anchor.diff:    protected
       function GetTagChanged: Boolean; override;
       function GetIsNull : Boolean; override;
  -    procedure SetIsNull(aValue : Boolean); override;
  +    procedure InternalSetIsNull(aValue : Boolean); override;
     public
       constructor Create(); override;
       destructor Destroy; override;
  
positive.code:   Result := FIsNull;
  end;
  
  procedure TAbstractNullable.SetIsNull(aValue: Boolean);
  begin
    FIsNull := aValue;
  end;
  
  constructor TAbstractNullable.Create();
  begin
    FIsNull:= true;
    SetTagChanged(false);
  end;
  
  
negative.code:     FValue:= RoundToExt(AValue, FRoundingMethod, FFractionalPartDigits)
    else
      FValue:= RoundDoubleToStandardPrecision(aValue);
    InternalSetIsNull(false);
  end;
  
  constructor TNullableDouble.Create();
  