recursion - 使用 Lisp 递归检查连续数字

Question

我正在尝试编写一个递归函数来检查列表的元素是否连续增加。

(defun test (lst)   
 (if (null lst)
   1
   (if (= (car lst) (1- (test (cdr lst))))
    1     
    0)))

(setq consecutive '(1 2 3 4))
(setq non-consecutive '(2 5 3 6))

结果是:

CL-USER> (test non-consecutive)
0
CL-USER> (test consecutive)
0

(test consecutive) 应返回 1。如何正确编写此函数？

Answer 1

检查序列中的数字是否连续，即随着第 1 步的增加，你需要这个:

(defun list-consecutive-p (list)
  (or (null (cdr list))
      (and (= 1 (- (second list) (first list)))
           (list-consecutive-p (rest list)))))

然后

(list-consecutive-p '(1 2 3 4))
==> T
(list-consecutive-p '(1 4))
==> NIL
(list-consecutive-p '(4 1))
==> NIL

注意。数字不能很好地替代 bool 值。

附言。我想知道这是否与 How to check if all numbers in a list are steadily increasing? 有关...