[plt-scheme] [OT] grateful for PLT Check Syntax

Sorry for telling that, but that story has nothing to do with PLT's 
Check Syntax. For nearly all languages, reference to an undefined 
variable is a compile time error. But this is not true for Computer 
Algebra Systems(CAS). Even with no values bind to variable `x', a CAS 
should still reduce `x+x+x' to `3x', which implies reference to an 
undefined variable is not an error. But CAS do have their merits.

Chongkai

Geoffrey S. Knauth wrote:
> A colleague running experiments in Mathematica recently found that 
> some of his extraordinarily good results were due to a misspelled 
> variable.
>
> datalengh = Length[data];
>
> Later in the code, datalength was not misspelled, but it had no 
> value.  The program was happy when it should not have been, and it 
> produced happy pill results.  I listened to the story and thought, 
> "This could not have happened with DrScheme."
>
> Geoff
>
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