On 29 April 2014 16:17, Nils Bruin <[email protected]> wrote: > On Tuesday, April 29, 2014 7:47:39 AM UTC-7, Volker Braun wrote: >> >> Always putting things in canonical form will be slow (there is no hook for >> "you are about to be put into a set") and/or not possible (fp group >> elements). > > > I disagree in this particular case. Making the denominator monic is *much* > cheaper than doing the GCD computation for removing common factors from > numerator and denominator. And for fields like this, it help keeping > unnecessary coefficient explosion in check, so it may actually be faster in > some cases. > > There is a more problematic issue. If you construct: > > sage: O=K.maximal_order() > sage: Pu.<u> =PolynomialRing(O) > sage: Ku.<u> = FractionField(Pu) > > you get an isomorphic field (and over ZZ this is can even be good idea: keep > coefficients denominator-free), but it's no longer possible to make > denominators always monic.
That is true. In my code I construct function fields like QQ(u) as the field of fractions of ZZ[u] for this reason, but sometimes have to base change up to a number field. (If I say much more then Nils will be able to guess what computation I am doing! Hint: modular curves.) In #16268 I only propose to change the reduce method for the class 'sage.rings.fraction_field_element.FractionFieldElement_1poly_field' which will unfortunately not solve the issue of sets of elements from fields constructed as in your example. One thing at a time... John > > -- > 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 [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://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 [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
