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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: heap size exceeded for large matrices
Newsgroups: comp.lang.ada
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Date: Mon, 30 Aug 2010 11:55:02 +0200
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Date: 2010-08-30T11:55:01+02:00
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On Mon, 30 Aug 2010 07:44:00 +0000 (UTC), Natasha Kerensikova wrote:

> On 2010-08-29, Peter C. Chapin <chapinp@acm.org> wrote:
>> Be aware that you may now have to explicitly deallocate the array at
>> some point. How necessary that is will depend on your program and some
>> other factors. It's something to keep in mind.
> 
> Are there some facilities like C++'s auto_ptr (i.e. containers that
> behaves like pointers but with a reference counter, so that when the
> last container is finalized the pointed data is release automatially)?
> I haven't seen any, have I missed it?

Are you looking for a reference-counted GC or for a pointer that brings the
referenced object down with it, when goes out of scope?

> I guess it's so easy to write that if it's not standardized, it's
> probably not because of complexity. Is there something in Ada language
> or in Ada philosophy that would make them almost useless (except in rare
> situations like OP's)?

If you meant the latter, you don't need anything to write as the language
already provides collection through scoped access types (pointers).
Consider this:

with Ada.Finalization;
with Ada.Text_IO;  use Ada.Text_IO;
package P is
   type Object is new Ada.Finalization.Limited_Controlled with null record;
   overriding procedure Finalize (X : in out Object);
end P;
package body P is
   procedure Finalize (X : in out Object) is
   begin
      Put_Line ("I am down");
   end Finalize;
end P;

The object Object prints "I am down" when destroyed.

Now if you either declare an access type in a scope or else use an
anonymous type then any object allocated by new and assigned to this
pointer will be automatically destroyed when the scope is left:

   declare
      type Pointer is access all Object;
      X1 : Pointer := new Object;
      X2 : access Object := new Object;
   begin
      ... -- Using X1 and X2
   end; -- Targets of X1 and X2 are finalized and freed here

For a reference-counted GC there are several implementations of. For
example this:

http://www.dmitry-kazakov.de/ada/components.htm#Objects_etc

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de