Another wingo co-routine

gistfile1.scm

(define (call-with-yield proc)
  (let ((tag (make-prompt-tag)))
    (define (handler k . args)
      (define (resume . args)
        (call-with-prompt tag
                          (lambda () (apply k args))
                          handler))
      (apply values resume args))

    (call-with-prompt
     tag
     (lambda ()
       (let ((yield (lambda args
                      (apply abort-to-prompt tag args))))
         (proc yield)))
     handler)))

(define-syntax with-yield
  (syntax-rules ()
    ((_ yield exp exp* ...)
     (call-with-yield
      (lambda (yield) exp exp* ...)))))

(define (generate traverse collection)
  (with-yield yield
    (traverse yield collection)))

> (generate for-each '(three blind mice))
$1 = #<procedure resume args>
$2 = three
> ($1)
$3 = #<procedure resume args>
$4 = blind
> ($3)
$5 = #<procedure resume args>
$6 = mice
> ($1)
$7 = #<procedure resume args>
$8 = blind
> ($5)
>