OpenEuphoria

1. Re: 'Unknown' and three-valued logic

• Posted by Juergen Luethje <jluethje at gmx.de> Nov 24, 2002
• 383 views

Pete wrote:
>> Unknown xor Unknown can be True or False

dm31 at uow.edu.au wrote:
> Hence, Unknown, since we are not sure which. :P

You are right!
In my truth table, I had written that Unknown xor Unknown = False.
That was not correct.

I checked it using the following formula:
a xor b = (a and (not b)) or ((not a) and b)
     <http://mathworld.wolfram.com/XOR.html>

Using "U" for "Unknown", the formula gives:
U xor U = (U and (not U)) or ((not U) and U) = U or U = U

Thank U!  

Best regards,
   Juergen