On Thu, 2 Apr 2009, Steven D'Aprano wrote: > On Thu, 02 Apr 2009 04:23:32 +0000, John O'Hagan wrote: > > Beyond being part of a conventionally-ordered set of keys, what can an > > ordinality of zero actually mean? (That's a sincere question.) >
[snip erudite definition of cardinality] > For non-infinite sets, you can treat ordinal numbers and cardinal numbers > as more or less identical. So an ordinality of zero just means the number > of elements of something that doesn't exist. This is the bit I don't get - I had thought of ordinality as something attached to each item - ['a','b','c'] has a cardinality of 3, and elements of ordinality 1, 2 and 3 (first,second, third) respectively. So it's possible to have a cardinality of zero (an empty sequence does) but only "something that doesn't exist" can have an ordinality of zero; as soon as there is an item, its ordinality is 1. Shoot me down, please! > How that relates to whether indexing should start at one or zero, I have > no idea. Only insofar as the "weirdness" of indexing being out of step with ordinality/cardinality matters, i.e. not that much. :) John -- http://mail.python.org/mailman/listinfo/python-list
