anchor.diff:  
   { TNullableDoubleRecord }
   
  -procedure TNullableDoubleRecord.CreateAsNull;
  +procedure TNullableDoubleRecord.SetNull;
   begin
     IsNull:= true;
     Value:= 0;
   end;
   
  -procedure TNullableDoubleRecord.CreateWithValue(const aValue: Double);
  +procedure TNullableDoubleRecord.SetValue(const aValue: Double);
   begin
     IsNull:= false;
     Value:= aValue;
  
positive.code: 
      function CheckIfDifferentAndAssign(const aValue : Variant) : boolean; override;
      function AsVariant: Variant; override;
      function AsString : String; override;
  
      class function StringToVariant(const aValue: String): Variant;
      class function VariantToString(const aValue: Variant): String;
  
negative.code:     Result := '';
  end;
  
  function TNullableBoolean.AsBoolean: Boolean;
  begin
    Result := (Self.NotNull) and (Self.Value);
  end;
  
  function TNullableBoolean.CheckIfDifferentAndAssign(const aValue: Variant): boolean;
  var
    tmpBool : boolean;
  