Private Sub NextString(ByVal Str As String, ByRef Index As Integer, ByRef Item As String)
        Dim [Continue] As Boolean
        Dim Len, Count As Integer
        Dim Ch As Char

        Item = ""
        Len = Str.Length()
        [Continue] = True
        Count = 0

        While (Index < Len) And [Continue]
            Ch = Str.Chars(Index)
            If Ch = " "c Then
                [Continue] = False
            ElseIf Count >= MaxChar - 1 Then
                Throw New IndexOutOfRangeException("Too many chars for the string")
            Else
                Item = Item & Ch
                Count = Count + 1
            End If
            Index = Index + 1
        End While
    End Sub

    ' Advances Index to skip over blank characters at position Index and following in string Str.
    ' Index is advanced to the position of the first non-blank at or following the starting
    ' location given by Index.  If there is no non-blank in this section, Index is
    ' set to 1 more than the last valid index for the string Str.
    Private Sub SkipBlanks(ByVal Str As String, ByRef Index As Integer)
        Dim Ch As Char
        Dim [Continue] As Boolean
        Dim Len As Integer

        Len = Str.Length()
        [Continue] = True
        While (Index < Len) And [Continue]
            Ch = Str.Chars(Index)
            If Ch = " "c Then
                Index = Index + 1
            Else
                [Continue] = False
            End If
        End While
    End Sub

    ' Reads the lines of the FSM file into the field FSMArray.  Also places the count of the
    ' number of these lines into the field FSMSize.
    Private Sub ReadFSMFile()
        Dim k As Integer
        Dim Line As String
        Dim FSMFileStreamReader As StreamReader

        Try
            k = 0
            FSMFileStreamReader = New StreamReader(TextBoxFSMFile.Text)
            FSMArray = New String(ArraySize - 1) {}
            Do
                Line = FSMFileStreamReader.ReadLine()
                FSMArray(k) = Line
                k = k + 1
            Loop Until (Line Is Nothing) Or (k = ArraySize)
            FSMSize = k
        Catch Except As Exception
            Throw New Exception("Error in FSM file line " & (k + 1).ToString & ": " & Except.Message)
        Finally
            FSMFileStreamReader.Close()
        End Try
    End Sub

    ' Reads the lines of the grammar file into the field GrammarArray.  Also places the count of the
    ' number of these lines into the field GrammarSize.
    Private Sub ReadGrammarFile()
        Dim k As Integer
        Dim Line As String
        Dim GrammarFileStreamReader As StreamReader

        Try
            k = 0
            GrammarFileStreamReader = New StreamReader(TextBoxGrammarFile.Text)
            GrammarArray = New String(ArraySize - 1) {}
            Do
                Line = GrammarFileStreamReader.ReadLine()
                GrammarArray(k) = Line
                k = k + 1
            Loop Until (Line Is Nothing) Or (k = ArraySize)
            GrammarSize = k
        Catch Except As Exception
            Throw New Exception("Error in grammar file line " & (k + 1).ToString & ": " & Except.Message)
        Finally
            GrammarFileStreamReader.Close()
        End Try
    End Sub

    ' Extracts the data from the field GrammarArray, placing it into the fields NumLookAheads,
    ' NumNonTerminals, NumRules, LookAheads, NonTerminals, Rules, and RuleTable.
    ' Revised June 2, 2008 so that nonterminals are indicated by uppercase letters, not by angle brackets
    ' around the nonterminals.  This allows < to be used as a logical operator if desired.
    Private Sub ExtractGrammarData()
        Dim Start, Num, Row, Col, RuleLength As Integer
        Dim Line, Item, Category, NonTerminal, TempString, BodyPart As String

        Try
            Start = 0
            Num = 0
            NextInt(GrammarArray(0), Start, NumLookAheads)
            If (NumLookAheads < 1) Or (NumLookAheads > MaxLookAheads) Then
                Throw New IndexOutOfRangeException("In grammar file invalid num lookaheads " & NumLookAheads.ToString)
            End If

