Re: NULLs: theoretical problems?

From: Jon Heggland <>
Date: Mon, 27 Aug 2007 08:14:51 +0200
Message-ID: <fatq50$lpi$>

Quoth V.J. Kumar:
> Jon Heggland wrote:

>> . You still have
>> the excluded middle problem that V. J. Kumar complains about.

> No longer, it appears, there is a problem because Jan modified his
> definitions ! In the updated version, def(x) :(x or not x ) is now
> true for undefined x !

No. You are not paying attention. def(x):(x or not x) is false for undefined x. But it /is/ equivalent to def(x):true, which is /also/ false for undefined x.

> Likewise, def(x) : (x or true) is also true
> for undefined x,

No. def(x):whatever is always false for undefined x.

> so your surmise about the two SQL statements being
> different may be totallly off mark !
> It quite possible I misunderstood Jan's 'def(x) :true'. Who knows ?
> He may still be willing to present a coherent account of his DEF logic
> instead of feeding me with his punchy and petulant one-liners.

I surmise he is bored and impatient, since you seem determined to misunderstand something he considers very simple. And I sympathise.

Received on Mon Aug 27 2007 - 08:14:51 CEST

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