Gene Wirchenko wrote:
> On Fri, 10 Jun 2005 18:43:22 GMT, Jan Hidders
> <jan.hidders_at_REMOVETHIS.pandora.be> wrote:
>
> [snip]
>
>
>>Sometimes you *can* say something, even though some of the variables are
>>unknown. Suppose I told you x is a natural number, could you then tell
>>me whether the following statements are true:
>>
>> (x > 5) or (x <= 5)
>> (x - x) = 0
>>
>>I bet you could. :-)
>
> Your first example is equivalent to
> (x>5) or !(x>5)
> and is a case of excluded middle, but establishing that equivalency
> requires considering the internals of > and <=. That means that you
> can not use a truth table.
>
> Can you imagine the difficulty of figuring out all such possible
> interations of operators?
It's undecidable, even if you only consider equality as an operator,
which arguably doesn't have any internals. I already mentioned that
earlier on in the thread. So I'm not sure what exactly your point is here.
Received on Tue Jun 14 2005 - 01:58:54 CDT
