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From: "B. Pym" <No_spamming@noWhere_7073.org>
Newsgroups: comp.lang.lisp
Subject: .Re: A simple lisp problem.
Date: Sat, 15 Jun 2024 03:45:39 -0000 (UTC)
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Frank Schwieterman wrote:

> >I am Lisp beginner and I am doing a simple execise on lisp. I was asked
> >to write a lisp program , by using either recursion or do, to return
> >true if the difference between each successive pair of the them is 1.
> >
> >ie:
> >
> >>(difference '(2 1))
> >T
> >>(difference'(3 4 5 6 5 4))
> >T
> >>(differnce '(3 4 5 3))
> >NIL
 ....
> 
> (defun difference (param)
>      (if (> (length param) 1)
>         (if (<= (abs (- (first param) (first (rest param)))) 1 )
>            (difference (rest param))
>            nil
>            )
>         T
>         )
>      )

Gauche Scheme

(define (diff1? xs)
  (every
    (lambda (a b) (= 1 (abs (- a b))))
    xs
    (cdr xs)))

(diff1? '(2 3 4 3 4 5 6 7 8 9 8))
  ===>
#t
(diff1? '(2 3 4 3 4 5 6 7 8 9 8 0))
  ===>
#f