            LookAheads = New TokenClass(NumLookAheads - 1) {}
            For Row = 1 To NumLookAheads
                Num = Num + 1
                Line = GrammarArray(Num)
                Start = 0
                NextString(Line, Start, Item)
                SkipBlanks(Line, Start)
                NextString(Line, Start, Category)
                LookAheads(Row - 1) = New TokenClass(Item, Category)
            Next
            Num = Num + 1

            While (Num < GrammarSize) And (GrammarArray(Num) = "")
                Num = Num + 1
            End While

            If Num >= GrammarSize Then
                Throw New IndexOutOfRangeException("Can't find int for num nonterminals in grammar file")
            End If

            Start = 0
            NextInt(GrammarArray(Num), Start, NumNonTerminals)
            If (NumNonTerminals < 1) Or (NumNonTerminals > MaxNonTerminals) Then
                Throw New IndexOutOfRangeException("In grammar file invalid num nonterminals " & NumNonTerminals.ToString)
            End If

            NonTerminals = New String(NumNonTerminals - 1) {}
            RuleTable = New Integer(NumNonTerminals - 1, NumLookAheads - 1) {}
            For Row = 0 To NumNonTerminals - 1
                Num = Num + 1
                Line = GrammarArray(Num)
                Start = 0
                NextString(Line, Start, NonTerminal)
                NonTerminals(Row) = NonTerminal
                For Col = 0 To NumLookAheads - 1
                    NextInt(Line, Start, RuleTable(Row, Col))
                Next
            Next
            Num = Num + 1

            While (Num < GrammarSize) And (GrammarArray(Num) = "")
                Num = Num + 1
            End While

            If Num >= GrammarSize Then
                Throw New IndexOutOfRangeException("Can't find integer for num grammar rules")
            End If

            Start = 0
            NextInt(GrammarArray(Num), Start, NumRules)
            If (NumRules < 1) Or (NumRules > MaxRules) Then
                Throw New IndexOutOfRangeException("Invalid num grammar rules " & NumRules.ToString)
            End If

            Rules = New RuleClass(NumRules - 1) {}

            For Row = 0 To NumRules - 1
                Num = Num + 1
                Line = GrammarArray(Num)
                If Line Is Nothing Then
                    Throw New IndexOutOfRangeException("Line " & (Num + 1).ToString & " from grammar file is empty")
                End If
                Start = 0
                NextString(Line, Start, TempString)   ' Ignore the rule number
                SkipBlanks(Line, Start)
                NextString(Line, Start, TempString)   ' Ignore the head of the rule
                SkipBlanks(Line, Start)
                NextString(Line, Start, TempString)   ' Ignore the ->
                NextInt(Line, Start, RuleLength)
                If (RuleLength < 0) Or (RuleLength > MaxRuleLength) Then
                    Throw New IndexOutOfRangeException("Invalid number " & RuleLength.ToString & " in RHS of grammar rule " & (Num + 1).ToString)
                End If

                Rules(Row) = New RuleClass(RuleLength)
                Rules(Row).RuleBodyArray = New TokenClass(RuleLength - 1) {}

                For Col = 0 To RuleLength - 1
                    SkipBlanks(Line, Start)
                    NextString(Line, Start, BodyPart)
                    If Char.IsUpper(BodyPart, 0) Then      ' Modified June 2, 2008
                        Category = "nonterminal"
                    Else
                        Category = "terminal"
                    End If
                    Rules(Row).RuleBodyArray(Col) = New TokenClass(BodyPart, Category)
                Next
            Next
        Catch Except As Exception
            Throw New Exception("Error in grammar file line " & (Num + 1).ToString & ": " & Except.Message)
        End Try
    End Sub

    ' Extracts the data from the field FSMArray, placing it into the fields NumStates,
    ' TokenAccepted, NumCategories, Categories, and FSMTable.
    Private Sub ExtractFSMData()
        Dim Start, Num, Row, Col, Index, Item As Integer
        Dim Line As String

        Try
            Start = 0
            Num = 0
            NextInt(FSMArray(0), Start, NumStates)
            If (NumStates < 1) Or (NumStates > MaxStates) Then
                Throw New IndexOutOfRangeException("In FSM file invalid num states " & NumStates.ToString)
            End If

