On Sun, 22 Nov 2009 15:08:28 +0000, Duncan Booth wrote: > n00m <n...@narod.ru> wrote: > >> And now it's elephants instead of vectors. Def: an elephant is smarter >> than another one IIF its size is strictly less but its IQ is strictly >> greater >> >> I.e. you can't compare (2, 8) to (20, 50) or let count them as equally >> smart elephants. > > and that still isn't a relationship where you can get any meaningful > order out of sorting them:
Not everything has, or need have, a total order. There are relationships which are only partial (i.e. not all the items are comparable), or missing transitivity. A real-world example is pecking order in chickens, or social hierarchies in general. Using the > operator to mean "higher ranking", you often get non-transitive hierarchies like the following: A > B, C, D, E B > C, E C > D, E D > B, E That is, A > B > C > D > E except that D > B also. Economic preference is also non-transitive: people may prefer X to Y, and prefer Y to Z, but prefer Z to X. It is perfectly legitimate to sort a non-total ordered list, provided you understand the limitations, including that the order you get will depend on the order you started with. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
