Calculate Min Max of integer

[Blup]

Delphi-Quellcode:

type 
  TMyInt = record 
  private 
    FHasValue: Boolean; 
    FMax: Integer; 
    FMin: Integer; 
    FValue: Integer; 
    procedure SetValue(AValue: Integer); 
  public 
    procedure Clear;
    property HasValue: Boolean read FHasValue;
    property Max: Integer read FMax; 
    property Min: Integer read FMin; 
    property Value: Integer read FValue write SetValue; 
  end; 

type 
  TForm3 = class(TForm) 

    ButtonStart: TButton;
    ButtonStop: TButton;
    Timer1: TTimer;

    procedure ButtonStartClick(Sender: TObject);
    procedure ButtonStopClick(Sender: TObject);
    procedure Timer1Timer(Sender: TObject); 
  private 
    { Private declarations }
    FMyInit: TMyInt;
    procedure ShowMyInit;
  public 
    { Public declarations } 
  end; 

implementation 

{$R *.dfm} 

procedure TMyInt.Clear;
begin
  FHasValue := False;
  FMax      := 0;
  FMin      := 0;
  FValue    := 0;
end;

procedure TMyInt.SetValue(AValue: Integer); 
begin 
  if FHasValue then
  begin
    if FValue <> AValue then
    begin
      FValue := AValue;  

      if FMax < AValue then 
        FMax := AValue; 

      if FMin > AValue then 
        FMin := AValue; 
    end;
  end
  else
  begin    
    FHasValue := True; 
    FMax      := AValue; 
    FMin      := AValue; 
    FValue    := AValue;
  end;
end;

// usage 

procedure TForm3.ButtonStartClick(Sender: TObject);
begin
  FMyInt.Clear;
  ShowMyInit;
  Timer1.Enabled := True;
end;

procedure TForm3.ButtonStopClick(Sender: TObject);
begin
  Timer1.Enabled := False;
end;

procedure TForm3.ShowMyInit;
begin
  if FMyInt.HasValue then
    Caption := Format('Value %d  Min %d  Max %d', [FMyInt.Value, FMyInt.Min, FMyInt.Max])
  else
    Caption := 'Value    Min    Max'
end;

procedure TForm3.Timer1Timer(Sender: TObject); 
begin 
  FMyInit.Value := Random(100);
  ShowMyInit; 
end;