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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Ravenscar vs selective wait
Date: Tue, 24 Mar 2015 06:48:27 +0000
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Date: 2015-03-24T06:48:27+00:00
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Simon Wright <simon@pushface.org> writes:

> Is it possible to construct an analog of the selective wait using the
> Ravenscar profile?
>
>    Turn_On_The_Lamp;
>    Next := Clock + Milliseconds (500);
>    select
>       accept Reset do
>          Next := Clock + Milliseconds (500);
>       end Reset;
>    or
>       delay until Next;
>       Turn_Off_The_Lamp;
>    end select;

This is rather simplified from what I want to achieve, and I can think
of an ugly solution for it.

   Turn_On_The_Lamp;
   Next := Clock + Milliseconds (500);  -- Next is a shared variable
   loop
      delay until Next;
      if Next <= Clock then
         exit;
      else
         -- something else in the program has updated Next
      end if;
   end loop;
   Turn_Off_The_Lamp;

But what if I need the next wake-up to be *earlier*?