Hi Jos and ALL, The code is from website
http://stackoverflow.com/questions/4175626/scheme-recursion-error I modified it. It is not about homework. I am learning and evaluating Racket. I use Language: racket; memory limit: 128 MB in DrRacket. The error I get is > (test 'a '(b a c a)) . . procedure application: expected procedure, given: '(b a c a) (no arguments) I found the problem. I should use helper v not helper (v) Here is another question. In (lambda (ls), it seems ls took the value from v. How does Racket know not pass x to ls as the argument? Does it alway takes the right variable? What happens if the first lambda has 3 parameters and the 2nd lambda has 2 parameters? Also, I want code to keep all the letters that is not a. It does not work for (test 'a #(b c a b a d)). The result is '(c b). If you know how to generalize it, please let me know. Thanks a lot. On Thu, Jun 2, 2011 at 4:10 AM, Jos Koot <jos.k...@telefonica.net> wrote: > Whast you describe seems correct. > How about showing me yoyur code after deleting vector->list? > > If this is HOMEWORK, send it OFF LIST. > > What language did you use? > > Jos > > ------------------------------ > *From:* users-boun...@racket-lang.org [mailto: > users-boun...@racket-lang.org] *On Behalf Of *Yingjian Ma > *Sent:* 02 June 2011 08:45 > *To:* users@racket-lang.org > *Subject:* [racket] please help to change vector to list > > Hi ALL, > > I have this code > > (define test > (lambda (x v) > (define helper > (lambda (ls) > (cond > ((empty? ls) '()) > ((empty? (rest ls)) '()) > ((equal? (second ls) x) (cons (first ls) (helper (rest > ls)))) > (else (helper (rest ls)))))) > (helper (vector->list v)))) > > When I run it with > > (test 'a #(b a c a)) > it returns > '(b c) > > Is there a way to use the list such as (test 'a '(b a c a))? I tried to > delete vector->list from the last line of the code, but it did not work. > Why? > > Thanks a lot > >
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