Christoph Zwerschke wrote: > Bryan Olson schrieb: > >>> Still think there is no such thing? >> >> >> Uh, yes. >> >> The Cartesian product of two sets A and B (also called the >> product set, set direct product, or cross product) is defined to >> be the set of [...] >> >> All sets, no strings. What were you looking at? > > Not only sets.
Snipping is not going to make the facts go away. I did not choose the reference at issue in this strand: http://mathworld.wolfram.com/CartesianProduct.html > This goes on (anyway "everything is a set"). The claim "everything is a set" falls into the category of 'not even wrong'. Whatever semantics Python adopts, it must be well-defined. Watch things not be sets: x = [1, 1, 2] y = [1, 2] print x == y print set(x) == set(y) > You can also > have the Cartesian product of functions. And you can think of a string > as a function from a countable index set I to the set of all characters > C. So the Cartesian product of two strings will become a function from > IxI to CxC. Since IxX is countable again, this is equivalent to a tuple > of 2-tuples of characters which you can also interpret as a tuple of > strings with 2 chars: > > "ab" x "cd" = ("ac", "ad", "bc", "bd") I really did try to raise the real issues. I cannot make you answer, but the question remains: are duplicate and order significant in what you call "Cartesian product" or they not? Can you show that your proposed language extensions are useful and consistent in some reasonable sense? > Do I have eliminated all remaining clarities now? :-) Yes. Good one. Sure. -- --Bryan -- http://mail.python.org/mailman/listinfo/python-list