Re: Timeouts in Ada

[Robert A Duff <bobduff@shell01.TheWorld.com>]

AdaMagica <christ-usch.grein@t-online.de> writes:

>    select
>      call_1(params)
>    or
>      call_2(params)
>    or
>      delay 10
>    end select
>
> The model in Ada is a set of counters (or cash points in a
> supermarket), an every day experience: You (as a person) can only
> queue before one of them. That's why it is not allowed in the syntax.

It makes perfect sense to enqueue on multiple entries.
In fact, "select call_1 or delay..." enqueues twice (once on
the entry call, and once on the timer queue).

Regarding your analogy: There's a supermarket near me where they have
just one queue, and the person at the head of the queue takes the first
available cash point.  In a sense, they're enqueued on multiple cash
points.  ;-)  Like the multi-way call proposed (and rejected) for Ada 9X,
they only use one.

I think the reason multiple entries are not allowed is that during the
Ada 9X project, it was thought to be too hard to implement.
Or too hard to implement on existing implementations (which of course
had not been designed for that).

- Bob