Re: In praise of 'nil' (Was: Proposal for table length operator

[David Kastrup <dak@...>]

Dirk Laurie <dpl@sun.ac.za> writes:

> On Wed, Dec 15, 2010 at 08:54:59AM +0200, Axel Kittenberger wrote:
>> >    What happened before the Big Bang?  Nil.
>> 
>> As empiricist I must say, no. We don't know. Might been Nil, might
>> been something else. Currently no way to guess.
> Exactly my point, actually.  
>
> "nil" in lua means "not one of the possibilities that we know 
> something about".

Huh?  nil is a very specific value with very specific properties.

> There is no distinction between something unknown and something
> non-existent.

nil is neither.

> For example, if I say 
>     for i=1,10 do print a[i] end
> and some of those a[i]'s print 'nil', I am not given the information
> of whether that 'nil' is stored as such in the array part, or is just
> missing from the hash part.

nil is the default value of array elements.  That does not make the
value unknown or non-existent.

-- 
David Kastrup