            TokenAccepted = New String(NumStates - 1) {}
            For Row = 1 To NumStates
                Num = Num + 1
                If FSMArray(Num).Length > MaxChar Then
                    Throw New IndexOutOfRangeException("Too many chars for a token in FSM file")
                End If
                TokenAccepted(Row - 1) = FSMArray(Num)
            Next
            Num = Num + 1

            While (Num < FSMSize) And (FSMArray(Num) = "")
                Num = Num + 1
            End While

            If Num >= FSMSize Then
                Throw New IndexOutOfRangeException("Can't find integer for num categories in FSM file")
            End If

            Start = 0
            NextInt(FSMArray(Num), Start, NumCategories)
            If (NumCategories < 1) Or (NumCategories > MaxCategories) Then
                Throw New IndexOutOfRangeException("In FSM file invalid num categories " & NumCategories.ToString)
            End If

            Categories = New String(NumCategories - 1) {}
            For Col = 1 To NumCategories
                Num = Num + 1
                If FSMArray(Num).Length > MaxChar Then
                    Throw New IndexOutOfRangeException("Too many chars for a category in FSM file")
                End If
                Categories(Col - 1) = FSMArray(Num)
            Next
            Num = Num + 1

            While (Num < FSMSize) And (FSMArray(Num) = "")
                Num = Num + 1
            End While
            Num = Num + 1   ' Skip the comment line.

            If Num >= FSMSize Then
                Throw New IndexOutOfRangeException("Can't find first integer for FSM transition table")
            End If

            FSMTable = New Integer(NumStates - 1, NumCategories - 1) {}
            For Row = 0 To NumStates - 1
                Line = FSMArray(Num)
                Num = Num + 1
                Index = 0
                NextInt(Line, Index, Item)
                FSMTable(Row, 0) = Item
                For Col = 1 To NumCategories - 1
                    NextInt(Line, Index, Item)
                    FSMTable(Row, Col) = Item
                Next
            Next
        Catch Except As Exception
            Throw New Exception("Error in FSM file line " & (Num + 1).ToString & ": " & Except.Message)
        End Try
    End Sub

    ' Reads the program file lines into the field ProgramArray.  Also places the count of the
    ' number of such lines into the field NumLines.
    Private Sub ReadProgramFile()
        Dim k As Integer
        Dim Line As String
        Dim ProgramFileStreamReader As StreamReader

        Try
            k = 0
            ProgramFileStreamReader = New StreamReader(TextBoxProgramFile.Text)
            ProgramArray = New String(ArraySize - 1) {}
            Do
                Line = ProgramFileStreamReader.ReadLine()
                ProgramArray(k) = Line
                k = k + 1
            Loop Until (Line Is Nothing) Or (k = ArraySize)
            If Line Is Nothing Then
                NumLines = k - 1
            Else
                NumLines = k
            End If
        Catch Except As Exception
            Throw New Exception("Error in program file line " & (k + 1).ToString & ": " & Except.Message)
        Finally
            ProgramFileStreamReader.Close()
        End Try
    End Sub

    ' Reads the keywords file lines into the field KeywordsArray.  Also places the count of the
    ' number of such keywords into the field NumKeywords.
    Private Sub ReadKeywordsFile()
        Dim k, Start As Integer
        Dim Line As String
        Dim KeywordsFileStreamReader As StreamReader

        Try
            k = 0
            Start = 0
            KeywordsFileStreamReader = New StreamReader(TextBoxKeywordsFile.Text)
            KeywordsArray = New String(MaxKeywords - 1) {}
            Line = KeywordsFileStreamReader.ReadLine()   ' First line has count of number of keywords.
            NextInt(Line, Start, NumKeywords)
            If (NumKeywords < 0) Or (NumKeywords > MaxKeywords) Then
                Throw New IndexOutOfRangeException("In keywords file invalid num keywords " & NumKeywords.ToString)
            End If

