.Re: A simple lisp problem.

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