From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID,XPRIO
	autolearn=no autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,cbb4573e858c2040,start
X-Google-Attributes: gid103376,public
From: "nootah" <nootah@ihug.co.nz>
Subject: Newbie: Clarification of non-determinsitcis selection in Ada
 rendevous Mechanism
Date: 2000/05/17
Message-ID: <8fstnl$dd$1@news.ihug.co.nz>#1/1
X-Deja-AN: 624332436
X-Priority: 3
X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2615.200
Organization: The Internet Group Ltd
X-MSMail-Priority: Normal
Newsgroups: comp.lang.ada
Date: 2000-05-17T00:00:00+00:00
List-Id: <comp.lang.ada>

Hi people,

Currently studying a course where Ada is referred to but not taught and have
a brief section on Active Objects using the Ada rendevous mechanism as an
example.

Question is: if the selection of action from a select clause is
non-deterministic, then does the active object pause at the select statement
or does it elect one of the processes to wait for - the altter is what I
have been told. My problem with this - if multiple guard conditions are
simultaneously true, and one is selected prior to any call, then what occurs
when one of the client processes calls another guarded func.

e.g. where a=5

    select
        when a>0 =>
            accept(FirstFunc)
        when a<10 =>
            accept(SecondFunc)
        end select
    end select

If object halts at select and waits for request from client
    what happens if func called and guard condition not fulfilled ? -
presumably client blocks until condition met and task can respond - queues
the request and blocks client

On the other hand, if object elects FirstFunc, but client SecondFunc is
first call received - what happens ? presumably .. I have no idea!

Any help gratefully  appeciated .
Cheers
Andy