anchor.diff:      Result := Self.Value;
   end;
   
  +function TNullableDouble.AsFormattedString(aFormat: String): String;
  +begin
  +  if Self.IsNull then
  +    Result := ''
  +  else
  +    Result := FormatFloat(aFormat, Self.Value);
  +end;
  +
   { TNullableAnsiString }
   (*
   function TNullableAnsiString.GetValue: AnsiString;
  
positive.code:     procedure Assign(const aValue : Variant); override; overload;
  
      function CheckIfDifferentAndAssign(const aValue : Variant) : boolean; override;
      function AsVariant : Variant; override;
      function AsString : String;
  
      class function StringToVariant(const aValue : String) : Variant;
      class function VariantToString(const aValue : Variant) : String;
  
negative.code:   Result := TNullableInteger.VariantToString(Self.AsVariant);
  end;
  
  function TNullableInteger.AsFormattedString(aFormat: String): String;
  begin
    if Self.IsNull then
      Result := ''
    else
      Result := FormatFloat(aFormat, Self.Value);
  end;
  
  class function TNullableInteger.StringToVariant(const aValue: String): Variant;
  begin
    if IsNumeric(aValue, false) then
  