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From: Matthew Heaney <matthew_heaney@acm.org>
Subject: Re: Can't hide parts of ADTs in private children
Date: 1998/11/16
Message-ID: <m3zp9smw74.fsf@mheaney.ni.net>#1/1
X-Deja-AN: 412297626
Sender: matt@mheaney.ni.net
References: <364683EB.41C6@syd.csa.com.au>
NNTP-Posting-Date: Sun, 15 Nov 1998 22:23:51 PDT
Newsgroups: comp.lang.ada
Date: 1998-11-16T00:00:00+00:00
List-Id: <comp.lang.ada>

David Bowerman <davidb@syd.csa.com.au> writes:

> I am implementing an Abstract Data Type (Class) in a package.  The code
> goes something like this:
[snip]

> Can anyone suggest another way of doing it.

Do this:

   package Class_X_Package is
 
     type Class_X is private;
     type Class_X_Ptr is access Class_X;
 
     ...  operations on objects of type X
 
   private

     type Type_A is ...;
     type Type_B is ...;
 
     type Class_X is
       record
         Component_A : Type_A;
         Component_B : Type_B;
         ...
       end record;
 
   end Class_X_Package;


If you prefer, you can declare nested packages

private

   package A_Types is

      type Type_A is private;
   ...
   end A_Types;
   use A_Types;

   package B_Types is
   
      type Type_B is private;
   ...
   end B_Types;
   use B_Types;

   type Class_X is 
      record
         Comp_A : Type_A;
         Comp_B : Type_B;
         ...
      end record;

 end Class_X_Package;