Path: news.cs.au.dk!not-for-mail
From: Flemming Gram Christensen <gram@mjolner.dk>
Newsgroups: comp.lang.beta
Subject: Re: More newbie: suspend
Date: 02 Jun 2000 11:54:33 +0200
Organization: University of Aarhus, Department of Computer Science (DAIMI)
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Atle <trollet@skynet.be> writes:

> 
> Activity:
> 	(#
> 		do cycle
> 		(#
> 		do
> 			GetOrder;	suspend;
> 			ProcessOrder;	suspend;
> 			DeliverOrder;	suspend;
> 		#)
> 	#)
> 
> Now, the document speaks about A and B being instances of this, and invoked as
> 
> cycle(#do A; .... B; .... #)
> 
> I am i n deep s<<<goo unless the sequence of events will be:
> 
> A.Getorder
> B.Getorder
> A.ProcessOrder
> B.ProcessOrder
> A.DeliverOrder
> B.DeliverOder
> A.Getorder


Yes that will be the order. I suppose A and B are declared as
A:@|Activity;

The suspend in A will continue execution at the first '...'s in the
last cycle(# .. #);

> 
> ... and so on! Eh <shut eyes> is this right (Y/N)?
> 
> Next: suspend.
> 
> Unfortunately, I know suspend in the form suspend X, where X is a variable, from Icon.

Can anyone explain the difference between the Icon suspend and the BETA?

> 
> When a generator (coroutine) suspends, will there be a legal value in the exit variable, will it be updated on each invokation?

The exit variable is not a special variable, it is a normal attribute of the object (or component).
Note you are not restricted to simple variables in the exit parts. You can write general expressions:

p:
(#  a,b,c:@integer;
enter (a,b,c)
do ...
exit (a+c,(# d:@integer; do a+b->d; d*3->d exit d#), (a,b)->max)
#);

But this is not very used.

> 
> Is there an easy-to-follow declarative program that uses coroutines as generators, so I can get this straightened out in my
> (somewhat confused) head?

Look into
beta/demo/basiclib/systemenv/. There are demos there. eg. pipe.bet or masterSlave.
buffer.bet is probably the easiest.

/Flemming Gram Christensen

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