Funktion löst AV aus

[fwsp]

Hallo

ich möchte ein Programm schreiben, das Delphi-Code kriegt und den in html formatiert.
ich hab auch schon ein bisschen code, den für die reservierten Wörter. Leider krieg ich immer ne AV.
kann mir jemand helfen?

Die Hufe reißt er in der Unit UMain in Zeile 40, also in der while-Schleife, hoch.

UMain:

Delphi-Quellcode:

unit UMain;
...
type
  TForm1 = class(TForm)
    Memo1: TMemo;
    Memo2: TMemo;
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
  private
    { Private-Deklarationen }
  public
    { Public-Deklarationen }
    KeyList: TStrings;
    ClassKey: String;
    ClassEnd: String;
  end;

var
  Form1: TForm1;
  iChar: Integer;

implementation

uses UReplace;

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var
  Zeile, ZeileNew: String;
begin
  Zeile := Memo1.Lines.Strings[0];

  ZeileNew := '';
  iChar := 0;
  while (iChar <= Length(Zeile)) do
  begin
    ZeileNew := ZeileNew + Replace(iChar, Zeile);
  end;

  Memo2.Text := ZeileNew;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  ClassKey := '<code class="Key">';
  ClassEnd := '</code>';

  KeyList := TStringList.Create;
  KeyList.Add('begin');
  KeyList.Add('with');
end;

end.

UReplace

Delphi-Quellcode:

unit UReplace;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

function MakeArrayOutOfDigit(Position, Length: Integer; Str: String): String;
function Replace(var Pos: Integer; Zeile: String): String;

implementation

uses UMain;

function MakeArrayOutOfDigit(Position, Length: Integer; Str: String): String;
var
  i: Integer;
begin
  Result := '';
  for i := Position to (Position + Length) do
    Result := Result + Str[i];
end;

function Replace(var Pos: Integer; Zeile: String): String;
var
  iKey: Integer;
  Replaced: Boolean;
begin
  Replaced := False;
  for iKey := 0 to (Form1.KeyList.Count - 1) do
  begin
    if (MakeArrayOutOfDigit(Pos, Length(Form1.KeyList[iKey]), Zeile) =
      Form1.KeyList[iKey])then
    begin
      Result := Form1.ClassKey +
        MakeArrayOutOfDigit(Pos, Length(Form1.KeyList[iKey]), Zeile) +
        Form1.ClassEnd;
      inc(Pos, Length(Form1.KeyList[iKey]));
      Replaced := True;
    end;
  end;

  if not Replaced then
  begin
    Result := PChar(Zeile[Pos]);
    inc(Pos);
  end;
end;

end.