[racket] struct contract violation problem

On Wed, Oct 23, 2013 at 3:31 PM, Jay McCarthy <jay.mccarthy at gmail.com>wrote:

> Here are two ideas.
>
> 1) You simply have an old use of the original net/url. When #<url> is
> printed, it uses the symbolic name and you can't really figure out
> what the underlying code came from. I would do a grep to make sure
> this is not the case.
>

Would the operative places to look be the point at which the url object is
created and then where it is used? In other words, if it is created in the
context of net/url (i.e. a module where net/url is required) and used in a
module with adaptnet/url required, it will look like a #<url> (when
printed) but not be a url? according to adaptnet/url's url-structs, and
where the object travels in between doesn't make a difference?


> 2) You are using namespaces somewhere and actually have two instances
> of the same module somewhere where a value produced by copy 1 is going
> to copy 2. This is possible with the Web server if you don't set up
> the servlet namespace properly:
>
>
> http://docs.racket-lang.org/web-server-internal/dispatch-servlets.html#(part._namespace)
>
> On Wed, Oct 23, 2013 at 4:25 PM, Erik Pearson <erik at adaptations.com>
> wrote:
> > Excuse my poor experience with contracts, this is probably an easy one.
> >
> > I'm using a copy of net/url and have a strange problem. The copied
> library
> > is working fine in general, but this problem cropped up today:
> >
> > struct:exn:fail:contract:blame url-port: contract violation
> > expected: url?
> > given: #<url>
> > in: the 1st argument of
> > (-> url? (or/c #f number?))
> > contract from:
> > /home/epearson/work/racket/github/adaptnet/url-structs.rkt
> > blaming: /home/epearson/work/racket/github/racqueb/httpc.rkt
> > at: /home/epearson/work/racket/github/adaptnet/url-structs.rkt:4.28
> >
> > The error is thrown in my usage of url-port which is being passed a
> > perfectly good url struct object. The file is requiring the copied
> > url-structs. If I play with the function that is being blamed in
> httpc.rkt
> > via the repl in dr racket, this specific error is not thrown. The call to
> > (url-port url) succeeds without throwing this contract exception.
> >
> > From my primitive understanding, I'm flummoxed: Why is a #<url> not a
> url?
> >
> > I suspected that there may have been a leftover require of net/url
> confusing
> > things, but I can't find any in my code.
> >
> > Using racket head from github 5.90.0.9--2013-10-20(d6610289/d)
> >
> > Help!
> >
> > Thanks,
> > Erik.
> >
> >
> >
> > ____________________
> >   Racket Users list:
> >   http://lists.racket-lang.org/users
> >
>
>
>
> --
> Jay McCarthy <jay at cs.byu.edu>
> Assistant Professor / Brigham Young University
> http://faculty.cs.byu.edu/~jay
>
> "The glory of God is Intelligence" - D&C 93
>



-- 
Erik Pearson
Adaptations
;; web form and function
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