            For k = 1 To NumKeywords
                Line = KeywordsFileStreamReader.ReadLine()
                If (Line Is Nothing) Then
                    Throw New Exception("Couldn't read keyword " & k.ToString & " in keywords file")
                Else
                    KeywordsArray(k - 1) = Line
                End If
            Next
        Catch Except As Exception
            Throw New Exception("Error in keywords file line " & k.ToString & ": " & Except.Message)
        Finally
            KeywordsFileStreamReader.Close()
        End Try
    End Sub

    ' Finds LookAheadSymbol in the LookAheads field, and finds StackNonTerminal in the
    ' NonTerminals field.  Returns the rule number of the grammar rule from RuleTable
    ' that corresponds to LookAheadSymbol and StackNonTerminal.  If either of the two
    ' lookups fails, 0 (an invalid rule number) is returned as the value of RuleNumber.
    Private Sub FindRule(ByRef LookAheadSymbol As TokenClass, ByRef StackNonTerminal As String, _
        ByRef RuleNumber As Integer)

        Dim Row, Col As Integer
        Dim Found As Boolean

        Try
            ' Find LookAheadSymbol in LookAheads array.
            Col = 0
            Found = False
            While (Col < NumLookAheads) And (Not Found)
                If LookAheads(Col).Category = LookAheadSymbol.Category Then
                    If (LookAheads(Col).Category = "special") Or _
                        (LookAheads(Col).Category = "keyword") Then   ' Need items to match too.
                        If LookAheads(Col).Item = LookAheadSymbol.Item Then
                            Found = True
                        Else
                            Col = Col + 1
                        End If
                    Else
                        Found = True
                    End If
                Else
                    Col = Col + 1
                End If
            End While

            If Not Found Then
                RuleNumber = 0
                Return
            End If

            ' Find StackNonTerminal in NonTerminals array.
            Row = 0
            Found = False
            While (Row < NumNonTerminals) And (Not Found)
                If NonTerminals(Row) = StackNonTerminal Then
                    Found = True
                Else
                    Row = Row + 1
                End If
            End While

            If Not Found Then
                RuleNumber = 0
                Return
            End If

            ' Get the rule number.
            RuleNumber = RuleTable(Row, Col)
        Catch Except As Exception   ' Modified June 24, 2013
            Throw New Exception("No grammar rule found to use. Lookahead " & AdjustString(LookAheadSymbol.Item) & "/" & LookAheadSymbol.Category)
        End Try
    End Sub

    ' Print the contents of the StackInfo item with appropriate indenting.
    Private Sub Print(ByRef StackInfo As StackInfoClass)
        Dim k As Integer

        For k = 1 To StackInfo.NumTabs
            OutputFileStreamWriter.Write("   ")
        Next
        OutputFileStreamWriter.Write(StackInfo.Token.Item)
    End Sub

    ' Convert any possible empty string so it can be seen, but leave other strings alone.
    ' Added June 24, 2013
    Private Function AdjustString(ByVal Str As String) As String
        If (Str.Length = 0) Then
            Return "<empty string>"
        Else
            Return Str
        End If
    End Function

    ' Process the data and write the results to the output file.
    ' If tokenize or filter was the operation selected, tokens are grabbed from the program
    ' data in ProgramArray and written in readable form to the output file.
    ' If parse was the operation selected, the program data from ProgramArray is parsed (if
    ' possible) using the rules found in RuleTable and an indented form of the parse tree
    ' is written to the output file.  Modified June 24, 2013 to include more detailed
    ' error reporting.
    Private Sub WriteOutputFile()
        Dim Num As Integer
        Num = 0
        If RadioButtonParse.Checked Then   ' Parsing is the operation that was selected.
            Try
                Dim S As Stack
                Dim StartToken As TokenClass
                Dim StackInfo, NewStackInfo As StackInfoClass
                Dim RuleNumber, k As Integer

