Call With Current Continuation: Coroutine

(define (coroutine routine)
  (let ((current routine)
        (status 'suspended))
    (lambda args
      (cond ((null? args) 
             (if (eq? status 'dead)
                 (error 'dead-coroutine)
                 (let ((continuation-and-value
                        (call/cc (lambda (return)
                                   (let ((returner
                                          (lambda (value)
                                            (call/cc (lambda (next)
                                                       (return (cons next value)))))))
                                     (current returner)
                                     (set! status 'dead))))))
                   (if (pair? continuation-and-value)
                       (begin (set! current (car continuation-and-value))
                              (cdr continuation-and-value))
                       continuation-and-value))))
            ((eq? (car args) 'status?) status)
            ((eq? (car args) 'dead?) (eq? status 'dead))
            ((eq? (car args) 'alive?) (not (eq? status 'dead)))
            ((eq? (car args) 'kill!) (set! status 'dead))
            (true nil)))))