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Newsgroups: comp.lang.ada
Date: Wed, 6 Jan 2016 13:14:14 -0800 (PST)
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Subject: Re: Abortable Timed Action
From: Anh Vo <anhvofrcaus@gmail.com>
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Xref: news.eternal-september.org comp.lang.ada:29037
Date: 2016-01-06T13:14:14-08:00
List-Id: <comp.lang.ada>

On Thursday, December 31, 2015 at 10:09:30 AM UTC-8, T.G. wrote:
> On 2015-12-31, Anh Vo <anhvofrcaus@gmail.com> wrote:
> > I think accuracy more important than better/simpler way. There is a
> > drifting issue in your codes in term of time since delay statement
> > is involved. In addition, timer has no problem of this kind. If you
> > decide to use timer, take look at
> > http://www.adacore.com/adaanswers/gems/ada-gem-15/. Let me know if
> > have any question.
> >
> > Anh Vo
>=20
> Very nice example. I didn't know about Ada.Real_Time.Timing_Events,
> I'll probably go with that. Thanks for the pointer.

After looking at your original post again, I believe your code should work =
after replacing delay statement by delay until statement. The delay until s=
tatement does not have time drifting issue. In addition, then Entry Finish =
can be replaced by the terminate alternative. The modified version is shown=
 below.

   with Ada.Calendar; use type Ada.Calendar.Time;
   with Ada.Text_Io;  use Ada.Text_Io;
   -- ...

   -- ...
   task type Timed_Action_Task is=20
     entry Exec_After (T : Duration);=20
     entry Cancel;=20
   end Timed_Action_Task;=20

   task body Timed_Action_Task is=20
      Timeout : Duration;=20
   begin=20
      loop=20
         select=20
            accept Exec_After (T : Duration) do=20
               Timeout :=3D T;=20
            end Exec_After;=20
            select=20
               accept Cancel;=20
            or=20
               delay until (Ada.Calendar.Clock + Timeout);=20
               Put_Line ("Do Something");=20
            end select;=20
         or=20
            terminate;
         end select;=20
      end loop;=20
   end Timed_Action_Task;