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#lang racket
;;; Exercise 01
(define (list-len a)
(if (null? a)
0
(add1 (list-len (cdr a)))))
;;; Exercise 02
(define (list-contains lst elem)
(cond [(null? lst) #f]
[(= (car lst) elem) #t]
[else (list-contains (cdr lst) elem)]))
;;; Exercise 03
(define (list-insert lst elem ind)
(if (= ind 0)
(list* elem lst)
(list* (car lst) (list-insert (cdr lst) elem (sub1 ind)))))
;;; Exercise 04
(define (list-min lst)
(define (calc-iter lst minel)
(cond [(null? lst) minel]
[(< (car lst) minel) (calc-iter (cdr lst) (car lst))]
[else (calc-iter (cdr lst) minel)]))
(calc-iter lst (car lst)))
;;; Exercise 05
(define (remove-first lst elem)
(if (= (car lst) elem)
(cdr lst)
(if (null? (cdr lst))
lst
(list* (car lst) (remove-first (cdr lst) elem)))))
;;; Exercise 06
(define (remove-elem lst elem)
(if (null? lst)
lst
(if (= (car lst) elem)
(remove-elem (cdr lst) elem)
(list* (car lst) (remove-elem (cdr lst) elem)))))
;;; Exercise 07
(define (list-concat lst1 lst2)
(if (null? lst1)
lst2
(if (null? (cdr lst1))
(list* (car lst1) lst2)
(list* (car lst1) (list-concat (cdr lst1) lst2)))))
;;; Exercise 08
(define (list-rev lst)
(define (calc-iter toret lst)
(if (null? lst)
toret
(calc-iter (list-insert toret (car lst) 0) (cdr lst))))
(calc-iter '() lst))
;;; Exercise 09
(define (remove-duplicates subxs xs)
(if (= (car xs) subxs)
(list* (car xs) (remove-elem (cdr xs) subxs))
(list* (car xs) (remove-duplicates subxs (cdr xs)))))
;;; Exercise 10
(define (sublist-between start end xs)
(cond [(> start 0) (sublist-between (sub1 start) (sub1 end) (cdr xs))]
[(> end 1) (list* (car xs) (sublist-between 0 (sub1 end) (cdr xs)))]
[else (list (car xs))]))
;;; Exercise 11
(define (count-occurrences subxs xs)
(define (calc-iter occs lst)
(if (null? lst)
occs
(calc-iter (if (= (car lst) subxs) (add1 occs) occs)
(cdr lst))))
(calc-iter 0 xs))
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