Here is a quick patch for one of the listed issues: http://trac.sagemath.org/ticket/19538 S.
* Travis Scrimshaw <tsc...@ucdavis.edu> [2015-11-04 16:37:17]: > Hey Salvatore, > > first of all thank you for your answer, it looks like you are one of > the > person I pester the most with these issues. > > I think I'm the one who knows the most about this because I have made > the most recent additions and fixes to that part of Sage (although I'm > happy to be wrong on this point). > > As far as gcd business goes my point is not that the current > behaviour is > necessarily wrong but it is inconsistent. What I mean is that > sage: L = LaurentPolynomialRing(ZZ, 'x0,x1,y0,y1') > sage: R = LaurentPolynomialRing(LaurentPolynomialRing(ZZ, 'y0,y1'), > 'x0,x1') > mathematically should be (almost) the same object but > sage: L.inject_variables() > Defining x0, x1, y0, y1 > sage: (x0+1)/(x0+1) > 1 > sage: R.inject_variables() > Defining x0, x1 > sage: (x0+1)/(x0+1) > (x0 + 1)/(x0 + 1) > Their fraction fields are indeed different but elements belonging to > both > should have the same properties. This is not the case at the moment: > sage: L = L.fraction_field() > sage: R = R.fraction_field() > sage: L.inject_variables() > Defining x0, x1, y0, y1 > sage: (x0+1).gcd(x0+1) > x0 + 1 > sage: R.inject_variables() > Defining x0, x1 > sage: (x0+1).gcd(x0+1) > 1 > I agree with you that a rewrite might not be a good use of anyone's > time so > we should start bug hunting first.  I will open a ticket with the > last of the > issues I pointed out in my previous e-mail as soon as I can find a > solution. > > I suspect it all comes down to defining a gcd of the multivariate > Laurent polynomial ring and this fixing the issues. Although this may > not be the only problem because of the fact that these fraction fields > are different. I think this is true even mathematically speaking as one > is rational functions in x0, x1, y0, y0, with coefficients in ZZ and > the rational functions in y0, y1 with coefficients in the Laurent > polynomial ring x0, x1 over ZZ as (y0 + y1) / (y0 - y1) is not in the > latter I believe. > > One design question: can someone explain to me the rationale of > having two > implementations for Laurent polynomials (one univariate and one > multivariate) > and then a wrapper factory function on top? If the idea is that some > methods > are defined only in special cases would it not be easier to add them > at > __init__ time with something like > self.mymethod = MethodType(mymethod, self, self.__class__) > This would allow to expose directly two classes > LaurentPolynomialRing and > LaurentPolynomial instead of a factory function. > >   I see two big reasons. The first is speed and memory efficiency > because the internal structure of the univariate is more simple than > the multivariate. The second is there are more algorithms/methods for > the univariate (which is an argument for subclassing, or at least > possibly separating out common functionality into an ABC). > Best, > Travis >  -- 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 post to this group, send email to sage-devel@googlegroups.com. Visit this group at http://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
