On Tue, 25 Oct 2005 10:09:29 -0400, Christopher Subich wrote: >>>By analogy, one can ask, "is the cat inside the box?" and get the answer >>>"No", but this does not imply that therefore the box must be inside the >>>cat. >> >> >> Bad analogy, this doesn't define a mathematical ordering, the subset >> relationship does. > > Yes, it does. Consider "in" as a mathematical operator: > > For the set (box, cat-in-box) > > box in box: False > box in cat-in-box: False > cat-in-box in box: True > cat-in-box in cat-in-box: False > > For the set (box, smart-cat) # cat's too smart to get in the box > > box in box: False > box in smart-cat: False > smart-cat in box: False > smart-cat in smart-cat: False > > In both these cases, the "in" operator is irreflexive, asymmetric, and > transitive (extend to mouse-in-cat if you really care about transitive), > so "in" is a partial order sans equality. A useless one, but a partial > order nonetheless.
What do you mean "in" is a useless ordering? It makes a huge difference whether "nuclear bomb in New York" is true or not. In fact, I'm quite surprised that Antoon should object to "in" as "this doesn't define a mathematical ordering, the subset relationship does" when "subset" is just "in" for sets: set S is a subset of set T if for all elements x in S, x is also in T. Informally, subset S is in set T. Can somebody remind me, what is the problem Antoon is trying to solve here? -- Steven. -- http://mail.python.org/mailman/listinfo/python-list