Creating examples will show you what you need to do. Check the examples
below if I understood your intention.
; unique-right
; List<Any> -> List<Any>
; returns a list which has only the right most occurrences of the elements
of lst
(check-expect (unique-right '()) '())
(check-expect (unique-right (list "a")) (list "a"))
(check-expect (unique-right (list "a" "b" "a")) (list "b" "a"))
(check-expect (unique-right (list "a" "b" "a" "c" "d" "c")) (list "b" "a"
"d" "c"))
(define (unique-right lst)
(cond
[(empty? lst) '()]
[else (if (mymember? (first lst) (rest lst))
(unique-right (rest lst))
(cons (first lst) (unique-right (rest lst))))]))
; mymember
; Any List<Any> -> Boolean
; is elt in list
(check-expect (mymember? "a" '()) #false)
(check-expect (mymember? "a" (list "a")) #true)
(check-expect (mymember? "c" (list "a" "b" "a")) #false)
(define (mymember? elt lst)
(cond
[(empty? lst) #false]
[else (or (equal? elt (first lst))
(mymember? elt (rest lst)))]))
On Friday, July 24, 2020 at 11:43:48 AM UTC+8, JJ C wrote:
>
> I am in a course where I have to use beginning student with list
> abbreviation in Racket to do assignments.
> Below is my code for unique-right, which is supposed to return a list
> which has only the right most occurrences of the elements of list.
> The restriction in doing the asisngment is that I cannot use any of the
> built-in functions such as append or member.
> I'd need to re name a function and define it as I was doing below. For
> example, in the place where I need to use member? I renamed it as mymember.
> Now what I am trying to do is define the helper function mymember. I know
> that that bold part is incorrect but I have no idea at the moment how to
> make the code correct.
>
>
>
>
> ; unique-right
> ; List<Any> -> List<Any>
> ; returns a list which has only the right most occurrences of the elements
> of lst
>
> (define (unique-right lst)
> (cond
> [(empty? lst) lst]
> [else (if (mymember? (first lst) (rest lst)) (unique-right (rest lst))
> (cons (first lst) (unique-right (rest lst))))]))
>
>
>
> *; mymember*
> *; List<Any> -> List<Any>*
> *; returns a list that has all of the elements of lst plus a non-occurring
> elt*
>
> *(define (mymember elt lst)*
> * (cond*
> * [(empty? lst) lst]*
> * [else (if (equal? elt (first lst))*
> * lst*
> * (cons (mymember elt (rest lst)))]))*
>
>
>
>
>
--
You received this message because you are subscribed to the Google Groups
"Racket Users" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to racket-users+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/racket-users/1e2421da-4c5c-4d31-9d7d-8b2db15b9383o%40googlegroups.com.
