[racket] Apparent bug in Windows environment - “Submit occurs multiple times”

From: Jay McCarthy (jay.mccarthy at gmail.com)
Date: Thu Sep 19 09:35:22 EDT 2013

Are you using the same browser in both cases?

Browsers behave differently with regard to the way they handle Submit
buttons sometimes and I think IE is the main offender.

Furthermore, extract-binding/single is very brittle to use because it
assumes that the binding appears only once (that's what the "single"
is about) but queries are allowed to contain the same binding any
number of times. This is one of the reasons why it is better to use
bindings-assq and why extract-binding/single is deprecated.


On Wed, Sep 18, 2013 at 11:07 AM, Simon Dehne <scdehne at googlemail.com> wrote:
>  I have a (for now) identical web application running on a Linux server as
> well as on a Windows server. It is running flawlessly on the Linux
> environment, however I have strange problems on the Windows platform. When I
> access the web application, I log in to the system, and am confronted with a
> Navbar with multiple buttons.
> Whenever I click one of the buttons, Racket crashes with the following
> error:
> Servlet (@
> /;((%22k%22%20.%20%22(1%2015%209487431)%22))?Submit=newcontent66&AdminProjectNavigation=2&Submit=Users&projectnavigation=2)
> exception: extract-binding/single: 'submit occurs multiple times in
> '((submit . "newcontent66") (adminprojectnavigation . "2") (submit .
> "Users") (projectnavigation . "2"))
> The code this is referring to is the following: http://pastebin.com/cYPLcvKx
> Irrelevant parts are left out. As I said, the exact same code produces no
> problems whatsoever when the application is accessed on the Linux server.
> But since we have a new project coming up, we are in need of a different
> server, which happens to be in a Windows environment. Since this is the only
> difference between the two instances of the application, I am led to believe
> this is the problem. Can anyone maybe share some insight or knows what is
> going on there?
> Best regards,
> Simon
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Jay McCarthy <jay at cs.byu.edu>
Assistant Professor / Brigham Young University

"The glory of God is Intelligence" - D&C 93

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