scheme - 重复代码次数

Question

我正在学习 Racket，我需要一些帮助。如何只运行此函数 4 次而不是无限运行它？

(define loop
  (λ ()
    (define delay (random 5))
    (digital-write led1 HIGH)
    (sleep delay)
    (displayln delay)
    (digital-write led1 LOW)
    (sleep delay)
    (loop)))

Answer 1

一个简单的方法是使用for。

(define (do-it-once)
  (define delay (random 5))
  (digital-write led1 HIGH)
  (sleep delay)
  (displayln delay)
  (digital-write led1 LOW)
  (sleep delay))

(for ([n 4]) 
  (do-it-once))