I don't understand - `degree` doesn't make much sense for Laurent series - there is no way to determine the degree of a LaurentSeries and no way to determine the degree of a LazyLaurentSeries with one minor exception - which is when it is known that the series terminates, but that's rare.
On Friday 1 March 2024 at 18:49:15 UTC+1 Giacomo Pope wrote: > Following this discussion, I have made a draft PR to change the degree for > *only* the LaurentPolynomialRing and I will see if the CI detects anything. > > https://github.com/sagemath/sage/pull/37513 > > I agree that if we change the LaurentPolynomialRing we should also change > the `LaurentSeriesRing`, at the moment `LazyLaurentSeriesRing` has no > method `degree()` but *does* have a `valuation()` method... so this is odd. > > On Friday, March 1, 2024 at 5:29:53 PM UTC Martin R wrote: > >> Could you expand on 'the whole valuation interpretation of "degree" goes >> out of the window'? What do you mean with "valuation interpretation"? >> >> Is raising an exception out of the question? >> >> On Friday 1 March 2024 at 18:11:40 UTC+1 Nils Bruin wrote: >> >>> On Friday 1 March 2024 at 04:26:43 UTC-8 Dima Pasechnik wrote: >>> >>> >>> It seems that exactly the same algorithm will work (I didn't check >>> this!) for Laurent polynomials (they still form a Euclidean domain), and >>> there you better set degree(0)=-oo, otherwise it's going to be a problem. >>> >>> I think it's been established >>> that LaurentPolynomialRing(QQ,'x').zero().degree() == -1 is problematic. >>> With the definition that (1/x).degree() == -1 it clearly is. >>> >>> I think the question is more: do we have enough evidence that setting >>> degree(0) == -oo for *all* polynomial rings is significantly better (if >>> better at all) that it's worth the pain and incompatibilities that would >>> ensue from changing the rest of sage as well? That's not so clear to me. >>> From the perspective of multivariate polynomials, the whole valuation >>> interpretation of "degree" goes out of the window, so there "-1" is largely >>> available and quite possibly used extensively by the underlying libraries. >>> >>> I guess one could see what happens if the change is made to Laurent >>> polynomials (and Laurent series as well, perhaps?). Based on how that goes >>> one could re-evaluate degrees of 0 polynomials in other polynomial rings. >>> >>> Alternatively, we could deprecate degree on them in favour of using >>> valuation-inspired terms instead, where the extension val(0)=oo is more >>> universal. As Oscar's example in Matlab shows, the concept of degree gets >>> (mis)used for other, more implementation-oriented definitions as well, so >>> perhaps the term should just be avoided for Laurent polynomials. >>> >> -- 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/b6ede155-fb29-4607-be7b-b028ce39e973n%40googlegroups.com.
