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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: multiple delay alternative
Date: Mon, 05 Mar 2018 23:28:03 +0000
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Date: 2018-03-05T23:28:03+00:00
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Mehdi Saada <00120260a@gmail.com> writes:

> In https://perso.telecom-paristech.fr/pautet/Ada95/chap28.htm, Ada
> tutorial's paragraph on the delayed rendezvous, it says the general
> form of this construct is:
> select 
>          delay <time>;
>          <entry call>;
>     or 
>          delay <time>;
>          <entry call>;
>     or
>          delay <time>;
>          <entry call>;
>     end select;
>
> But in the RM timed entry calls are featured like this:
> timed_entry_call ::= 
>   select
>    entry_call_alternative
>   or
>    delay_alternative
>   end select;
>
> What should I understand ?

The text in the tutorial is wrong, because the text immediately above it

    "Bill is not quite as hungry for his second meal so he is willing to
    wait for a short period at the restaurant, but if he is not served
    within one tenth of an hour, he will go to the Burger Boy for
    lunch. The single statement in lines 35 through 40 replaces the
    single statement in the previous program. In Ada terms, the task
    named Bills_Day will wait .1 hour for the Restaurant task to reach
    its entry point, after which it will call the entry point of
    Burger_Boy and wait no matter how long it takes to be served there."

shows that it's discussing entry *calls* and, as you note, there can
only be one delay alternative.

The sample code([1], from the "The Delayed Entrypoint" section, clearly
shows this.

[1] https://perso.telecom-paristech.fr/pautet/Ada95/e_c28_p3.ada