cc.scm

(define (generate-one-element-at-a-time lst)
 
;; Hand the next item from a-list to "return" or an end-of-list marker
    (define (control-state return)
        (for-each
            (lambda (element)
                (call/cc ;;where after indexing one element and move to another element
                    (lambda (resume-here)
;; Grab the current continuation
                        (set! control-state resume-here)
                        (return element))))
            lst)
        (return 'you-fell-off-the-end))
 
;; This is the actual generator, producing one item from a-list at a time
    (define (generator)
        (call/cc control-state));;where generator return passing as arg to control-state
 
;; Return the generator
    generator)
 
(define generate-digit
(generate-one-element-at-a-time '(0 1 2)))