The problem of "<" not providing a total ordering seems to come up again and again in different situations. There are two cases now already where it is clear that even in Python "<" does not signify a total ordering anymore:
- python complex numbers ( < gives an error) - python sets ( < denotes proper inclusion) Rather than keep trying to work around this by trying to impose rather arbitrary total orderings in categories, wouldn't it be more natural to recognise that sorting doesn't make canonical sense in all categories and be explicit about the choice of injection from the set to be sorted into a totally ordered set? The "key" attribute for sort allows for exactly such a choice. sage: L=[set([1,2,3]),set([3,2]),set([1,4])] sage: L [set([1, 2, 3]), set([2, 3]), set([1, 4])] sage: L.sort() sage: L [set([2, 3]), set([1, 2, 3]), set([1, 4])] sage: L.sort(key=lambda V: [len(V),sorted(V)]) sage: L [set([1, 4]), set([2, 3]), set([1, 2, 3])] sage: L.sort(key=lambda V: sorted(V)) sage: L [set([1, 2, 3]), set([1, 4]), set([2, 3])] -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
