使用Lisp递归检查连续数字 [英] Check consecutive numbers recursively using Lisp

问题描述

我正在尝试编写一个递归函数，以检查列表中的元素是否连续增加.

I'm trying to write a recursive function to check if the elements of a list are increasing consecutively.

(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)应该返回1.如何正确编写此函数?

(test consecutive) should return 1. How can I write this function correctly?

推荐答案

要检查序列中的数字是否连续 ，即 随着步骤1的增加，您需要这样做:

To check that the numbers in the sequence are consecutive, i.e., increasing with step 1, you need this:

(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

NB .数字不能很好地代替布尔值.

NB. Numbers are a poor substitute for booleans.

PS .我想知道这是否与如何检查列表中的所有数字是否都在稳定增加? ...

PS. I wonder if this is related to How to check if all numbers in a list are steadily increasing?...

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