Not sure about continuations, but I'll have a stab at co-routines.

Co-routines consist of two processes, each with it's own state and executing
quasi concurrently. 

An example might be a producer and consumer process pair. Say

	P =()=> Q where they are connected via a stream.

The process Q will block until P writes something to the stream. P's writing
can be made either synchronous or asynchronous. Q is said to be re-entrant,
as it preserves it's state between invocations.

To implement this in Smalltalk you would have two processes, the scheduling
of which would be controlled by a Semaphore. See SharedQueue. Using COBOL
(what!?) you would need to separate out the state and have a goto to the
particular resume point in the code, depending on it's previously suspended
state.

Hope this helps,

Stewart 

> OK, I'll exhibit my ignorance :-).  What are continuations, 
> and what are
> they useful for?  Same questions for coroutines.
> 
> Bob Jarvis
> Compuware @ Timken
> 
> > -----Original Message-----
> > From:	Vassili Bykov [SMTP:vassili at objectpeople.com]
> > Sent:	Thursday, January 27, 2000 8:19 AM
> > To:	squeak at cs.uiuc.edu
> > Subject:	RE: Multiple Returns, was Re: Common Lisp style 
> macros in
> > Smalltalk?
> > 
> > > From: demiourgos at smalltalk.org [mailto:demiourgos at smalltalk.org]
> > > But I have wondered from time to time -- not having deep 
> process-based
> > > experience in Smalltalk (applications instead) -- how one 
> might go about
> > > implementing coroutines or continuations in the manner of 
> Scheme.  Or
> > > are these things too far out of the Smalltalk model?
> > 
> > I implemented continuations for Squeak a couple of year ago.  Nobody
> > seemed
> > particularly impressed, so even if they are not far out of 
> the Smalltalk
> > implementation, they are far out of the Smalltalk thinking.
> > 
> > --Vassili
>