[plt-scheme] PLT's debugger philosophy

From: Gregory Cooper (greg at cs.brown.edu)
Date: Tue Feb 12 15:08:51 EST 2008

> > which incurs some overhead.)  The other differences are primarily in
> > the user interface.
> Do you mean that the debugger is just missing an input field where
> the user would be able to type an expression for the runtime to
> evaluate in the context of the environment where the debugger has
> paused?

Well, it's also missing the code to perform that evaluation.  ;-)  I
haven't really investigated how hard that would be to write, but the
environment is available, so it shouldn't require any new
infrastructure in the debugger.

Currently, when execution is paused, you should be able to mouse over
variables to see their values, and to right-click (or equivalent) to
set them.  (I've noticed that this feature sometimes breaks, though.
I haven't had time to look into it deeply, but I suspect that some
macros or tools aren't assigning syntax source-location information
quite right.)


> That struck me as a feature that Grant listed (when he said "at which
> point you've got access to that stack frame at the location of the
> error at which point you can evaluate expressions") that I do not
> immediately see when reaching a breakpoint I set after using the
> Debug button.
> But I am not a PLT Scheme expert, so perhaps there is some way to get
> this effect via the Debug button that I am not seeing.
> -Felix
> p.s. Just so I do not step on anyone's toes: I am not complaining
> about anything; PLT Scheme is great; "I'm not worthy"; etc.

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