;; CMSC 331 Fall 2011 hw5.ss, YOUR NAME, YOUR_ID@UMBC.EDU

(define (PASS . ARGS)
  ;; This is a a dummy function that takes any number of arguments and
  ;; always returns null.  You should replace calls to it with your
  ;; own scheme code.
  null)

;; problem four: chop and unchop

(define (chop l)
  ;; chop takes a proper list l with at least one element and returns
  ;; one like it with the last element removed.
  ;; Examples: (chop '(1 2))=>(1), (chop '(1))=>()
  (PASS))

(define (unchop l x)
  ;; ADD AN APPROPRIATE COMMENT
  (PASS))

;; problem five: shift-right and shift-left

(define (shift-right l)
  ;; ADD AN APPROPRIATE COMMENT
  (PASS))

(define (shift-left l)
  ;; ADD AN APPROPRIATE COMMENT
  (PASS))

;; problem six: zipper?, zip and unzip

(define (zipper? l)
  ;; ADD AN APPROPRIATE COMMENT
  (PASS))

(define (zip l1 l2)
  ;; ADD AN APPROPRIATE COMMENT
  (PASS))

(define (unzip l) 
  ;; ADD AN APPROPRIATE COMMENT
  (PASS))