Generators in terms of call/cc

generator.scm

(define (generator p)
  (set! gc #f) ; Continuation in generator
  (lambda ()
    (call/cc (lambda (return)
               (if gc
                   (gc #f)
                   (p (lambda (value)
                        (call/cc (lambda (cgc)
                                   (set! gc cgc)
                                   (return value))))))))))

(define g
  (generator (lambda (yield)
               (define (loop i)
                 (yield i)
                 (loop (+ i 1)))
               (loop 0))))

(print (g))
(print (g))
(print (g))
(print (g))