2011/1/21 Insik Cho <imin...@gmail.com>: > hi guys, > > I have used 'call/input-url' function frequently, whose definition is: > > (call/input-url URL connect handle) → any > URL : url? > connect : (url? . -> . input-port?) > handle : (input-port? . -> . any) > > I coded like: > > (define a-url (string->url "http://www.google.com";)) > (call/input-url a-url get-pure-port (lambda (p) (display (read-bytes 1024 > p)))) > > Tired to type 'lambda' function, I extracted it like: > > (define a-url (string->url "http://www.google.com";)) > (define (read-1024 p) (display (read-bytes 1024 p))) > (call/input-url a-url get-pure-port (read-1024 p))
You are calling "read-1024" with the argument "p" which appears to be free in this program. You don't want to pass call/input-url the result of read-1024, you want to call it with read-1024 itself: (call/input-url a-url get-pure-port read-1024) > > But, it generates errors. > > What's wrong? > The question is: what 'handle' means? 'handle' has no special meaning in Racket. This library just uses that name. > Is it like a callback function in C? You could imagine that it is a "callback" from call/input-url to your code to do something to the port before it closes it. Jay > > Thanks in advance. > > - Joe > > > > _________________________________________________ > For list-related administrative tasks: > http://lists.racket-lang.org/listinfo/dev -- Jay McCarthy <j...@cs.byu.edu> Assistant Professor / Brigham Young University http://faculty.cs.byu.edu/~jay "The glory of God is Intelligence" - D&C 93 _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/dev
