[Grace-core] Undefined Variables

[Kim Bruce]

It sounds like one of those things that will be available, but not made prominent, that is mainly there for tools to use.  (Perhaps we could even issue a warning in any program that uses it.)  At any rate, while I would discourage students from using it, it seems useful for building tools.  It's OK to me tao have it raise an exception.

Kim



> On Feb 25, 2015, at 1:37 PM, Michael Homer <mwh at ecs.vuw.ac.nz> wrote:
> 
> 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
> 
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