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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Newsgroups: comp.lang.ada
Subject: Re: confusion about message passing between the tasks
Date: Sun, 26 Oct 2014 18:27:04 -0400
Organization: The World Public Access UNIX, Brookline, MA
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Date: 2014-10-26T18:27:04-04:00
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Jeffrey Carter <spam.jrcarter.not@spam.not.acm.org> writes:

> On 10/26/2014 01:31 PM, Robert A Duff wrote:
>> 
>> ...but the other way around isn't true.  Here's Tucker's example that
>> convinced me that some sort of "pragma Passive(Buffer_Task);" wasn't
>> going to cut it.  Write a PO a that is in one of two states,
>> "accepting calls to Entry_1" and "accepting calls to Entry_2",
>> never in both states at the same time, and never in neither state
>> (as observed by callers).  Pretty easy.  With rendezvous, not so
>> much.
>
> That seems pretty straightforward, whether with a PO or a passive task. Is there
> some complication I'm missing?

Maybe.  Here's my PO code:

    type State_Enum is (Accepting_Entry_1, Accepting_Entry_2);

    protected P is
        entry Entry_1;
        entry Entry_2;
    private
        State: State_Enum := Accepting_Entry_1;
    end P;

    protected body P is

        entry body Entry_1 when State = Accepting_Entry_1 do
            ...
            if ...
                State := Accepting_Entry_2;
        end Entry_1;

        entry body Entry_2 when State = Accepting_Entry_2 do
            ...
            if ...
                State := Accepting_Entry_1;
        end Entry_2;

    end P;

Can you show equivalent code using "accept"?

- Bob