Re: PRIVATE abstract data type in ADS

[John English <je@brighton.ac.uk>]

Dominic D'Apice wrote:
> 
> Hi, in this abstract data type in ADS (see below), do i need to put
> 
> "type louer is access reservation" with the "IS PRIVATE" ?
> 
> If no, why i don't need to put "IS PRIVATE" after a access type when i
> want to keep it PRIVATE ?

If you had "type Lower is private" in the visible part of the package,
the only things you could do with a Lower are assignment and equality
testing (plus operations involving Lower defined in the visible part
of the package). You couldn't do any of these things:
  L : Lower := new Reservation;
  R : Reservation := L.all;
If you want package clients to be able to do this sort of thing, Lower
has to be visibly an access type. So in the end, it's up to you to
decide what you want to allow your clients to do with Lower objects...

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