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From: lutz@iks-jena.de (Lutz Donnerhacke)
Newsgroups: comp.lang.ada
Subject: Re: Container reqs
Date: Tue, 16 Oct 2001 08:14:38 +0000 (UTC)
Organization: IKS GmbH Jena
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* Ehud Lamm wrote:
>Lutz Donnerhacke <lutz@iks-jena.de> wrote in message
>> Bute seriosly it's necessary, that the same item occurs in several
>> collections at once. It must be possible to build stacks of lists and hold
>> a task element in a list and a hash simultaniously. Good luck.
>
>So we need defaults. "take a private type and supply default named
>operations like Assign"

No. You can't get Assign on most interesting types. There is none possible.
My lib was designed to deal with this problem, but it is a first study.

>But, I think we should decide on the semantics. If you can use
>by-reference semantics, you can solv emany of these simply by
>instantiating with access types. This can be problematic, but where
>applicable cansave us a lot of trouble..

Access types are inherently dangerous. Furthermore it's not necessary to use
access types.

>> Keep them threadsafe and multiaccessed, i.e. allow the usage of active
>> Iterator to create further Iterators which in turn modify the structure.
>
>I don't see any problem with this.

  declare
     i : Iterator'Class := Get_Iterator (collection);
     j : Iterator'Class := Get_Iterator (collection);
  begin
     while not Is_Finished (i) loop
        if something then j:=i; end if;
	if foobar then callmerecursivly_in_other_task; end if;
	if someother then Delete (j); end if;
	Advance (i);
     end loop;
  end;

Do this for hashes, btrees in a multitasking enviroment without deadlocks.