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From: Stephen Leake <stephen.a.leake.1@gsfc.nasa.gov>
Newsgroups: comp.lang.ada
Subject: Re: Specialization
Date: 30 May 2002 15:20:56 -0400
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"Baugereau" <baugereau@ifrance.kom> writes:

> > "Baugereau" <baugereau@ifrance.kom> wrote in message
> news:<ad56du$pp4$1@wanadoo.fr>...
> > > For instance, when I empty the container, I want to Finalize all the
> > > elements if they are Controlled, and do nothing if not.
> >
> > Why wouldn't that happen automaticly? If you want to *manually*
> > control finalization, you probably shouldn't be using controlled
> > types.
> 
> I have this interface in my package (I snipped)
> 
> 
> with Ada.Finalization;
> use Ada.Finalization;
> generic
> type ELEMENT is private;
> package Vector is
> Default_Reserved : constant NATURAL := 32;
> Growth : constant NATURAL := 32;
> type ELEMENTPTR is access all ELEMENT;
> type ELEMENTS is array(NATURAL range <>) of aliased ELEMENT;

This is the problem. You should (almost certainly :) have an array of
ELEMENTPTR, not an array of ELEMENT. When an element is added to
Vector, you call 'new' for it. When an element is erased from the
vector you call an instantiation of Unchecked_Deallocation on it. Then
Finalize will be called automatically, if necessary.

See the file sal-poly-unbounded_arrays.ads
in SAL at http://users.erols.com/leakstan/Stephe/Ada/sal.html
for an example of a similar package.

You will find that you will have to allow your generic ELEMENT type to
be unconstrained and/or indefinite, if the Vector package is to be
truly useful. For example, try to define a Vector of String. Once you
do that, you are forced to have an array of pointer-to-element.

-- 
-- Stephe