Re: NULLs: theoretical problems?

On 27 aug, 05:26, "V.J. Kumar" <vjkm..._at_gmail.com> wrote:
> Jan Hidders wrote:
> > On 25 aug, 16:32, "V.J. Kumar"
> > > Clearly, 'def(x):(x or not x') is allowed [...]
>
> > ... and is indeed equivalent with 'def(x):true'.
>
> According to your own definition, 'def(x) : f(x)' evaluates to 'false'
> whenever x is not defined. So f(x) in 'f(x) = x or not x' must be
> 'false'.

I really have no idea why you think that.

> > > Likewise, 'def(x):(x or true)'
>
> > ... and is indeed equivalent with 'def(x):true'.
>
> This is interesting. Just a little while ago, you complimented Jon
> for his understanding that 'select * from table where def(x): (x or
> true)' is equivalent to 'select * from table where x is not null and
> (x or true) '. Apparently, at the time you thought that 'def(x) :(x
> or true) ' should evaluate to 'false'. It seems that now you think
> that it should evaluate to 'true' !

Not really. The formula 'def(x) : true' does not evaluate to true if x is undefined.

• Jan Hidders