On 03/30/16 at 03:55pm, Marko Rauhamaa wrote: > Manolo Martínez <man...@austrohungaro.com>: > > > On 03/30/16 at 02:44pm, Marko Rauhamaa wrote: > >> I don't even know if you can say much about the cardinality (or > >> countability) of mappings. The general set of mappings can't exist. > >> The *class* of mappings does exist in some set theories, but I don't > >> believe classes have cardinality. > > > > I guess I was thinking of the cardinality of the set of tuples with > > members of the domain in the first member and their image in the > > second. > > If you fix the domain and codomain, then we can discuss cardinality > again, but the answer depends on the domain and codomain. For example, > if the domain is the empty set, there exists precisely one function. And > if the codomain is the empty set as well, that function is a bijection.
Yeah, what I said and you quote above is wrong: I was thinking of the cardinality of the set of those sets of tuples. This seems like the kind of thing that would result in set-theoretic paradoxes, so yes, you are probably right that the cardinality of mappings is not well defined. Manolo -- https://mail.python.org/mailman/listinfo/python-list
