On 22 October 2016 at 17:28, Vincent Delecroix <20100.delecr...@gmail.com> wrote: > On 22 October 2016 at 16:10, Ralf Stephan <gtrw...@gmail.com> wrote: >> On Saturday, October 22, 2016 at 4:04:55 PM UTC+2, John Cremona wrote: >>> >>> So Ralf, do you want to catch the case where the exponent in QQbar is >>> actually rational and then do what QQbar already knows how to do >>> (raise to a rational power), returning an element of QQbar; and raise >>> an Error of some kind in the other case? >> >> >> Exactly, if noone is objecting. > > I am strongly objecting. The behavior of any operation in Sage is that > the parent of op(a, b) should only depend on the operator op, > parent(a) and parent(b). Powers are a bit special but not enough to > use conversion instead of coercion.
Counterexamples: sage: parent(RR(1).sqrt()) Real Field with 53 bits of precision sage: parent(RR(-1).sqrt()) Complex Field with 53 bits of precision and: sage: parent(QQ(1).sqrt()) Rational Field sage: parent(QQ(2).sqrt()) Symbolic Ring > > What can be done is that pow(a, b) with paren(a) = ZZ and parent(b) = > QQbar can go to SR where everything might be defined. > > -- > You received this message because you are subscribed to the Google Groups > "sage-support" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sage-support+unsubscr...@googlegroups.com. > To post to this group, send email to sage-support@googlegroups.com. > Visit this group at https://groups.google.com/group/sage-support. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at https://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
