On Fri, 1 Mar 2024 at 10:04, Dima Pasechnik <dimp...@gmail.com> wrote:
> > > On 1 March 2024 09:07:26 GMT, 'Martin R' via sage-devel < > sage-devel@googlegroups.com> wrote: > >I'd be OK with raising an exception or with -oo, but it should be > uniform, > >and I think it should be the same for polynomials, Laurent polynomials > and > >in the same spirit for degree and valuation. > > > >It might be best to raise an exception, because this ensures that the > zero > >polynomial gets special treatment. > > Exceptions are expensive, performance-wise, and using them as a regular > means of controlling the flow of the algorithm execution is not a good idea. > A simple if/then/else is much cheaper. > Isn't this suggestion to have f.degree() raise an exception when f is zero, but also then that any code which needs the degree to treat 0 as a special case (where that makes sense)? To it would be the caller's responsibility to do that with a test of f.is_zero() or whatever, rather than by seeing if an exception is triggered. John > > Dima > > > >Martin > >On Thursday 29 February 2024 at 22:54:20 UTC+1 Nils Bruin wrote: > > > >> On Thursday 29 February 2024 at 11:15:21 UTC-8 Dima Pasechnik wrote: > >> > >> How about using something like > https://github.com/NeilGirdhar/extended_int > >> ? > >> (Even better, do a PEP to have such a thing in Python proper...) > >> In old, totally duck-typed, Python this didn't really matter, but > nowadays > >> it does make > >> a perfect sense. > >> > >> At the moment, I think most degree functions do their best to return > sage > >> Integer objects; mainly so that coercion works well with them. So > whatever > >> solution we use should probably be based on objects that naturally live > in > >> the sage hierarchy. We do have an infinity object in sage and it > already > >> gets used for valuations. > >> > >> Incidentally: > >> > >> sage: R.<x>=LaurentSeriesRing(QQ) > >> sage: z=R(0) > >> sage: z.valuation() > >> +Infinity > >> sage: z.degree() > >> -1 > >> > >> I don't quite know why laurent series have a degree defined at all, but > >> they're keeping to the deg(0)=-1 convention. > >> > >> Incidentally: > >> > >> sage: A.<x>=QQ[] > >> sage: B.<y>=LaurentPolynomialRing(QQ) > >> sage: x.valuation(oo) > >> -1 > >> sage: y.valuation(oo) > >> 1 > >> so polynomial rings have a valuation (that will return +oo when > >> appropriate), but on LaurentPolynomialRing this gets silently broken: > the > >> argument simply gets ignored and the valuation at 0 is returned. So I > guess > >> you can get a well-behaving degree with > >> > >> f=0*y > >> -f(1/y).valuation() > >> > > > > -- > 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 sage-devel+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sage-devel/D20DACD9-8D5A-48F4-81F5-141CF0181BA1%40gmail.com > . > -- 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 sage-devel+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/sage-devel/CAD0p0K45r2ishqx4kzEwuVF9%3DYDtojjteBn3snKMkGj8ijb72g%40mail.gmail.com.
