Some common operation on Scheme List structure

listop.ss

(define (delete-n list n)
  (if (= n 0)
      (cdr list)
      (cons (car list) (delete-n (cdr list) (- n 1)))))

(define (insert-n list item n)
  (if (= n 0)
      (cons item list)
      (cons (car list) (insert-n (cdr list) item (- n 1)))))

(define (list-nth list n)
  (if (= n 0)
      (car list)
      (list-nth (cdr list) (- n 1))))

(define (replace-nth list n item)
  (if (= n 0)
      (cons item (cdr list))
      (cons (car list) (replace-nth (cdr list) (- n 1) item))))

(define (swap-list-item list m n)
  (let
    ((a (list-nth list m))
     (b (list-nth list n)))
    (replace-nth
      (replace-nth list m b) n a)))

(swap-list-item (list 1 2 3 4 5 6) 2 4)

(replace-nth (list 3 2 9 2) 2 8)
(delete-n (list 1 2 3 4 5) 2)
(insert-n (list 1 2 3 4 5) 10 2)
(list-nth (list 1 2 3 4 5) 3)