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On Monday 28 June 2004 23:18, Dan East wrote:
> Dimitris Papavasiliou wrote:
> > Indexing a nil value is undefined so you would expect
> > it to cause an error.
>   What if indexing a nil value returned nil instead of throwing an
> error?

Because usually indexing a nil represents a bug, and that behaviour would make 
tracking down such bugs extremely painful. You can't even make it optional 
once programmers start relying on 'nil propagation'.

In general, I think nil values are rather like gotos: they are occasionally 
expedient, but in general they lead to unmaintainable code, and so programs 
should usually be designed to avoid them. In time, I hope that nils will be 
removed from programming languages in the same way as gotos have been, and 
replaced with option types, as found in e.g. ML.

-- Jamie Webb