[plt-scheme] DrScheme buglet?

From: Ryan Culpepper (ryanc at ccs.neu.edu)
Date: Wed Aug 29 11:17:30 EDT 2007

On Wed, 2007-08-29 at 08:52 -0500, Robby Findler wrote:
> This only happens when there are syntax errors, right? Not runtime errors?
> I think that's just a property of the way teachpacks work in the
> current world. I'm not sure it is possible to get around that.
> Roughly, what's happening underneath the hood, is that the teachpack
> is (an invisible) part of your program and, when your program is
> syntactically malformed, no part of your program is available in the
> REPL. For example, in this program:
>   (define x 1)
>   unbound-id
> You won't be able to use "x" in the REPL. But, in this one, you will:
>   (define x 1)
>   (first empty)
> I know that's not real help, but I hope it is at least explanatory.
> And maybe this will inspire someone (Matthew?) to think of a way to do
> better, I'm not sure.

Would it make sense to make that explanation part of DrScheme? That is:

When a syntax error occurs, print a message to the effect of "No
definitions executed due to syntax error" in the interactions window and
lock the interactions editor.

Or instead of locking the interactions, DrScheme could instead display
one of those yellow highlighted messages (like "definitions out of sync"
is displayed now) before every interaction. That would let students use
the interactions window to stumble around trying out syntaxes until they
find the right one.


> On 8/29/07, Todd O'Bryan <toddobryan at mac.com> wrote:
> > In v371 of DrScheme, it appears that teachpacks don't "stick."
> >
> > When you first open a DrScheme window, even though it says that a
> > teachpack is loaded, it's unavailable until you hit Run.
> >
> > That's not a big problem, but the teachpacks disappear if there's an
> > error during a Run. In other words, if students are developing a
> > function, hit run, and have an error, if they drop down to the
> > interactions window to experiment, the functions provided by the
> > teachpack are no longer available.
> >
> > The workaround is to comment out offending code in the definitions
> > window, but this is kind of a pain.
> >
> > Todd
> >
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