After studying chapter 14 of HtDP, I decided to try putting strings into a
BST. The code below works with a few strings. I have a file with 22064
strings --- one per line. Up until 1471 words, it works. With 1472 it
yields a contract violation.
> (length (read-words))
22064
> (create-bst-word-from-list (take (read-words) 1471))
#<node>
> (create-bst-word-from-list (take (read-words) 1472))
node-word: contract violation
expected: node?
given: #<void>
context...:
/home/dbastos/public_html/rkt/functions.rkt:974:0: create-bst-word
/home/dbastos/public_html/rkt/functions.rkt:987:0:
create-bst-word-from-list
/home/dbastos/public_html/rkt/functions.rkt:987:0:
create-bst-word-from-list
/home/dbastos/public_html/rkt/functions.rkt:987:0:
create-bst-word-from-list
/home/dbastos/public_html/rkt/functions.rkt:987:0:
create-bst-word-from-list
/home/dbastos/public_html/rkt/functions.rkt:987:0:
create-bst-word-from-list
/home/dbastos/public_html/rkt/functions.rkt:987:0:
create-bst-word-from-list
/home/dbastos/public_html/rkt/functions.rkt:987:0:
create-bst-word-from-list
/home/dbastos/public_html/rkt/functions.rkt:987:0:
create-bst-word-from-list
/home/dbastos/public_html/rkt/functions.rkt:987:0:
create-bst-word-from-list
/home/dbastos/public_html/rkt/functions.rkt:987:0:
create-bst-word-from-list
/home/dbastos/public_html/rkt/functions.rkt:987:0:
create-bst-word-from-list
/home/dbastos/public_html/rkt/functions.rkt:987:0:
create-bst-word-from-list
/home/dbastos/public_html/rkt/functions.rkt:987:0:
create-bst-word-from-list
/home/dbastos/public_html/rkt/functions.rkt:987:0:
create-bst-word-from-list...
>
It seems node-word says I gave it a #<void>. Perhaps my list of words
contains a #<void>, but when I search for it, I do not find it.
> (define ls (read-words))
> (length ls)
22064
> (length (filter string? ls))
22064
> (filter void? ls)
()
So I'm perplexed.
(define-struct node (word left right))
(define (create-bst-word bst str)
(cond
((false? bst)
(make-node str false false))
((string<? str (node-word bst)) ;; insert at the left
(make-node (node-word bst)
(create-bst-word (node-left bst) str)
(node-right bst)))
((string>? str (node-word bst)) ;; insert at the right
(make-node (node-word bst)
(node-left bst)
(create-bst-word (node-right bst) str)))))
(define (create-bst-word-from-list ls)
(cond
((empty? ls) false)
(else
(create-bst-word (create-bst-word-from-list (rest ls)) (first ls)))))
(define (read-lines in)
(let* ((ln (read-line in)))
(cond
((eof-object? ln) empty)
(else (cons ln (read-lines in))))))
(define (read-words)
(call-with-input-file "words" read-lines))
Thank you in advance for any information.
____________________
Racket Users list:
http://lists.racket-lang.org/users
