On Wed, Jan 1, 2014 at 2:17 PM, Peter Bruin <[email protected]> wrote:
> Hi Simon, > > >> I'd say this is (close to) a bug. >> > > It is a bug, without qualification. > Yes, it is a bug. So, we should think of being more precise, introduce "Set of partial maps >> from >> R to S", and use it as parents of partial maps that aren't maps. >> Similarly, one should more consistently distinguish between the set of >> all maps and the set of all morphisms. >> > > That seems to be the only reasonable solution. > We have this already: sage.categories.sets_with_partial_maps. But it looks like there are lots of places where it's not used appropriately: sage: ZZ.convert_map_from(QQ).parent().category() Category of hom sets in Category of rings > > I would like to add that in my opinion the first line of this example, > > sage: f = GF(11).convert_map_from(GF(7)) > > should not be assumed to work at all, and it would be preferable to raise > an error rather than returning something that is mathematically completely > arbitrary. > > Given the principle that no conditions are imposed on conversions (except > that if a coercion exists, the conversion equals the coercion), it should > in particular be perfectly fine if some of them do not satisfy the property > of existing at all. > > Peter > > -- > You received this message because you are subscribed to the Google Groups > "sage-devel" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/sage-devel. > For more options, visit https://groups.google.com/groups/opt_out. > -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/groups/opt_out.
