[plt-scheme] The contract

Hi,

  I'm fresh to contracts. Here is my problem:

I just want to pass the contracts check on the following definition:

 (define test (lambda (url)
                 (post-impure-port url data rhead)))

(provide/contract (test (-> url? input-port?)))

(call/input-url (string->url "https://210.77.16.29/php/user_login.php") test
display-pure-port)

or even more simplified:

(call/input-url (string->url "https://210.77.16.29/php/user_login.php")
                   (lambda (url)
                      (post-impure-port url data rhead)))
                  display-pure-port)

Every time, I get:
  (case->
    (->
     url?
     (case->
       (-> url? input-port?)
       (-> url? (listof string?) input-port?))
     (-> input-port? any)
     any)
    (->
     url?
     (case->
       (-> url? input-port?)
       (-> url? (listof string?) input-port?))
     (-> input-port? any)
     (listof string?)
     any))
on call/input-url; expected a procedure that accepts 2 arguments, given:
#<procedure:test>

If I change the definition to
(call/input-url (string->url "https://210.77.16.29/php/user_login.php")
                  (lambda (url rhead)
                    (post-impure-port url data rhead)
                    )
                  display-pure-port
                  )
. . ssl-url.scm:40:4: /home/yug/ssl-url.scm:40:4: top-level broke the
contract
  (case->
    (->
     url?
     (case->
       (-> url? input-port?)
       (-> url? (listof string?) input-port?))
     (-> input-port? any)
     any)
    (->
     url?
     (case->
       (-> url? input-port?)
       (-> url? (listof string?) input-port?))
     (-> input-port? any)
     (listof string?)
     any))
on call/input-url; expected a procedure that accepts 1 arguments, given:
#<procedure>
>

How can I define my function?

Thanks

-- 
Gang
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