Goto🔗 i

3.1Loop🔗 i

(let ([x0])

(define loop(label ))

(set! x(add1 x))

(when (< x7)(goto loop))

(displayln x))

3.2Yin-Yang Puzzle🔗 i

(let ([kn(current-continuation )])

(display #\@)

(let ([kn+1(current-continuation )])

(display #\*)

(knkn+1)))

(let* ([k#f][k0(label )])

(unless k(set! kk0)(goto k))

(display #\@)

(let* ([knk][kn+1(label )])

(when (eq? knk)(set! kkn+1)(goto k))

(display #\*)

(goto kn)))

(define (k0kn)

(display #\@)

(define (kn+1k)

(display #\*)

(knk))

(kn+1kn+1))

(k0k0)

3.3Call with Current Continuation🔗 i

(define (call/cc proc)

(define (dispatcherk. v*)

(if k

(proc(curry k#f))

(apply values v*)))

(call-with-values cc dispatcher))

(define (call/cc proc)

(define v*#f)

(define l(label ))

(if v*

(apply values v*)

(proc(λ vs(set! v*vs)(goto l)))))

3.4Light-Weight Process🔗 i

(let ([lwp-queue(make-queue )])

(define (start)

(when (non-empty-queue? lwp-queue)

(goto (dequeue! lwp-queue))))

(define (lwp-enqueue!breakcontinue)

(define first?#t)

(define l(label ))

(case/eq first?

[(#t)

(set! first?#f)

(enqueue! lwp-queuel)

(break)]

[(#f)(continue)]))

(define (pause)(lwp-enqueue!startvoid ))

(define (lwpthk)(lwp-enqueue!void (λ ()(thk)(start))))

(lwp(λ ()(goto (begin0 (label )(pause)(display #\h)))))

(lwp(λ ()(goto (begin0 (label )(pause)(display #\e)))))

(lwp(λ ()(goto (begin0 (label )(pause)(display #\y)))))

(lwp(λ ()(goto (begin0 (label )(pause)(display #\!)))))

(lwp(λ ()(goto (begin0 (label )(pause)(newline )))))

(start))

3.5Ambiguous Operator🔗 i

(let ([task*'()])

(define (fail)

(if (null? task*)

(error "Amb tree exhausted")

(goto (car task*))))

(define (amb*. alt*)

(define first?#t)

(define task(label ))

(when (null? alt*)(fail))

(when first?

(set! first?#f)

(set! task*(cons tasktask*)))

(define alt(car alt*))

(set! alt*(cdr alt*))

(when (null? alt*)

(set! task*(cdr task*)))

(when (eq? altamb*)

(goto task))

(alt))

(define-syntax-rule (ambexp*... )(amb*(λ ()exp*)... ))

(let ([w-1(amb"the""that""a")]

[w-2(amb"frog""elephant""thing")]

[w-3(amb"walked""treaded""grows")]

[w-4(amb"slowly""quickly")])

(define (joins?leftright)

(equal?

(string-ref left(sub1 (string-length left)))

(string-ref right0)))

(unless (joins?w-1w-2)(amb))

(unless (joins?w-2w-3)(amb))

(unless (joins?w-3w-4)(amb))

(list w-1w-2w-3w-4)))