Miller, Hugh wrote:
From: Moritz Lenz [mailto:[EMAIL PROTECTED] [EMAIL PROTECTED] wrote:
Technically the Cartesian cross operator doesn't have an
identity value.
It has.
The set which contains only the emty set, or in perl terms ([]);
Or am I missing something?
Should be a (any) 1 point set for the identity.
How about considering models from category theory, rather than set
theory ? Seems much more fruitful for computer issues than set theory.

No an identity would be a set E such that for any set A: A x E = A, but no such set exists. A singleton set get close, but the result is only isomorphic (there is a natural bijection) not equal. Even in category theory you only get isomorphism.


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