Re: searching an explanation: call/cc and 'do' strangeness

[Per Bothner <bothner@cygnus.com>]

Most likely I'm confused because I haven't really studying the messages,
but some of the claims I've seem incorrect:

>                              You can't pass the current continuation
> into scopeWalkDemo as a parameter, since the binding would be
> captured.  Maybe passing it in a variable would be helpful:

Note that call/cc makes a copy of the *control stack*.  It does *not* copy
the value stack.  The saved continuation does "capture" the variable
bindings, but it does not save, restore or do anything to the *values*
of bindings.

So something like this should work:

(let
  ((saved-continuation ...)
   (suspend (lambda (value)
             ;; swap current continuation and saved-continuation
             (call/cc (lambda (k)
	               (let ((ksaved saved-continuation))
			    (set! saved-continuation k)
			    (ksaved value))))))
   (routine1 (lambda () ... (suspend x) ...))
   (routine2 (lambda () ... (suspend y) ...)))
  (routine1))

Admittedly, this glosses over some of the difficult parts,
such as how saved-continuation is initialized (to run routine2).

What am I missing?

	--Per Bothner
Cygnus Solutions     bothner@cygnus.com     http://www.cygnus.com/~bothner