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From: Ryan Tarpine <rtarpine@hotmail.com>
Newsgroups: comp.lang.ada
Subject: Re: Hiding a type
Date: Sat, 06 Jul 2002 20:38:42 +0000
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Date: 2002-07-06T20:38:42+00:00
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Frank J. Lhota wrote:
> My recommendation would be to skip the definition of Private_Type_Ptr
> entirely, and define Public_Name as the access type:
> 
> ...

The idea is that if I have 3 kinds of nodes (N1, N2, N3) with respective 
access types, I can rename one to be the public type (Root).  All 
private functions will take N1_Ptrs, N2_Ptrs, etc.  Only the public 
functions should take a Root.  Maybe N1_Ptr is at first the root type 
but later on another node type N4 is added and now N4_Ptr should be the 
root type.  I want to make sure that all the private functions don't 
have to change; if I had skipped the definition of N1_Ptr and just used 
Root, then my private functions would have to be changed since they 
should not take a Root but instead a pointer to an N1.  They should 
always take the same type regardless of what the root type is.  Whew!  I 
hope that doesn't sound as bad to you as it does to me :)

I did just come up with a small hack, though.  I can define the root to 
be the access type and then *subtype the root type* to make the private 
type.  If the root type changes, I can then modify the private type to 
directly be an access to the original node type.  I'm writing too much 
to explain myself; that means I must be doing something wrong :) It's 
kind of ugly, but it works.

Cheers,
Ryan