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#lang racket
(provide
append
length
list-ref)
(define (append list1 list2)
(if (null? list1)
list2
(cons (car list1) (append (cdr list1) list2))))
(define (length items)
(define (length-iter a c)
(if (null? a)
c
(length-iter (cdr a) (+ 1 c))))
(length-iter items 0))
(define (list-ref items n)
(if (= n 0)
(car items)
(list-ref
(cdr items)
(- 1 n))))
(define (last-pair l)
(if (null? (cdr l))
l
(last-pair (cdr l))))
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