[Grace-core] Undefined Variables

[Michael Homer]

On Thu, Feb 26, 2015 at 8:37 AM, Andrew P. Black <black at cs.pdx.edu> wrote:
> I woke up in the middle of the night on Monday realizing what a Bad Idea it
> was to make the error that occurs when one accesses an undefined variable
> “uncatchable”.
>
> We can catch other kinds of programming error, such as requesting a method
> that does not exist, or indexing an array outside of its bounds.  Why should
> this one be different?
The motivation at the time was to prevent people using it as a bottom
or signal value (which was the kick you were all on then). Being able
to trap the error was regarded as a back door to null.
-Michael