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From: wojtek@power.com.pl (Wojtek Narczynski)
Newsgroups: comp.lang.ada
Subject: Re: Reprise: 'in out' parameters for functions
Date: 16 Apr 2004 04:38:02 -0700
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Date: 2004-04-16T04:38:02-07:00
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Robert,

First of all, thanks for writing me an essay. One day you might think
of gathering all your c.l.a posts into a book. I would definitely buy
a copy.

But let me push it a bit more.

> But there are two important points. First you _must_ as part of your 
> analysis of the problem domain identify the objects that need to be 
> managed. 

Analysis for generic data structures has been done decades ago. I'd
prefer to use something readily available and not redo the analysis at
this level.

But let's grant that, as a result of throughout analysis, you conclude
that you need a list that is sorted, space efficient, time efficient,
updateable from many tasks at the same time. Any hint on how to
implement this?

> protected type List is
>    procedure Append(E: in Element);
>    procedure Prepend(E: in Element);
>    ...
>    function Is_Empty return Boolean;
>    function Length return Natural;
> private
>    ...
> end List;

If you do this, only one task / thread will be able to update the data
structure.

> Should you expect to find a ready made implementation that meets your 
> needs?  Possibly.  But you almost certainly won't find it by looking for 
> libraries of protected objects. 

I found no examples of data structures with lock granularity lower
than the whole data structure.

Regards,
Wojtek