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Date: Sat, 30 Oct 2010 21:20:04 +0200
From: Georg Bauhaus <rm-host.bauhaus@maps.futureapps.de>
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Subject: Re: Do people who use Ada also use ocaml or F#?
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Date: 2010-10-30T21:20:04+02:00
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On 10/30/10 8:58 PM, Yannick Duchêne (Hibou57) wrote:
> Le Sat, 30 Oct 2010 16:12:44 +0200, Niklas Holsti <niklas.holsti@tidorum.invalid> a écrit:
>> I hesitate to say so, Yannick, but what you say above makes we wonder if you really know what sort of "yield" is proposed for Ada 2012. As I understand the proposed Ada 2012 Yield procedures, they are meant for low-level control of task scheduling
> Oops, not the Yield I know :(
> Sorry everyones for the Oops (doubly disappointed)
>
> (seems I miss-understood Randy when he talked about this Yield some days ago)
>

For programming an "'incremental' return statement", as
Niklas Holsti has put it, I find the original, 30 years old
"architectural" notion of task quite well suited.

Forget about number of processors, task switching, or
anything "heavy" for a moment.  Let a task just be some
sequential process that computes something incrementally.
The task object accepts calls whenever it is ready
to deliver another result.  Call this result the yield,
the result that the task has most recently generated:


    task type Generator is
       entry Element (Result : out T);
    end Generator;

    task body Generator is
       Data : array (Data_Index) of T;
    begin
       for K in Data'Range loop
          Compute (Data, K);
          select
             accept Element (Result : out T) do
                Result := Data(K);
             end Element;
          or
             terminate;
          end select;
       end loop;
    end Generator;