[racket] Behaviour with read-only files

On Nov 17, 2011, at 10:35 AM, Matthias Felleisen wrote:

> 
> On Nov 17, 2011, at 1:13 PM, John Clements wrote:
> 
>> Minor problem: the "end" button.
> 
> Disable it until you have found the end or replace it with '1000 steps' button 
> 
> 
>> More major problem (?): world/universe code with callbacks. In this case, the only way to get the picture moving again would be to manually move the stepper to the end step. 
> 
> I don't understand this. 

Suppose you run a big-bang program that puts a dot on the screen every time you press a key.  Now suppose it runs for 1K steps and halts. The user sees that the window is frozen, but probably won't figure out that the way to un-freeze it is to go to the stepper window and advance past the end of the currently-computed steps.

> 
> 
>> For these reasons (and a general gut feeling), I think it's better to treat the stepper as a parallel process that's sending messages over to the UI side.
> 
> That's another good solution. 

I read this as you agreeing with my earlier dialog box suggestion; am I reading this correctly?

John

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