Re: [racket-users] Question on test failures sorting a BTS

[Jon Zeppieri]

In addition to what Jens said, you should probably give a definition
of a BST at the top, and give some thought to the question of why a
BST is not simply the same thing as a node.

- Jon

On Sun, Apr 26, 2020 at 10:36 PM Kristina Marie  wrote:
>
> 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))
> ;BTS leafs
> (define a-node(make-node null "A" null))
> (define b-node (make-node null "B" null))
> (define e-node (make-node null "E" null))
> (define h-node (make-node null "H" null))
> (define i-node (make-node null "I" null))
>
> ;BTS internal
> (define c-node (make-node a-node "C" b-node))
> (define j-node (make-node h-node "J" i-node))
> (define k-node (make-node j-node "K" null))
> (define f-node (make-node e-node "F" null))
> (define g-node (make-node f-node "G" k-node))
>
> ;Root
> (define root (make-node c-node "D" g-node))
>
> ; 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
>]
>)
>  )
>
> 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?
>
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Re: [racket-users] Question on test failures sorting a BTS

[Jens Axel Søgaard]

Den man. 27. apr. 2020 kl. 04.36 skrev Kristina Marie :

> 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
> 
> .
>


-- 
-- 
Jens Axel Søgaard

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[racket-users] Question on test failures sorting a BTS

[Kristina Marie]

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))
;BTS leafs
(define a-node(make-node null "A" null))
(define b-node (make-node null "B" null))
(define e-node (make-node null "E" null))
(define h-node (make-node null "H" null))
(define i-node (make-node null "I" null))

;BTS internal
(define c-node (make-node a-node "C" b-node))
(define j-node (make-node h-node "J" i-node))
(define k-node (make-node j-node "K" null))
(define f-node (make-node e-node "F" null))
(define g-node (make-node f-node "G" k-node))

;Root
(define root (make-node c-node "D" g-node))

; 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
   ]
   )
 )

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?

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