PRIVATE abstract data type in ADS

PRIVATE abstract data type in ADS

[Dominic D'Apice]

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 ?


ADS
---

Package reservation   is

type auto_res IS PRIVATE	
	
type reservation IS PRIVATE;
type louer       is access reservation ;

type tete_liste_louer IS PRIVATE;
type liste_louer is access tete_liste_louer ;

...

PRIVATE

type auto_res is (econo,moyenne,grande,familliale,sport,limousine);

type reservation is record
	num       : natural := 0;

	plancher  : integer := 20;
	plafond   : integer := 20;
	classe    : auto_res := econo;
	nomclient : string(1..256);
	suivant   : louer := null;
end record;


type tete_liste_louer is record
	premier  : louer := null;
	dernier  : louer := null;
	longueur : natural    := 0;			
end record;






Thanks / merci
Dominic

Re: PRIVATE abstract data type in ADS

[Pascal Obry]

"Dominic D'Apice" <dapiced@sympatico.ca> writes:

> 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 ?

Because there is nothing to hide with the access type. You just have exposed
the name and no field is accessible via the access type (except in
reservation's body of course !).

So I really don't see the problem here... or maybe I missed your point :)

Pascal.

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Re: PRIVATE abstract data type in ADS

[John English]

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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