# Re: NULLs: theoretical problems?

Date: Mon, 20 Aug 2007 08:39:55 -0000

Message-ID: <1187599195.269472.153110_at_a39g2000hsc.googlegroups.com>

On 20 aug, 01:48, "V.J. Kumar" <vjkm..._at_gmail.com> wrote:

> Jan Hidders <hidd..._at_gmail.com> wrote in news:1187555898.287393.128980

*> _at_a39g2000hsc.googlegroups.com:
**>
**> > Such a construct also makes clear how the rules of logic can or cannot
**> > be applied. For example, what now looks at first sight like a
**> > tautology, namely "t.a < 5 or t.a >= 5", would then look like either
**> > "(DEF t.a : t.a < 5) OR (DEF t.a : t.a >= 5)" or "DEF t.a : (t.a < 5
**> > OR t.a >=5)". Both are equivalent with "DEF t.a : TRUE" but not with
**> > "TRUE". The logical rules for reasoning with this construct are not
**> > that difficult to see, and it avoids something like 3VL.
**>
**> > -- Jan Hidders
**>
**> I wonder what the truth tables for 'AND' and 'OR' would look like with
**> the DEF operator. Could you show those tables ?
*

They would be the usual table you already gave:

*> x y AND
**> -------
**> defined
**> 0 0 0
**> 1 0 0
*

> 0 1 0

*> 1 1 1
*

- Jan Hidders