                CharIsSaved = False   ' This line and the next added June 24, 2013.
                SavedChar = " "
                S = New Stack(24)
                StartToken = New TokenClass("PROGRAM", "nonterminal")   ' Modified June 2, 2008
                StackInfo = New StackInfoClass(StartToken, 0)
                S.Push(StackInfo)
                OutputFileStreamWriter = New StreamWriter(TextBoxOutputFile.Text)
                ChIndex = 0
                Token = New TokenClass("", "")   ' We will overwrite Token with new info each time we get a new token.
                NextToken(Num, ChIndex)

                While (S.Count > 0)
                    StackInfo = S.Pop()
                    Print(StackInfo)
                    If StackInfo.Token.Category = "terminal" Then
                        OutputFileStreamWriter.Write("   ")
                        If Token.Category = "EndMarker" Then   ' Cannot match.
                            OutputFileStreamWriter.WriteLine()
                            OutputFileStreamWriter.WriteLine("Parsing failed. End of program file reached. Item popped was " & AdjustString(StackInfo.Token.Item))
                            Throw New Exception("Parsing failed")
                        ElseIf (Token.Category = "identifier") Or (Token.Category = "number") Then
                            OutputFileStreamWriter.Write(Token.Item)
                            If Token.Category = StackInfo.Token.Item Then
                                NextToken(Num, ChIndex)
                            Else
                                OutputFileStreamWriter.WriteLine()
                                OutputFileStreamWriter.WriteLine("Parsing failed. Program file line " & (Num + 1).ToString & " Item popped was " & AdjustString(StackInfo.Token.Item) & " and does not match lookahead " & AdjustString(Token.Category))
                                Throw New Exception("Parsing failed")
                            End If
                        ElseIf Token.Item = StackInfo.Token.Item Then
                            NextToken(Num, ChIndex)
                        Else
                            OutputFileStreamWriter.WriteLine()
                            OutputFileStreamWriter.WriteLine("Parsing failed. Program file line " & (Num + 1).ToString & " Item popped was " & AdjustString(StackInfo.Token.Item) & " and does not match lookahead " & AdjustString(Token.Item))
                            Throw New Exception("Parsing failed")
                        End If
                        OutputFileStreamWriter.WriteLine()
                    Else   ' StackInfo.Token.Category is "nonterminal"
                        OutputFileStreamWriter.WriteLine()
                        FindRule(Token, StackInfo.Token.Item, RuleNumber)
                        If RuleNumber = 0 Then
                            OutputFileStreamWriter.WriteLine()
                            OutputFileStreamWriter.WriteLine("Parsing failed, no matching rule. Program file line " & (Num + 1).ToString & " Item popped was " & AdjustString(StackInfo.Token.Item) & " and lookahead was " & AdjustString(Token.Item))
                            Throw New Exception("Parsing failed")
                        Else   ' Push the parts of the rule body in backwards order.
                            For k = Rules(RuleNumber - 1).RuleBodyLength - 1 To 0 Step -1
                                NewStackInfo = New StackInfoClass(Rules(RuleNumber - 1).RuleBodyArray(k), _
                                    StackInfo.NumTabs + 1)
                                S.Push(NewStackInfo)
                            Next
                        End If
                    End If
                End While

                If Token.Category = "EndMarker" Then
                    OutputFileStreamWriter.WriteLine()
                    OutputFileStreamWriter.WriteLine("Parsing succeeded")
                Else
                    OutputFileStreamWriter.WriteLine()
                    OutputFileStreamWriter.WriteLine("Parsing failed. The stack is empty but we have not reached the end of the program file, now at line " & (Num + 1).ToString)
                    Throw New Exception("Parsing failed")
                End If
            Catch Except As Exception
                Throw New Exception("Error in program file line " & (Num + 1).ToString & ": " & Except.Message)
            Finally
                OutputFileStreamWriter.Close()
            End Try
        Else   ' Tokenize or filter was the selected operation.
            Try
                OutputFileStreamWriter = New StreamWriter(TextBoxOutputFile.Text)
                Token = New TokenClass("", "")
                ChIndex = 0
                Do
                    NextToken(Num, ChIndex)
                    OutputFileStreamWriter.WriteLine(Token.ToString)
                Loop Until (Token.Category = "EndMarker") Or (Num >= NumLines)
            Catch Except As Exception
                Throw New Exception("Error in program file line " & (Num + 1).ToString & ": " & Except.Message)
            Finally
                OutputFileStreamWriter.Close()
            End Try
        End If
    End Sub

