thanks for the explanation, and yes, I agree that there is a problem - I have no good idea to fix it, though. In fact, looking at my code with this in mind, it looks particularly stupid: already the first call to "order" should be avoided, I should simply check whether g has a constant term.
After that, we are probably out of luck, because, as you said, recognising the zero power series is not possible. On the other hand, if g is zero, calling code should not expect divide to succeed anyway. I admit I am rather on the "immediate progress" side Martin Am Mittwoch, 23. Januar 2019 17:50:51 UTC+1 schrieb Waldek Hebisch: > > Martin R wrote: > > > > Dear all! > > > > the question fits into the title :-) > > > > Does not fit: it is truncated by many viewers. Fixed: > > > shouldn't UTS(F, x, 0) export EuclideanDomain if F is > > a Field? > > That is a tricky question. I see that you gave an > implementation, but there is a core problem: > EuclideanDomain implies BasicType and this already > is a lie. That is equality for power series is > noncomputable. Which means that generic algorithms > may have very poor performance or fail. To explain > it better, consider Gaussian elimination applied > to invertible matrix of power series. Generic algorithm > will struggle trying to find out if an element is suitable > pivot. Algorithm aware of power series will try increasing orders > and checking all elements of a column for given order. > In this way it will find pivot of best order, without > wasting time examining many entries of zero or nearly > zero series. > > So question is if after lying several times we want > to keep lying, or if we want to clean up things. > Pragmatically lying may look attractive as it gives > immediate rewards, while punishment is delayed. > OTOH most had to fix bugs comes from original developers > ignoring problems and opting for immediate "progress". > > -- > Waldek Hebisch > -- You received this message because you are subscribed to the Google Groups "FriCAS - computer algebra system" 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]. To view this discussion on the web visit https://groups.google.com/d/msgid/fricas-devel/5329f69d-9b98-4333-a70e-acc438c25f69%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
