Jon Heggland schrieb:
> In article <1134926774.703015.67240_at_z14g2000cwz.googlegroups.com>,
> boston103_at_hotmail.com says...
>
>>Sure, a one-argument predicate like 'is_null', or 'is_odd', talks
>>about a property/attribute and can be called an 'adjective'. But the
>>'is_null' predicate cannot help one answer the question "what is '+' in
>>'2 + NULL' ?". So, what is '+' in the expression and how does one
>>interpret such expression ?
>
>
> "2 + NULL" isn't a valid expression. (Well, it is in SQL(?), but I don't
> think it should be, and I won't try to justify it.)
2 + NULL = 2
Just remove NULL because it is a flag to denote a non-existing thing
(which exists in other dimensions but does not exist here in the current
dimension). So there are neither formal nor informal problems with this
expression if we provide correct interpretation of NULL. Notice that
NULL here (and always) in not number 0. In the expression 2+NULL we do
not apply the operation at all, while in 2+0 we do apply the sum operation.
--
http://conceptoriented.com
Received on Mon Dec 19 2005 - 03:45:49 CST
