#lang racket
#|
iempty, iempty?, icons, ifirst, irest, ilength, and iappend
|#

(provide ilist iempty iempty? icons ifirst irest ilength iappend)

(define-struct ilist (value))

(define iempty (make-ilist empty))

(define (iempty? an-ilist)
  (cond
    [(empty? (ilist-value an-ilist)) true]
    [else false]))

(define (ifirst an-ilist)
  (first (ilist-value an-ilist)))

(define (irest an-ilist)
  (make-ilist (rest (ilist-value an-ilist))))

(define (icons num an-ilist)
  (make-ilist (append (list num) (ilist-value an-ilist))))

(define (ilength an-ilist)
  (length (ilist-value an-ilist)))

(define (iappend ilist1 ilist2)
  (make-ilist (append (ilist-value ilist1) (ilist-value ilist2))))

;(define someilist (make-ilist (list 1 2 3)))
;(iempty? iempty)
;(iempty? someilist)
;(ifirst someilist)
;(irest someilist)
;(icons 3 someilist)
;(ilength someilist)
;(iappend someilist (make-ilist (list 1 2 3)))