Re: What is the difference of "with null record" and "with private"?

[Shark8 <OneWingedShark@gmail.com>]

On 23-May-14 12:19, Victor Porton wrote:
> What is the difference of "with null record" and "with private"?
>
> Both denote a descendant of a type with no new additional public fields.

Incorrect.
Null record does what you indicate, with private means that any fields 
aren't visible/public. Example:

Package Example is
     Type Parent is tagged record
         Data_1 : Integer;
     end record;

     -- Returns Data_1
     Function Get_Data (Item : Parent) return Integer;

     -- Contains Data_2, but this field is private.
     Type Child is new Parent with private;

     -- Returns Data_2
     Function Get_Data (Item : Child) return Integer;


private
     Type Child is new Parent with record
         Data_2 : Integer;
     end record;

     Function Get_Data (Item : Parent) return Integer is (Item.Data_1);
     Function Get_Data (Item : Child)  return Integer is (Item.Data_2);

End Example;