Re: NULLs: theoretical problems?

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