    ' Adjust which items on the form are enabled and which are grayed out.
    Private Sub AdjustForm()
        LabelMsg.Text = ""
        If RadioButtonFilter.Checked Then
            LabelKeywordsFile.Enabled = True
            TextBoxKeywordsFile.Enabled = True
            ButtonKeywordsFileOpen.Enabled = True
            LabelGrammarFile.Enabled = False
            TextBoxGrammarFile.Enabled = False
            ButtonGrammarFileOpen.Enabled = False
            If (TextBoxKeywordsFile.Text = "") Or (TextBoxProgramFile.Text = "") _
                Or (TextBoxFSMFile.Text = "") Or (TextBoxOutputFile.Text = "") Then
                ButtonRun.Enabled = False
            Else
                ButtonRun.Enabled = True
            End If
        ElseIf RadioButtonTokenize.Checked Then
            LabelKeywordsFile.Enabled = False
            TextBoxKeywordsFile.Enabled = False
            ButtonKeywordsFileOpen.Enabled = False
            LabelGrammarFile.Enabled = False
            TextBoxGrammarFile.Enabled = False
            ButtonGrammarFileOpen.Enabled = False
            If (TextBoxProgramFile.Text = "") Or (TextBoxFSMFile.Text = "") _
                Or (TextBoxOutputFile.Text = "") Then
                ButtonRun.Enabled = False
            Else
                ButtonRun.Enabled = True
            End If
        Else   ' Radio button for parse is checked.
            LabelKeywordsFile.Enabled = True
            TextBoxKeywordsFile.Enabled = True
            ButtonKeywordsFileOpen.Enabled = True
            LabelGrammarFile.Enabled = True
            TextBoxGrammarFile.Enabled = True
            ButtonGrammarFileOpen.Enabled = True
            If (TextBoxGrammarFile.Text = "") Or (TextBoxKeywordsFile.Text = "") _
                Or (TextBoxProgramFile.Text = "") Or (TextBoxFSMFile.Text = "") _
                Or (TextBoxOutputFile.Text = "") Then
                ButtonRun.Enabled = False
            Else
                ButtonRun.Enabled = True
            End If
        End If

        If TextBoxProgramFile.Text = "" Then
            ButtonProgramFileEdit.Enabled = False
        Else
            ButtonProgramFileEdit.Enabled = True
        End If

        If TextBoxFSMFile.Text = "" Then
            ButtonFSMFileEdit.Enabled = False
        Else
            ButtonFSMFileEdit.Enabled = True
        End If

        If TextBoxOutputFile.Text = "" Then
            ButtonOutputFileEdit.Enabled = False
        Else
            ButtonOutputFileEdit.Enabled = True
        End If

        If (TextBoxKeywordsFile.Text = "") Or (RadioButtonTokenize.Checked) Then
            ButtonKeywordsFileEdit.Enabled = False
        Else
            ButtonKeywordsFileEdit.Enabled = True
        End If

        If (TextBoxGrammarFile.Text = "") Or (RadioButtonTokenize.Checked) Or (RadioButtonFilter.Checked) Then
            ButtonGrammarFileEdit.Enabled = False
        Else
            ButtonGrammarFileEdit.Enabled = True
        End If
    End Sub

    Private Sub ButtonProgramFileEdit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ButtonProgramFileEdit.Click
        LabelMsg.Text = ""
        System.Diagnostics.Process.Start("Notepad.exe", TextBoxProgramFile.Text)
    End Sub

    Private Sub ButtonProgramFileOpen_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ButtonProgramFileOpen.Click
        LabelMsg.Text = ""
        If (OpenFileDialogProgram.ShowDialog() = DialogResult.OK) Then
            TextBoxProgramFile.Text = OpenFileDialogProgram.FileName
        End If
    End Sub

