Steven D'Aprano wrote: > 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? > > Being Belgian, I suspect.
regards Steve -- Steve Holden +44 150 684 7255 +1 800 494 3119 Holden Web LLC www.holdenweb.com PyCon TX 2006 www.python.org/pycon/ -- http://mail.python.org/mailman/listinfo/python-list
