(letrec ((spawn-thread
	  (lambda (it . args)
	    (call/cc (apply it args))))
	 
	 (main
	  (lambda (label . sequence)
	    (lambda (cc)
	      (let loop ((sequence sequence)
			 (state 0))
		(printf "IN MAIN THREAD ~A~N---" state)
		(if (< state 10)
		    (loop `(,@(cdr sequence) ,(call/cc (car sequence)))
			  (+ state 1)))))))
	 
	 (with-exit (lambda (label data)
		      (lambda (cc)
			(let loop ((cc cc) (done (lambda () #f)) (state 0))
			  (cond ((done) (cc data))
				(else
				 (printf "IN THREAD ~A TYPE: WITH-EXIT STATE: ~A~N" label state)
				 (loop (call/cc cc) done (+ state 1))))))))
	 
	 (no-exit (lambda (label data)
		    (lambda (cc)
		      (let loop ((cc cc) (state 0))
			(printf "IN THREAD ~A TYPE: NO-EXIT STATE: ~A~N" label state)
			(loop (call/cc cc) (+ state 1))))))
	 ;breaks it for some reason?
	 (no-reps (lambda (label data)
		    (lambda (cc)
		      (printf "IN THREAD ~A TYPE: NO-REPS~N" label)
		      (call/cc cc)))))
  
  (spawn-thread main 'main
		(spawn-thread with-exit 1 '())
		(spawn-thread no-exit 2 '())
		(spawn-thread with-exit 3 '())
		;(spawn-thread no-reps 4 '())) uncomment to see error
		))

;you can run this as is, and it works, entering the main thread and then subsequently yielding control to the next thread in the sequence. for some reason the no-reps thread generator breaks it though :/