    Private Sub RadioButtonParse_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RadioButtonParse.CheckedChanged
        AdjustForm()
    End Sub

    Private Sub RadioButtonFilter_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RadioButtonFilter.CheckedChanged
        AdjustForm()
    End Sub

    Private Sub RadioButtonTokenize_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RadioButtonTokenize.CheckedChanged
        AdjustForm()
    End Sub

    Private Sub ButtonFSMFileOpen_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ButtonFSMFileOpen.Click
        LabelMsg.Text = ""
        If (OpenFileDialogFSM.ShowDialog() = DialogResult.OK) Then
            TextBoxFSMFile.Text = OpenFileDialogFSM.FileName
        End If
    End Sub

    Private Sub ButtonFSMFileEdit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ButtonFSMFileEdit.Click
        LabelMsg.Text = ""
        System.Diagnostics.Process.Start("Notepad.exe", TextBoxFSMFile.Text)
    End Sub

    Private Sub ButtonKeywordsFileOpen_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ButtonKeywordsFileOpen.Click
        LabelMsg.Text = ""
        If (OpenFileDialogKeywords.ShowDialog() = DialogResult.OK) Then
            TextBoxKeywordsFile.Text = OpenFileDialogKeywords.FileName
        End If
    End Sub

    Private Sub ButtonKeywordsFileEdit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ButtonKeywordsFileEdit.Click
        LabelMsg.Text = ""
        System.Diagnostics.Process.Start("Notepad.exe", TextBoxKeywordsFile.Text)
    End Sub

    Private Sub ButtonTableFileOpen_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ButtonGrammarFileOpen.Click
        LabelMsg.Text = ""
        If (OpenFileDialogTable.ShowDialog() = DialogResult.OK) Then
            TextBoxGrammarFile.Text = OpenFileDialogTable.FileName
        End If
    End Sub

    Private Sub ButtonTableFileEdit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ButtonGrammarFileEdit.Click
        LabelMsg.Text = ""
        System.Diagnostics.Process.Start("Notepad.exe", TextBoxGrammarFile.Text)
    End Sub

    Private Sub ButtonOutputFileOpen_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ButtonOutputFileOpen.Click
        LabelMsg.Text = ""
        If (SaveFileDialogOutput.ShowDialog() = DialogResult.OK) Then
            TextBoxOutputFile.Text = SaveFileDialogOutput.FileName
        End If
    End Sub

    Private Sub ButtonOutputFileEdit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ButtonOutputFileEdit.Click
        LabelMsg.Text = ""
        System.Diagnostics.Process.Start("Notepad.exe", TextBoxOutputFile.Text)
    End Sub

    Private Sub TextBoxProgramFile_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBoxProgramFile.TextChanged
        LabelMsg.Text = ""
        AdjustForm()
    End Sub

    Private Sub TextBoxFSMFile_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBoxFSMFile.TextChanged
        LabelMsg.Text = ""
        AdjustForm()
    End Sub

    Private Sub TextBoxKeywordsFile_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBoxKeywordsFile.TextChanged
        LabelMsg.Text = ""
        AdjustForm()
    End Sub

    Private Sub TextBoxTableFile_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBoxGrammarFile.TextChanged
        LabelMsg.Text = ""
        AdjustForm()
    End Sub

    Private Sub TextBoxOutputFile_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBoxOutputFile.TextChanged
        LabelMsg.Text = ""
        AdjustForm()
    End Sub

    ' The main action starts when the user clicks on the Run button.  This click handler 
    ' for the Run button farms out the work to the appropriate routines.
    Private Sub ButtonRun_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ButtonRun.Click
        LabelMsg.Text = ""
        Try
            ReadFSMFile()
            ExtractFSMData()
            ReadProgramFile()
            If Not RadioButtonTokenize.Checked Then
                ReadKeywordsFile()
            End If
            If RadioButtonParse.Checked Then
                ReadGrammarFile()
                ExtractGrammarData()
            End If
            WriteOutputFile()
        Catch Except As Exception
            LabelMsg.Text = Except.Message
        End Try
    End Sub

End Class