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

[mockturtle <framefritti@gmail.com>]

On Friday, May 23, 2014 8:21:21 PM UTC+2, Victor Porton wrote:
> 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.
> > I see no difference. What is the difference and when one or another should
> > be used?
> 
> Clarification of my question: I mean the case when the full view of the type 
> is "with null record".
> 

Well, as I see it, it is more a matter of visibility.  It is true that in both cases you have the same "structure" (namely, the ancestor with no new fields), but in the case of "with private" the "users" (that is, the packages that use the derived type) do not know that...

One could say that "with private" is used to hide the internal details of your type and that if the extension is done with a "null record" there is not much to hide. Actually, I cannot imagine a case where the fact that it is public that the extension is null can cause loss of maintainability the day some new fields are added.  Nevertheless, usually I prefer the "with private" form for uniformity.

Riccardo