Re: multiple delay alternative

["Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org>]

On 03/05/2018 02:50 PM, Mehdi Saada wrote:
> It stands to reason that
> select
>>            delay <time>;
>>            <entry call>;
>>       or
>>            delay <time>;
>>            <entry call>;
>>       or
>>            delay <time>;
>>            <entry call>;
>>       end select;

This is confusing. Because it mentions entry calls, one might think it's a timed 
entry call, but that only allows a single delay alternative. And you don't 
usually have both a delay and an entry call in the same branch. A selective 
accept can have multiple delay alternatives, but has accept statements rather 
than entry calls. Again, you don't usually have a delay and an accept in the 
same branch.

> is not allowed for the caller, or you could try and call on multiple entrees at the same time, and pick up on of them... meaningless.

In Ada, you can do

select
    Entry_1;
then abort
    Entry_2;
end select;

Need more than 2? No problem; these can be nested

select
    Entry_1;
then abort
    select
       Entry_2;
    then abort
       Entry_3;
    end select;
end select;

The semantics of this seem somewhat confusing, though. While it's possible that 
only one of the entry calls will complete, it's also possible that any number of 
them will complete, including all of them.

-- 
Jeff Carter
"All citizens will be required to change their underwear
every half hour. Underwear will be worn on the outside,
so we can check."
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