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From: "Matthew Heaney" <matthew_heaney@acm.org>
Subject: Re: tasks, simple question
Date: 1999/11/15
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References: <382FC705.29121528@interact.net.au>
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In article <382FC705.29121528@interact.net.au> , G 
<Dizzy@interact.net.au>  wrote:

> What I am wondering is where and when one would use them.
>
> What sort of role they play, so to say.  What sort of things one
> would use them for.

Tasks are used for implementing concurrent abstractions.


package Philosophers is

  type Philosopher_Type (Id : Positive) is limited private;

  <ops for philosophers>

private

  -- This handles the concurrency aspects of a philosopher
  -- abstraction.
  type Philosopher_Task_Type
    (Philosopher : access Philosopher_Type);

  type Philosopher_Type (Id : Positive) is
    limited record

      <other components, probably including a protected object>

      Philosopher_Task :
        Philosopher_Task_Type (Philosopher_Type'Access);

    end record;

end Philosophers;


Here, we have a group of philosophers who all eat and think
simultaneously.  An abstraction that is concurrent will have a component
implemented as a task.




--
If we let the Creationists have their way, we may as well go whole hog.
Let us reintroduce the flat-earth theory, the chemistry of the four
elements, and mediaeval astrology.  For these outworn doctrines have
just as much claim to rival current scientific views as Creationism does
to challenge evolutionary biology.

Abusing Science: The Case Against Creationism
Philip Kitcher