Re: NULLs: theoretical problems?

From: V.J. Kumar <vjkmail_at_gmail.com>
Date: Sat, 25 Aug 2007 16:39:07 +0200 (CEST)
Message-ID: <Xns99976C5CFB2D4vdghher@194.177.96.26>

Jan Hidders <hidders_at_gmail.com> wrote in news:1188037788.486939.308150_at_i38g2000prf.googlegroups.com:

> On 25 aug, 02:13, "V.J. Kumar" <vjkm..._at_gmail.com> wrote:

>> Jan Hidders <hidd..._at_gmail.com> wrote
>> innews:1187998409.227306.271460_at_e9g2000prf.googlegroups.com: 
>>
>> > On 24 aug, 16:35, "V.J. Kumar" <vjkm..._at_gmail.com> wrote:
>> >> You may be right,  but then why the formula was not written with
>> >> an explicit 'and' ?
>>
>> > Because it does not satisify all the logical laws of an AND, so to
>> > avoid confusion another notation is used.
>>
>> What logical laws of AND are violated when we interpret
>>
>> 'def(x):f(x)'  as 'def(x) and f(x)' ?

>
> Commutativity and associativity.

What "Commutativity" ?

Does not 'f(x) and def(x)' evaluate to the same as 'def(x) and f(x)' would where def(x) is interpreted as a definedness predicate ?

What "associativity" ?

Does not 'def(x) and (x or y)' evaluate to the same as 'def(x) and x or def(x) and y' would where def(x) is interpreted as a definedness predicate ?

>
> -- Jan Hidders
>
Received on Sat Aug 25 2007 - 09:39:07 CDT