Den man. 27. apr. 2020 kl. 04.36 skrev Kristina Marie <kahrend...@gmail.com
>:
> Hello,
> I am trying to use HtDF to create a function to sort a Binary Search Tree.
> I am in an intro class so this may be a simple question. I did the
> following:
>
> ;define-struct a node
> (define-struct node (left value right))
>
...
> ; Purpose: sort a binary tree
> ; Signature: node -> list
> ; Examples:
> (check-expect (bst-sort null)(list))
> (check-expect (bst-sort a-node)(list "A"))
> (check-expect (bst-sort j-node)(list "H" "I" "J"))
> (check-expect (bst-sort root)(list "A" "B" "C" "D" "E" "F" "G" "H" "I" "J"
> "K"))
>
> ;Code
> (define (bst-sort nod)
> (cond
> [(null? nod)(list)]
> [(and (null? (node-left nod)) (null?(node-right nod)))
> (list(node-value nod))]
> [else
> (string-append (bst-sort (node-left nod) (list (node-value
> nod)) (bst-sort (node-right nod))))
> ]
> )
> )
>
>
This expression
(bst-sort (node-left nod) (list (node-value nod)) (bst-sort
(node-right nod))))
is the problem. It can be reformatted to make it clearer:
(bst-sort (node-left nod)
(list (node-value nod))
(bst-sort (node-right nod))))
You are providing 3 arguments to bst-sort, but according to your signature:
; Signature: node -> list
it only takes one input.
Furthermore the `string-append` needs to be removed, since bst-sort returns
a list, not a string.
/Jens Axel
> I keep getting this test failure:
> bst-sort: expects only 1 argument, but found 3
>
> It has to due with the two last check-expects failing because of the
> highlighted line.
>
> I ran this same code with integers and removed the string from append and
> it passed. Any advice?
>
> --
> 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/e5e05ebe-87ed-4d49-8a18-d3b58bae4e38%40googlegroups.com
> <https://groups.google.com/d/msgid/racket-users/e5e05ebe-87ed-4d49-8a18-d3b58bae4e38%40googlegroups.com?utm_medium=email&utm_source=footer>
> .
>
--
--
Jens Axel Søgaard
--
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/CABefVgyyOCTLVomOhEWtOT%3DOOOdyNM%2BxcSEee4kdDctbspBDOg%40mail.gmail.com.
