wingoquiz.scm

(define (discriminate f)
  (define first? #t)
  (define k #f)
  (define (discriminator)
    (define (return x) x)
    (let ((x
           (f (lambda (x)
                (when first?
                  (set! first? #f)
                  (set! return (call/cc (lambda (resume)
                                          (set! k resume)
                                          return))))
                x))))
      ;; ordering explicitly introduced so I can mutated return
      (return x)))
  ;; remember kids, r5rs scheme does not specify left-to-right
  ;; ordering for defines, or function application.
  (discriminator)
  (let* ((r1 (call/cc k))
         (r2 (call/cc k)))
    (eqv? r1 r2)))


(define (test1 get)
  (let ((v (make-vector 2 #f)))
    (vector-set! v 0 (get 0))
    (vector-set! v 1 (get 1))
    v))

(define (test2 get)
  (let* ((a (get 0))
         (b (get 1)))
    (vector a b)))