Philippe Lorin  <palpalpalpal@gmail.com> wrote:
+---------------
| Pascal Costanza wrote:
| > What do you actually want to express?
| 
| It's a kind of cooperative multitasking.
| I need three things: CSTART, CSTEP and YIELD.
+---------------

CMUCL's "multiprocessing" (green threads, really) can easily do this
[given some trivial wrappers], as can SBCL and several other Common
Lisps with threads. In the case of CMUCL, I think this [untested]
does approximately what you asked for:

    (defmacro cstart (&body body)
      `(mp:make-process (lambda () (yield) ,@body)))

    (defun cstep (c)
      (mp-enable-process c))

    (defun yield ()
      (mp-disable-process mp:*current-process*))


-Rob

-----
Rob Warnock			<rpw3@rpw3.org>
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