コルーチンのサンプル

coroutine1.rkt

#lang racket
;
; original code ->
;   http://www.shido.info/lisp/scheme_cc.html
;

(require data/queue)

; coroutine
(define process-queue (make-queue))

(define (coroutine thunk)
  (enqueue! process-queue thunk))

(define (start)
  ((dequeue! process-queue)))

(define (pause)
  (let/cc k
    (coroutine (lambda () (k)))
    (start)))

; example
(coroutine (lambda ()
             (let loop ((i 0))
               (when (< i 10)
                 (display (+ 1 i))
                 (display " ")
                 (pause)
                 (loop (+ 1 i))))))

(coroutine (lambda ()
             (let loop ((i 0))
               (when (< i 10)
                 (display (integer->char (+ i 97)))
                 (display " ")
                 (pause)
                 (loop (+ 1 i))))))

(start)
(newline)