I have what may be a silly question about continuations.  First, some  
background.

I'm about to give a lecture on Continuations.  I'm trying to model  
what the "functional people" do, just to show off the flexibility of  
Smalltalk.  I'm working in the Seaside one-click image, because,  
having introduced continuations, I want to talk about the way that  
they are used in Seaside to implement natural control flow.  So, I'm  
not trying to solve any particular programming problem

Here is a little example that I wrote to illustrate a continuations.

SeasideDemo >> countUpTo: initialInterruptValue
	"demonstrate resumable continuations"
	| interruptValue |
	interruptValue := initialInterruptValue.
	1 to: 1000
		do: [:i |
			Transcript show: 'i = '.
			Transcript show: i.
			Transcript cr.
			i = interruptValue
				ifTrue: [interruptValue := Continuation
						currentDo: [:cc | ^ cc]]]



If I execute

	d := SeasideDemo new.
	c := d countUpTo: 7

in a workspace, I get

i = 1
i = 2
i = 3
i = 4
i = 5
i = 6
i = 7

in the Transcript, as you would expect.  Then the method returns, with  
a continuation, which I name c

I can then resume that continuation:

	c value: 12

and the count in the transcript goes

i = 8
i = 9
i = 10
i = 11
i = 12

as I would expect.  However, if I "doit" c value:12 a second time, the  
count resumes from 13, not from 8.  This surprised me.

Strangely, if instead of assigning the result of d countUpTo:7 to c, I  
just inspect it, and doIt

	self value: 12

in the inspector, then the count continues from 8 to 12.  I can doIt  
multiple times, and each time the count goes from 8 to 12.
However, what is strange is that I get a new inspector on a new  
continuation each time I doIt.  I can only infer that the initial  
"inspect It" has somehow been captured as part of the continuation.

I'm also confused to find that the result of

	c2 := c value: 15

is not a new continuation, that will count up from 15 but ... nil.

Are my expectations wrong?  Are there bugs in the Seaside  
implementation of Continuations?  Or what?

	Andrew



____________________________
Prof. Andrew P. Black
Department of Computer Science
Portland State University
Oregon, USA

http://www.cs.pdx.edu/~black
Telephone: +1 503 725 2411