> >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

Using "every":

(define (diff1 xs)
(or (null? xs)
(every (compose ($ = 1 $) abs -) xs (cdr xs))))

Using recursion:

(define (diff1 xs)
(if (or (null? xs) (null? (cdr xs)))
#t
(if (= 1 (abs (- (car xs) (cadr xs))))
(diff1 (cdr xs))
#f)))