Hi Ralf, On 2018-02-28, Ralf Stephan <gtrw...@gmail.com> wrote: > The reason is apparently that the polynomial ring was not created by the > user on the command line but by the charpoly() code.
The parent of the pre-defined variable x wasn't created by the user either, so, please don't blame polynomial rings or the minpoly()/charpoly() code for it. sage: QQbar(sqrt(2)).minpoly().parent() Univariate Polynomial Ring in x over Rational Field sage: x.parent() Symbolic Ring > i would consider this a high priority bug. Is there a ticket? Not in the way you think, IMHO. One problem that I see is the fact that it is possible to create rings in which one variable name occurs twice, such as here: sage: RR['x']['x'] Univariate Polynomial Ring in x over Univariate Polynomial Ring in x over Real Field with 53 bits of precision sage: RR['x'].gen()-RR['x']['x'].gen() -x + x sage: _==0 False So, we have two x with different roles. It would make sense to disallow the creation of such rings. Also, I belive it is a bug that x is pre-defined as a symbolic variable; we should finally drop that pseudo-courtesy. Users mistake FAR too often symbolics with polynomials; by pre-defining x, we let the users believe that x is good for *all* computations. So, I believe it would be better to let the user create x him/herself, for the specific application that he/she has in mind. However, I am aware that I belong to a minority with that opinion. Best regards, Simon -- 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.
