[racket] export/import problem, and how to debug

On Aug 3, 2010, at 3:46 PM, Shriram Krishnamurthi wrote:

> Interesting -- thanks!
> 
> I just tracked down the source of universe.rkt, and find that it does
> something similar -- except with better error messages:
> 
>> on-tick
> on-tick: used out of context
> 
> vs.
> 
>> except-in
> . except-in: illegal use of syntax in: except-in
> 
> -----
> 
> Matthias, is it intentional that you are using this mechanism?


You mean that I create my own error messages? Yes, this 
is intentional and it contained a subtle bug that a joint 
session with Matthew and Robby in Edinburgh eliminated. (Having 
an apartment for three paid of.)


> Is this how we can/should extend universe with our new features?

If you add something to universe, I'd expect very much that 
you live up to the same level of error messages and that 
you tell me beforehand. I have a serious problem to eliminate 
to get the stepper to work on this code and any addition of a 
keyword may make this more difficult (or not). 

-- Matthias