如何在球拍中循環？

Question

我想循環這一個，直到nr-of-bread是2如何做到這一點？

(when (and (>= money price-of-bread) (< nr-of-bread 2)) 
     (set! nr-of-bread (+ nr-of-bread 1)) (set! money (- money price-of-bread))) 

Answer 1

實現通過一個名爲let正在使用尾遞歸的最好方法：

(let loop ((nr-of-bread 0) 
      (rest money)) 
    (if (and (>= rest price-of-bread) (< nr-of-bread 2)) 
    (loop (add1 nr-of-bread) (- rest price-of-bread)) 
    nr-of-bread))