Cartesain product with the empty set is empty.  A x B is the set of all pairs 
(a,b) where a is in A and b is in B. If either is empty then there are no such 
pairs and the result is also empty.

--
Mark Biggar
[EMAIL PROTECTED]
[EMAIL PROTECTED]
[EMAIL PROTECTED]

 -------------- Original message ----------------------
From: TSa <[EMAIL PROTECTED]>
> HaloO,
> 
> why is (1,2,3) X () defined to be the empty list
> and not (1,2,3) as is the case with the cartesian
> product of sets which X basically is with preserved
> order.
> 
> Regards, TSa.
> -- 
> 
> The Angel of Geometry and the Devil of Algebra fight for the soul
> of any mathematical being.   -- Attributed to Hermann Weyl

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